THE VARIED ROLES OF SNAILS - National Universities Commission

THE VARIED ROLES OF SNAILS (GASTROPOD 

MOLLUSCS) IN THE DYNAMICS OF HUMAN 

EXISTENCE 

Mr. Vice Chancellor Sir, 

Distinguished Colleagues 

Ladies and Gentlemen, 

Lions and Lionesses. 

1. INTRODUCTION: 

BY 

PROF. FABIAN C. OKAFOR 

1.1 PREAMBLE. 

It gives me tremendous pleasure to stand before you to 

make this presentation today. I give God all the glory for 

this his marvelous act. In the eyes of man, this would have 

been impossible, but the Creator of the Universe in His 

mercies has given me this opportunity. 

My family and I are very grateful. I would like to thank the 

Vice Chancellor for rushing to my aid when I was in very 

deep health problem. He stood by me with his lieutenants 

in a manner that left me dumbfounded and today I celebrate 

the outcome of their Kindness by being part of this glorious 

event- the University of Nigeria Inaugural Lecture. 

I am proud to be a Professor of Zoology, serving in this 

University and I have thoroughly enjoyed this my chosen 

area of competence that has opened wide the divine chest 

1

of knowledge to me, as I go about conducting research in 

areas as wide apart as diagnostics, physiology, 

environmental toxicology, parasitic infections, 

epidemiology and other branches of applied Biology. By 

specialization I am a Parasitologist a field as wide as 

Biology in itself. So for me to choose a topic for the 

inaugural lecture is a very difficult one. However in course 

of my studies I noticed that snail always recur in my work 

and I also know, they are eaten in some areas and some 

control it, either because they are known intermediate 

hosts of human disease parasites, or they devastate crops 

and so are important pests in agriculture. I settled to deal 

with these organisms that my friend Dr Obi Udengwu 

always refer to as “Mpioro” Today, together we are going 

to look at the roles of the snails in the dynamics of human 

life. At the end we will judge whether the Gastropods are 

friends or foes; and whether they have any thing to offer to 

humans as we march on in our quest for survival. 

1.2 DYNAMICS OF HUMAN LIFE 

The dynamics of human life involves overcoming 

population pressures and the degradation of the planet 

Earth. It also revolves around nutrition, health, industrial 

development and other responsible activities that lead to 

the stable socio-economic development and aesthetics of 

life. Dating back to several million years ago, the 

population of the world was very low, and then later it 

grew very slowly. In the beginning, the number might have 

been three to ten million people on earth. In the first 

millennium after Christ, there might have been about two 

hundred and fifty million. Five hundred million was the 

population reached around 1650, one thousand million in 

2

1820 and twice that in 1930 (Martins, 1983). There are now 

more than six Billion people. This population growth is not 

without setbacks such as childhood mortalities due to 

diseases and malnutrition, fertility problems and many 

other demographic transitions. Despite these, population 

growth today is still rapid and exponential. Survival 

became linked to social, agricultural, technical and 

economic development. These result in the environment 

being bedeviled with such problems as deforestation, 

overgrazing, erosion, desertification, urban expansions, 

population changes, climatic changes and global warming. 

Features that have produced individuals faced with several 

harmful side effects like, high population density, high 

consumptions, excessive use of non-renewable resources, 

the accumulation of wastes, pollution and the deterioration 

or destruction of the natural environment. As the years 

progress, stagnation of socio-economic development stirs 

man in the face. This situation, in conjunction with the 

increase in population, make it clear that man is heading for 

catastrophe even faster than expected, unless he starts to 

deal with these problems by not further destroying the 

ecological support systems but rather enhancing their 

responsible exploitation, renewal and protection. 

The problems with the dynamics of human life lie in the 

following two processes: 

(a) the initial productive potential of the earth 

accommodated population growth but the demands of 

the population exceeded the potential sustainable 

harvest, so that biological and ecological reserves are 

increasingly exhausted; 

3

(b) the consumption in the system is reduced when the 

ecosystem collapses with disastrous consequences 

such as malnutrition, morbidity and mortality. 

Complex and big changes occur in the ways man pursued 

his life, his methods of production and exploitation of his 

resources. For instance, the universal demand for food, 

clothing, shelter and other comforts of life, prompted the 

creation of many new things including new ways of using 

biodiversity around. Gastropods (i.e. snails) are one of the 

organisms that have co-existed with man which over the 

years have found itself playing several roles to meet the 

needs of man in a variety of ways. Scientists observed that 

everyday life throws more than a million opportunities in a 

man’s way but he tries to make the most of each one that 

may be accessible. In the case with snails, every 

opportunity to be useful to man is being harnessed and 

consummated. 

1.3. MAN – SNAIL INTERACTIONS IN NATURE 

Man and Snails have associated intimately in nature from 

antiquity. The interactions between them have been 

recognized from the earliest times. These interactions 

became very prominent during the height of the Roman 

Empire when it was a common practice to eat Snails in the 

courts of the Emperor where they are used as aphrodisiac 

(Taylor, 1900). The high nutritive value of snail meat was 

later publicized by Leger in 1925 and Moretti in 1934. The 

true nature of snail meat was discussed in a Symposium 

paper where it was stressed that “snails were neither fish 

nor flesh; and that their consumption was permitted on 

meatless days in Europe (especially during lent), whereas 

they are avidly consumed in the rural tropical areas”. The 

4

contributions of snails to human existence have been a 

subject of several debates and research evaluations. As far 

back as 1890 studies such as those of Locard in 1890, Rust 

in 1915, Boisseau and Lonorville in 1931, Arnould in 1933, 

Kaibo in 1935, Ri in 1935, Maubert in 1943, Pardo in 1943, 

Metteo in 1946, Jutting in 1952 and Cadart in 1955, 

attracted great attention to the snails and their benefits. The 

matter is still a topic being discussed in several rural 

development and poverty alleviation forums today. The 

scientists all agree that snails and man live together and 

have some dependence that exerts fundamental influences 

on the survival of both groups. 

Gastropods, as snails are known, belong to the biological 

Taxon called Mollusca. These belong to the animal 

kingdom. They are conspicuous invertebrates that have 

their soft bodies covered with calcareous shells and are 

very successful in nature. They live in a wide range of 

ecosystems from swamps, ditches, ponds, rivers, lakes, 

forests, gardens to farm lands. Not every member of this 

group has similar preferences, structure or behaviour. 

1.4. DOMESTICATION OF WILD SPECIES 

As far back as 12,000 years ago, man started the journey 

into utilizing domesticated wild species of animals 

including snails. The process of looking to the wild in the 

quest for animals to be used for either medicine or food, 

was then guided by certain fundamental demands of human 

societies, especially, the need to obliterate hunger, to solve 

transportation problems and to do haulage work. In meeting 

these needs, man resorted to using wild animals and their 

products in a variety of ways that suited his existence 

(Afolayan, 1980). Several hundreds of thousands of wild 

5

animals were evaluated over time till we arrived at the 

present few that are intricately woven into human ecology 

and food security. 

Man categorized wild animals into: 

(a) Conventional mainframe species such as cattle, 

sheep and goats, which are too large, requiring 

too much expense and space; 

and 

(b) Mini-frame species such as rodents, 

grasshoppers, termites, maggots, earthworms, 

and snails that are increasingly playing important 

roles in human nutrition and other activities. 

The latter are tiny, user friendly “species and are becoming 

more attractive now as potential farm animals. They lend 

themselves to economic niches that are not easily filled by 

large main-frame livestock. Much of their potential is for 

subsistence production, for the benefit of peasants and the 

poorest people in rural communities that have found 

themselves outside the cash economy (Asibey and Child, 

1990). These resources have indirect contributions to 

human food security as follows: 

a). income generation, e.g. in tourism and recreation; in 

hunting; in bush meat trade; in sales of trophies, skins, 

and hides. 

b). in live animal trade, in spiritual health, in physical and 

mental health and in forestry/agriculture. 

Wild life production falls into three categories: 

6

a.) Production from the wild (wild catching of 

animals.). 

b.) Wild ranching 

c.) Wild farming and domestication. 

d.) Production from the wild (wild catching of 

animals.). 

e.) Wild ranching 

f) Wild farming and domestication 

Domestication of wild animals is encouraged for meat 

production to improve protein supply (Martin 1983; Muir, 

1989; and Ajayi, 1979). Works on snails have been carried 

out in West Africa for a long time.. Among these, snail 

farming has been projected to have the potential for playing 

an important role in the life of man, especially when 

developed into commercially viable and sustained industry, 

using simple technical know – how and cheap methods of 

production (Ajayi and Tewe,1983; Asibey). 

2. General Features of Molluscs: 

All molluscs must have: food, oxygen and moisture to be 

alive. Most molluscs live in the ocean or, if on land, in 

moist places such as under leaves or in soil, some need a 

sandy, ocean environment. All molluscs require moisture to 

stay alive. The desert dwelling snails are no exception as 

they maintain their own moisture inside their shell by 

means of a trap doors and or a mucus plug. 

Many molluscs eat: plants (herbivores) or plant cell 

materials in the water. Terrestrial snails like to eat fresh 

leaves and decomposing materials. This can be beneficial 

because they break down decomposable materials, but 

7

snails can also become pests when they turn their attention 

to garden crops and vegetables. Many water molluscs eat 

mosses, algae and such other microscopic plants. 

Some molluscs are carnivores (eating such things as fish 

and other molluscs) and some are even parasites (living 

within another living host) 

Most aquatic molluscs filter oxygen from the water to 

“breathe” by means of gills. Terrestrial and some pond 

snails breathe using lungs (Pulmonary sacs). Some pond 

snails have both gills and modified lungs. Deep ocean 

trenches have molluscs that are anaerobic. 

Polluted waters lack oxygen and food for molluscs to eat 

and “breathe”. This makes them sick and they die and the 

eggs fail to hatch or the juveniles would not live long. . 

Most molluscs can be eaten by man. Some of our favorites 

are scallops, oysters, clams and “escargot” (land snails - 

Helix , Achatina, Archachatina.) 

Many people collect shells for their beauty and interesting 

shapes. People who study the shells are called 

Conchologists. Those scientists that study the molluscan 

animal are called Malacologists 

Shells have long been used by man as tools, and buttons, 

jewelry (pearls and cameos), etc. 

Dyes can be produced from shells for use in colouring 

cloth. This is not so important today as we have much 

cheaper synthetic dyes.. 

Molluscs can be found in gardens, in ponds, deserts and 

oceans. Some live in the tops of trees and others high in the 

mountains. 

8

Gastropods I: Terrestrial or Garden Snails: 

Fig .1 Achitina achatina ( African Land Snail) 

Terrestrial gastropods often have a shell to protect their soft 

body. Some like slugs have no shells. 

The body of the snail is usually moist and often slimy. 

Snails have tentacles with eyes on the ends. They have a 

very developed sense of smell, but do not feel much 

sensation/touch-wise. They do not hear or taste food like 

we do and their behavior is instinctive. 

The eye is on the tip of the tentacles. The snail has two 

pairs of tentacles on its head. One pair is longer than the 

other pair. The eyes are on the longer pair. The shorter pair 

is used for smelling and feeling its way around. The 

tentacles are very important to a snail. 

Many gastropods are autonomous, meaning they can re - 

grow lost body parts. 

9

When the snail is disturbed, it simply withdraws or pulls its 

body back into its shell. The snail then seals the entrance 

with a mucus plug or a trap door, called an operculum. 

Many snails also use this trap door, to hold in valuable 

moisture during dry spells. This door is located on the top 

of their foot and when danger is around or they are required 

to maintain moisture, this operculum closes them into their 

shell. 

When land snails are threatened and want to hide, they go 

beneath leaves, stones or logs. 

The majority of snails are most active at night and on 

cloudy days. It does not like the sunshine very much. 

Snails do not like hot and dry conditions. They like it moist 

or humid and not too bright. 

During very cold weather or winter, it hibernates in the 

ground. During dry periods (droughts) molluscs also pull 

into their shells or create a mucus cocoon to keep in 

valuable moisture. This kind of hibernation is called 

aestivation. 

Snails have different shaped shells. It can be a single shell 

that is rounded or a pointed spiral or flat. They are often 

brightly coloured or some even have spines and ridges as 

well. 

A snail has fingernail file like tongue called a radula in its 

mouth for scraping food particles off. This radula is like a 

rough tongue-like ribbon, something like a file with rows 

of tiny teeth, which it uses to scrape off bits of leaves and 

flowers to eat. 

Snails eat mostly living plants as well as decaying plants. 

They also chew on fruits and young succulent plant barks. 

The snail moves by creeping or gliding along on a flat 

“foot” underneath its body. The band of muscles in the foot 

10

contracts and expands and this creates a kind of rippling 

movement that pushes the snail forward. The “foot” has a 

special gland that produces slimy mucus to make a slippery 

track. You can often see these silvery tracks in the garden. 

The slime comes out from the front and hardens when it 

comes into contact with air. The snail is able to move on 

very sharp pointed needles, knife, razors and vines without 

being injured because the mucus-like secretion helps to 

protect its body. 

The garden snail travels about 70 cm every 3 minutes-that’s 

1 km every three and a half days. 

Many snails are both male and female. Therefore, it can 

produce sperms and eggs at the same time! However, to 

fertilize the eggs, the snails need to exchange sperms with 

each other. An animal that is both a male and a female is 

called a hermaphrodite. This method of reproduction comes 

in very handy as these snails are very slow moving and 

don’t like moving around too much. If they had to go 

looking for a boyfriend or girlfriend, it could take them a 

very, very long time to have babies. 

The brown garden snail lays about 80 spherical shaped 

white or yellowish coloured eggs at a time into the topsoil 

of the ground. It can lay eggs up to six times a year. Snails 

take about 2 years to become adults. 

Snails have many natural enemies. They include ground 

beetles, snakes, toads, turtles, and birds, including 

chickens, ducks and geese. 

The largest known land snail is the Giant African Land 

Snail. It can weight up to 2lb (900g) and measure up to 

15.5 inches (39.3cm) from snout to tail. 

11

Many land snails are very strong: they can lift 10 times 

their own weight, even moving up the side of somethinglike 

a tree. 

Snails can live up to 10 years depending on which species 

you look at. Some have been known to live up to 15 years 

or longer. 

Many people get upset and farmers get angry when snails 

eat up their plants and crops. Snails can cause serious 

damage to crops. 

Many types of terrestrial snails such as the helicidae or 

escargot snails are actually farmed today. This farming 

method is called Heliciculture. 

Gastropods II: Aquatic (Pond or other Freshwater) 

snails: 

Fig. 2 :Pomacea bridgesi (Golden apple snail) 

The pond snail is, in many ways, like the garden snail. 

Pond snails are usually tan or dark brown in colour. 

Some pond snails have gills to breathe in water. Those with 

gills will live at the bottom of the pond. Those that do not 

have gills will come up to the surface to breathe and have 

pulmonary sacs which act like our lungs. These snails will 

12

live on the surface so that they can come up to breathe 

easily. 

You can often buy pond snails from a pet or aquarium 

stores. One common pond snail often sold is called 

“Apple” snail or golden snail. 

The pond snail feeds mainly on plants like algae and 

microscopic creatures that are found on the surface of 

waterweeds. They eat by scraping bits off with their rough, 

sandpaper-like tongue, just like the garden snails. 

When pond snails are threatened and want to hide, they 

bury in the sand, or hide beneath rocks or logs on the 

bottom of the pond. In the ocean, snails will hide in caves, 

or on rock ledges. 

Some snails have pointy spines on their shells to keep their 

enemies from eating them; some have very heavy shells 

that discourage their prey. Some snails have a body that 

comes over their shells to camouflage them from those that 

would eat them, and some are poisonous to fend off prey. 

Most pond snails reproduce just like the garden snail. It is a 

hermaphrodite. The only difference is that, unlike the 

garden snail, the pond snail carries its fertilized eggs with it 

or sticks them onto or under foliage or stones. If carried 

around on their mother’s shell, the baby snails will only 

leave their mother when they are hatched. 

Some pond snails can swim and others can bury themselves 

in the sand very quickly. 

Gastropods III: Marine Gastropods: 

These are the conchs (Strombidae), whelks (Buccinidae), 

limpets (Lotiidae), periwinkles (Littorinidae), cones 

(Conidae), volutes (Volutidae), and cowries (Cypraeidae) 

that live in the seas. 

13

Fig. 3 : Cypraea moneta (Money cowrie) 

Most seashells that people recognize and pick up along our 

beaches fit into this group of molluscs 

Most have a coiled shell. Their soft bodies have a head 

complete with two eyes located on the tops of two tentacles 

They have a big flat foot, which they use for locomotion 

and on the back end of this foot is a structure called an 

operculum, which acts as a trap door 

Most breathe through gills; however, some absorb oxygen 

from the water directly through a specialized membrane 

(something like the thin skin lining the insides of your 

cheeks) lining their mantle cavity. 

Many of these molluscs have very colorful bodies. Some 

members in this class only have a very small, fragile shell 

and it is often contained right inside their soft bodies or 

they may not have a shell at all. We know some of the 

Opisthobranchs as: sea hares, sea butterflies (Thecostoma), 

sea slugs (saccoglossans and nudibranchs), and canoe 

(Scaphandridae) and bubble shells (several families). 

All cone shells possess a poisonous dart (a modified radula) 

with which they harpoon, inject venom and thus kill their 

prey. Some cone shell possess venom is so toxic that if 

stung, it can severely harm or even be fatal to man. 

14

Many members of the Carrier shell family collect seashells. 

These shells scientists call Xenophoridae attach other shells 

or stones to their own shell for protection and camouflage. 

Sometimes they even use man-made objects such as glass 

and bottle caps! 

The largest snail (univalve) known attained a length of 78 

cm (two and one half feet) with a girth of nearly forty 

inches. This trumpet conch, Syrinx aruanus (Linneus, 

1758), weighed in at nearly forty pounds. 

The smallest known snail shell is the Ammonicera rota and 

measures only 0.02 inches in diameter. Fifty of them laid 

end to end would measure one inch! 

“Pelagic” gastropods live their entire life without ever 

touching bottom or shore! They float and travel on the 

ocean’s currents. The violet snail, the Janthina, can travel 

hundreds of miles in its lifetime as it floats around on the 

ocean’s currents. Its delicate shell only touches land when 

it gets washed up onto beaches during storms. 

Money cowries were the first item used by man for trade 

and a monetary system. Other examples of this are the 

wampum trade beads used by the North American Indian. 

Bivalves or Lamellibranchs : 

15

Fig. 4 : The Giant clam 

Covering their soft body is a thin membrane called the 

mantle (like a thick piece of skin). The mantle takes lime 

and calcium out of the water and turns it into a two piece 

shell 

Bivalves all have this two-part shell which is hinged 

together. These two shell parts are called valves. They open 

and close these valves by using strong adductor muscles 

and ligaments much like you bend your elbow or knee. 

They have a siphon (like a short, fat drinking straw that 

feels like rubber) which they use to pull in water and tiny 

animals that live in the water. They extract both oxygen 

and their nutrients from this inflow of water through gills 

which can filter out the tiny food particles from the water 

and pass them on to their stomach where they are digested. 

If a foreign object such as a piece of sand gets into their 

soft mantle, it hurts, so they take the same smooth shelly 

material that we put on the inside of their shell and cover 

the offending object up and make a pearl. 

16

Most bivalves reproduce by laying millions of eggs into the 

water surrounding us. The male bivalves then release their 

sperm into the same water. If the eggs and sperm meet, a 

new baby bivalve is born. However, some species hold 

their eggs in a space called the mantle cavity in their body. 

The males still spurt their sperm into the water and when 

she pulls this water in through her siphon, the eggs are 

fertilized. These are then brooded inside her body until she 

knows they are big enough to live in the water. She then 

releases them into the water. All juvenile bivalves start life 

as tiny specks, (larval stage) swimming in the water. When 

these larvae become big enough, they start to settle in their 

new homes. When they are still young, and settled, they are 

called “spat”. 

Some molluscs, such as the oysters, change sex. Some like 

oysters even alternate their gender. Male one year, female 

the next year, 

Some bivalves like to live attached to hard objects such as 

rocks or manmade objects. Some live all their lives buried 

beneath the sandy or muddy ocean, lake or stream bottoms. 

Some actually live inside wood. These bivalves (known as 

ship worms) have caused man a lot of trouble when he sails 

in wooden ships. for example the Barnacles make holes on 

the ship body. They also attack wharves and other wooden 

man made structures causing a lot of damages. Some of the 

other species are parasites, meaning that they live inside a 

living host. 

2. WHAT ARE ACTUALLY THE SNAILS? 

The scientific classification of snails shows that they 

17

elong to the Phylum Mollusca and Class Gastropoda 

(Curvier, 1795). The word snail is a common name that 

can be used for almost all members of this class. They 

are mainly characterized by having coiled shells in the 

adult stage (those snails which do not have a shell or 

only a very small shell are usually called slugs) Snails 

are second only to the insects in terms of total number 

of species. With more than 62,000 described living 

species, they comprise about 80% of living molluscs. 

Estimates of total extant species range from 40,000 to 

over 100,000, but there may be as many as 150,000 

species. There are about 13,000 named genera. 

Fig 4 : Anatomy of a Gastropod snail 

Apart from having extraordinarily diverse 

types of habitats, they vary extensively in form, habit, 

behaviour and anatomy. It has since been noted that among 

18

the snails, what is true of one species may not be at all true 

of another. They are found in the deserts, ditches and the 

abyssal depths of the sea. The great majority of snail 

species are marine, many are terrestrial and numerous can 

be found in the fresh water, and brackish water biomes. 

Many snails are herbivorous, though a few land species and 

many marine species are omnivores or predatory carnivores 

others are grazers, browsers, suspension feeders, 

scavengers, detritivores and there are suctorial forms. 

Snails are among the animal groups that everybody knows 

a little about. After rains, snails can be seen crawling 

around in bushes, trees, walls and roads at a proverbially 

slow pace and mainly at nights. Besides the characters 

typical for molluscs, there can also be found characters 

typical for all snails, whatever they may look like from 

outside. 

These common features include: 

(a) Foot: Most snails have got a noticeable muscular 

crawling foot with a flat sole. The animal uses it 

to move slowly but visibly. Besides this crawling 

motion, seen mostly among land, living snails, 

there are many alternative methods of locomotion. 

So many snails also are able to use their foot for 

digging. Among sea snails, there are species that 

can swim in the free water. In ponds and lakes 

there are arboreal snails that climb up and down 

trees, shrubs and herbs within the bodies of water 

19

(Azugo, 2009) and pulmonate forms swimming 

about in open water. 

(b) Head: At the end of the foot in the front end, a 

snail has its head. This head carries eyes and a 

variable number of tentacles. Most terrestrial 

snails are equipped with four tentacles; the 

remaining snail species only have two tentacles at 

their dispositions that may look like threads or 

look like ears. The eyes are attached on the tips or 

at the base of the tentacles. These positions are 

diagnostic 

(c) Operculum: At their foot’s rear end many water 

living snails (and few terrestrial species) carry a 

calcareous lid (operculum) that closes the shell 

aperture, when the snail withdraws. Using their 

“saber-shaped” conches, the snails are able not 

only to, defend themselves, but also to move in 

jumps by pushing their operculum into the ground 

and jerking themselves forwards. 

(d) Radula: Like other molluscs, snails feed with their 

rasp, tongue (radula). From the composition of their 

radula and the shape of their teeth, different snail 

groups may be distinguished, such as the primeval 

docoglossan beam tongue (limpets) or the 

carnivorous toxoglossan (meaning venom tongue of 

cone shells). The main function of the radula, 

whatever its appearance, based on the same 

20

principle, is a rasping tongue with tiny chitin teeth 

used for food provision. The number and shape of 

teeth is dependent on the type of nutrition, as it is 

among mammals (fig. 2). Herbivorous snails usually 

have many similarly shaped broad toothlets, that are 

connected to a venom gland and are used toinject the 

venom into its prey’s body as a snake. 

In grastropods, the jaw, radula and the reproductive 

tracts are useful in identification and systematic. The radula 

is a rasping structure consisting of a chitinous belt and rows 

of posteriorly curved teeth. This tongue like structure is 

supported by a cartilaginous odontophore and is situated on 

the floor of the buccal cavity. It lies on top of the 

odontophore. When the radula is projected out of the 

mouth, the teeth become erect. When the radula is retracted 

by muscles, the teeth scrape in algae. The radula teeth are 

worn with use. 

21

Fig. 

5: Radulae in the jaw of a snail 

(After Yoloye, 1988) 

(e) Shell: Snail’s shells mainly protect the snails 

backside (i.e. the visceral mass), but also several 

internal organs that are assembled in the dorsal 

visceral hump. The shell is produced by cells of 

the mantle, the tissue coat protecting the snail’s 

visceral hump and back. Originally snail shells 

differ noticeably from other mollusc shells, such as 

those of Nautilus, as they are asymmetrically 

coiled to one side of the body. 

Shell sculpture is a habitat dependent feature. Open 

surfaces (e.g. rocky plains swelling gastropods may be 

more exposed to shell crushing, predation particulary by 

fishes and rodents than sand dwelling species). This was 

part of the observation of Vermeil’s in 1978, that while the 

“most profound inter oceanic variations in architecture 

occur in open rocky surfaces”, changes in sand dwelling 

species are considerably less pronounced. Consequently 

22

sculptural defenses against crushing may be of greater 

importance to open surface dwelling species compared to 

sand dweller. 

For the lovers of beauty, shells of gastropods (fig. 6) have 

always offered a wide variety of opportunities for artistic 

ingenuity, producing many gift items. Some gastropods 

have striking colour patterns showing a good deal of 

contrasts. They may occur in the shell, foot, mantle or eys. 

Some are understandably camouflage and warning features 

and are distinctive for each species of one genus. Thus they 

are often used for species recognition. Most pulmonate 

gastropods have dull coloured shells without patterns. They 

have constellations in addition to their species specific 

micro-sculptures. 

Using molecular biological studies, it was found that the 

controls of colour patterns are located in several gene loci. 

It has been suggested that shell patterns are caused by 

deposition of shell pigments in the primitive molluscs. 

These pigments are believed to be derived from waste 

metabolic products removed from living tissues by 

incorporating them into shells. The fact that the substances 

are laid down in bands, spots, strips and other intricate 

patterns of constant nature indicates that the disposal of 

these wastes may definitely be under genetic control and so 

have adaptive value. 

Gastropod shells have three major layers – the inner or 

Ostracum, the middle which is relatively thick is the 

Calcareous while the outer or Periostracum is thin and 

transparent. The Periostracum is made of chitin like protein 

material called Concholin. This protein is secreted by the 

mantle. The Ostracum is also known as the nacreous layer 

23

and is formed from thin sheets of calzium carbonate 

alternating with organic matter. This nacreous layer is 

secreted by cells along the entire epithelial border of the 

mantle. Secretion of the nacreous causes the shell to grow 

in thickness. This thick shell helps in protecting the soft 

tissues of the gastropods. 

The snail shells have many shapes. The fundamental shape 

is globose while some are conical tubes; some are spirally 

coiled around a central axis – the columella. The separate 

coils of the spiral are called the whorls. Each whorl is 

partially covered by its successor. The line occurring where 

two whorls meet is called the suture. The last whorl is 

called the body whorl, and it is around the opening known 

as the aperture. 

24

Fig. 6: Shells of different freshwater snail species 

(After Thomas Kristensen, 2005) 

(f) Torsion: The Principal diagnostic criterion for the 

members of the class gastropoda is torsion. The 

25

. 

process of torsion was thought to be due to two 

different gradual adaptive processes: 

(a) To regulate stabilization of the larval 

equilibrium. 

(b) To regulate balancing posture in the plantigrade 

stage. The process of torsion therefore regulates 

differential growth processes e.g. shifting the 

mantle cavity into the anterior position. The 

mantle or shell sinus already existing appears to 

be a prerequisite for the survival of such torted 

animals in not shedding their waste products 

towards the inhalant currents. The regulative 

growth also includes the development of the 

right pallial organs and the right dorsoventral 

retractor muscle. 

The process of torsion and its consequences may be 

summarized thus: 

(a) The pretorsional presence of a planispirally 

coiled visceral hump with a mid posterior shell 

sinus or slit. 

(b) Regulative shifting of the leavy visceral mass of 

the larvae towards an arrangement of equilibrium 

for their balancing posture in the pelagic 

environment and the adaptive dominant 

development of the right larval dorsoventral 

retractor muscle. 

(c) Positively selective genetic stabilization of the 

precociously accelerated development of threat 

26

ight larval retractor i.e. establishment of the first 

phase of torsion (90%). 

(d) The predominant development of the 

pretorsional right (or the retarded development of 

the pretorsional left), pallial organs due to 

respiratory currents. 

(e) Regulation of the divergent axial and balanced 

conditions between the visceral hump and the 

head foot respective of plantigrade movement 

which is by differential growth processes in 

metamorphosing animals. That is the second 

phase of torsion of approximately another 90 o . 

(f) This regulation includes and is combined with 

the development of the second (post torsional 

right) set of pallial organs including the retractor 

muscle, the mantle or shell sinus or slit enabling 

the new paired inhalant respiratory current to be 

directed symmetrically from the latero-frontal 

areas towards the anterior-medio-dorsal area. 

In the larval stages of gastropods the internal organs 

undergo twisting as the animal develops. For example, the 

digestive tract is simply U-shaped but during torsion it 

completes a 150 o twist that brings the anus up over the 

mouth. This twist causes other organs on one side of the 

body to be compressed and fail to develop while the 

nervous system contorts to a figure eight. 

Among other groups after the torsion there is a counter 

clockwise detorsion, moving the pallial cavity to a position 

on the right side of the body, behind the heart. This 

situation can be found among the opisthobranchia (hind gill 

27

snails) and pulmonata (lung snails). In primeval snail 

groups the two main neural pathway run straight and 

parallel from front to back. After the torsion, in the 

prosobranch stage, those nerves are crossed, a situation 

referred to as chiastoneury. Those snail groups are also 

known as Streptoneura (crossed nerve snails). In contrary 

to that, after detorsion the nerves lie straight, and parallel 

again, which is why Opisthobranch and Pulmonate snails 

are grouped as euthyneura (straight nerve snails). 

(g) Systematics: 

There is controversy about the phylogenetic 

position of some gastropod groups. The 

relationship between the groups with each other 

remains unclear. The respiratory and neural 

systems of gastropods are used in the systematic 

arrangements of snail groups. Gastropoda is 

divided into: 

(a) Prosobranchia 

(b) Opisthotoranchia 

(c) Pulmonata 

Starting from the torsion process, two different adaptive 

phases in many orders of gastropods evolved. Recent 

gastropods appear to belong to different lines having 

achieved pallial symmetry independently thus: 

(i) The most conservative stock – also with respect 

to shell structure, possesses paired pallial organs 

and paired dorso ventral rectractor bundles in the 

adults. A common example is Haliotis. 

(ii) The predominance of the post torsional right 

rectractor muscle and helicoids coiling result in 

the loss of the left rectractor muscle. 

28

(iii) The hypertrophy of the right retractor muscle and 

helicoids coiling which leads to the suppression 

of the left retractor as well as to the right set of 

pallial organs e.g. Trochacea. 

(iv) The reason for the change in water currents and 

the abandonment of the right set of the pallial 

organs remains enigmatic. 

(v) The hypertrophy of the post torsional right 

excretory – genital duct causes the pronounced 

asymmetry with the loss of the right set of pallial 

organs e.g. Neritacea. 

(vi) The asymmetry of the pallial organs is due to a 

paedomorphous retention of the larval 

asymmetry prior to the regulation in the 

plantigrade stage. Owing to a long lasting 

planktotrophic larval life, the development of the 

right pallial organs as well as of the right 

retractor muscle was more and more retarded. 

The snail groups within the class gastropoda thus include 

snails, limpets, slugs, whelks, conchs, periwinkles, sea 

slugs, sea hares, sea butter flies, etc. These animal goups 

are basically bilaterally symmetrical. 

All the gastropods have common features i.e. the head, 

tentacles, and at some stage of their development they 

show torsion. 

(a) Prosobranchia (Milne-Edwards, 1848) are 

gastropods in which the adult shows torsion, the 

visceral loop is in figure 8 the gills are anterior to 

the heart. Common examples are Haliotis, 

Patella, Buccinium, etc. 

29

(b) Opisthobranchia are gastropods in which the 

adults show detorsion by a process of untwisting 

e.g. Aplysia, Doris, etc. 

(c) Pulmonata are gastropods in which the adult 

nervous system becomes symmetrically 

developed following torsion by a process of 

shortening of the abdominal commissures e.g. 

Achatina, Lymnaea Bulinus, 

Biomphalaria, etc. (see table 1) 

Table 1 : Comparative Study of the Morphology of 

the 3 Sub-Classes 

S/n Characters Prosobrachia Opisthobranchia Pulm 

1. Torsion The visceral mass 

exhibits torsion to 

a maximum 

degree 

2. Ctenidia Primitive forms 

have two gills. 

Advanced forms 

have one i.e. 

monopectinate 

3. Mantle Cavity The mantle cavity 

is anterior and 

hence the name 

Prosobranch. The 

opening is wide. 

Undergoes 

detorsion with 

Gut straight 

One or more or 

none secondary anal 

gills may be present 

When present 

cavity opens on the 

right side by a wide 

aperture 

30 

Com 

Gut 

Ctn 

The 

ante 

is n 

pneu 

roof 

and 

bein 

lung 

4. Auricles/Kidne Two auricles and One auricle and one One

ys two 

present 

kidneys 

5. Operculum Operculum 

present 

6. Nerves Figure 8 due to 

torsion 

7. Reproduction Sexes are 

separate free 

living veliger 

larvae is present 

h. THE CLASSIFICATION OF GASTROPODA 

Phylum Mollusca 

Class Gastropoda (Cavier, 1745) 

Sub class: Prosobranchia (Milne-Edwards, 1848) 

Order I: Archeogastropoda (Thiele, 1925) 

Sub order: Vetigastropoda nor 

Sub order: Decoglossa (Troschei, 1866) 

kidney present kidn 

No operculum No 

Straight 

detorsion 

due to 

Hermaphrodite 

veliger 

present 

larvae 

31 

Stra 

brai 

Her 

larg 

Dev 

dire

Sub order: Neritopsina (Cox, 1960) 

Order II: Caenogastropoda (Cox, 1960) 

Sub order: Mesogastropoda (Thiele, 1925) 

Sub order: Neogastropoda (Thiele, 1929) 

Sub class: Pulmonata (Cavier, 1817) 

Order: Archaeopulmonata (Morton, 1955) 

Order: Basommatophora (keterstein, 1864) 

Order: Stylommatophora (Schmidt, 1855) 

Sub class: Gymnomorpha (Slvini-Plawen, 1970) 

Order: Onchidiida (Rafinesque, 1815) 

Order: Soleolifera (Simrota, 1908) 

Order: Verohicellida (Gray, 1840) 

Order: Rhodopida (Fischer, 1883) 

Sub class: Opisthobranchia (Milne-Edwards, 1848) 

Order: Pyramidellimorpha (Freter, 1979) 

Order: Cephalaspidea (Fischer, 1883) 

Order: Anaspidea (Fischer, 1883) 

Order: Saccoglossa (Thering, 1876) 

Order: Ascoglossa (Bergh, 1879) 

Order: Notaspidea (Fischer, 1883) 

Order: Nudibranchia (Ducrotay-Blainerille, 

1814) 

Order: Anthobranchia (Ferussac, 1819) 

Difficulties exist when one wants to differentiate among 

gastropod species. Brown (1966) compared the copulatory 

32

organs of some species and found significant differences in 

the dimensions of the preputium and penis sheaths. Wright 

and Rollinson (1979) examined the possibility of using isoelectric 

focusing techniques in differentiating snail species 

and they found no clear enzyme type for certain characters. 

However these studies made enough in road to allow them 

suggest that biochemical taxonomic methods could be used 

to effectively differentiate the species. Jelnes (1979) using 

electrophoresis came to similar conclusions. Other methods 

that show promise are distribution of micro-sculpture on 

the shell, presence or absence of aperture bands, number of 

whorls, and characters of the radula. 

Biometric multivariate analyses of phenotypic characters; 

stepwise discriminant analysis of morphological characters 

of the shell and pairwise discriminant analyses are 

statistical tools that have been used in snail taxonomical 

studies. In these analyses, shape of shell, length of shell 

diagonal, width of shell at the level of the last suture, length 

of body whorl above the aperture and width of the shell are 

the factors that could be used to load the characters 

important in separating the Genera and species. 

i. ECOLOGY OF GASTROPODS 

Gastropods live in every conceivable habitat on earth. They 

are found in virtually all habitats ranging from high 

mountains to deserts, and to the rain forests. They are also 

found from the tropics to high altitudes. Many snails are 

benthic and mainly epifaunal, but some are planktonic. 

There are many microspecies of gastropods too numerous 

to count. 

It has also been found that the relationship between snails 

and plants are often mutualistic deriving a lot of benefits 

33

oth ways. The chemicals produced by plants often attract 

snails while the snails themselves develop strategies for 

locating and exploiting the plant species. It is now known 

that plants derive two major benefits from the snails eating 

them (especially dead plant materials) namely: 

(a) Removal of the dead tissues minimizes the risks of 

living tissues becoming invaded by pathogens. 

(b) The consumption of this material by snails increases 

the turnover rate of potentially growth limiting 

inorganic and organic nutrients for the plants. 

In further understanding the ecology of snails, the 

quantitative parameters which determine the interactions 

between the snails and the non living components of their 

environment are important to be known. These interactions 

determine the number of species available in the given 

habitat at any given time. 

Each species of snail in each habitat is known to be 

distributed according to the resource patterns in the 

environment. Thus each habitat has a theoretical maximum 

number of individuals that it can support a phenomenon 

referred to earlier as the carrying capacity of the habitat. 

The development and growth of gastropods are influenced 

by the environment in which they live. Various 

environmental cues, endocrine and neuroendocrine reponse 

mechanisms regulate the growth and reproduction in snails. 

These are known to be useful in snail farming where the 

goal is to optimize the production of edible snail species. 

a) Feeding: All snails are from one trophic levelprimary 

consumers that play important roles in the 

functioning of the ecosystems. Quantitative studies 

have shown that some activities of the snails are 

34

imperative for the ecosystem dynamics to operate 

smoothly (Mason, 1970). The food choices of snails 

are influenced by the qualitative composition of the 

foods, the qualitative availability and the nutritional 

needs of the snails (Calow, 1971). There is a 

positive correlation between food availability and its 

proportion in the diet (Okafor, 1990; Speiser, 2001). 

Diet itself has been found to vary seasonally and is 

shown to be specific to age (Baur, 1992). Snails 

feed on an assortment of plant and animal species 

including algae, bacteria, and fungi. They feed on 

whole plants and infusions as well as animal 

remains, food remains, while some are carnivorous, 

feeding on other animal species including other 

snails or their eggs. Snails are not everything 

selective and eat almost available in their 

environment. In general, they prefer soft and 

digestible vegetable. Tough plants and algae are 

consumed as long as they are able to grasp their 

pieces as food with their radula. They consume 

litters on the forest floors where they act as 

bioconverters that help recycle nutrients Studies 

show that the apple snails are mainly herbivorous 

but some exhibit cannibalistic behaviour e.g. 

Marisa conuarietis 

. Most snails are opportunistic feeders eating even fish, 

frogs, crustaceans and insects. They also cause 

deforestation in collection of food, this when superimposed 

on long pre reproductive periods, leads to low fecundity in 

gastropods (Egonmwan, 2004). 

35

a. DISTRIBUTION 

A major factor that affects the distribution of gastropods 

is the presence of calcium carbonate which the snails 

use to build their shells (Dennis, 1985), and for 

muscular movement. Most of the gastropods live on 

land, many live in the seas, others live in the freshwater 

and estuarine habitats. All are secretive in habit and 

hide under leaves, aquatic macrophytes and litters. They 

are active mainly during the night time and voraciously 

feed at this time. 

In many tropical parts of the world, many snails feed on 

lichens e.g. Bulimulus, some live on trees e.g. 

Orthalicus, and generally gastropods show a wide form 

of ubiquitous ness. Freshwater forms prefer to live in 

quiet water and among weeds and other aquatic 

macrophytes. Many prefer inhabiting swift flowing 

water and others enjoy living on stones and pebbles. 

The marine forms live in a wide assortment of 

microhabitats. Most are found hiding under rocks, in 

and around coral reef or on sandy substratum. A few of 

the marine snails live in the open sea. Wilbur (1933) 

showed that gastropods thrive mainly in the coastal 

zone of the marine habitat. Tropical waters have the 

richest diversity of gastropod species and in the warn 

waters, the most colourful species are found. Colder 

waters have fewer species. Most Marine snails are plant 

feeders, feeding on live vegetable matters and decaying 

plant tissues. A few are carnivorous and feed on other 

mollusks. 

The effects of some ecological factors on snail growth 

and distribution are difficult to assess as they may be 

36

oth of a direct and an indirect nature. Studies show that 

snails have distributional patterns in nature which 

strongly correlate with the distribution of specific 

aquatic macrophytes for freshwater species (Pimentel 

and white, 1959; Sturrock, 1974). It has also been found 

that the relationship between snails and plants are often 

mutualistic deriving a lot of benefits both ways. The 

chemicals produced by plants often attract snails while 

the snails themselves develop strategies for locating and 

exploiting the plant species. It is now known that plants 

derive two major benefits from being eaten by the 

snails (especially dead plant materials) namely: 

(i) Removal of the dead tissues minimizes the risks of 

living tissues becoming invaded by pathogens and 

damaged by toxins. 

(ii) The consumption of the material by snails increases 

the turnover rate of potentially growth limiting 

inorganic and organic nutrients for the plants. 












37

. REPRODUCTION: 

Most gastropod molluscs have separate sexes, 

but some groups are hermaphroditic. Most hermaphroditic 

forms do not normally engage in self-fertilization. Basal 

gastropods release their gametes into the water. Derived 

gastropods use a penis to copulate or exchange 

spermatophores and produce eggs. The egg matures and 

hatches into a trochophore larva that transforms into a 

veliger which later settles and undergoes metamorphosis to 

form a juvenile snail. 

The development and growth of gastropods are influenced 

by the environment in which they live. Various 

environmental cues, endocrine and neuroendocrine 

response mechanisms, regulate the growth and 

reproduction in snails. These are known to be useful in 

snail farming where the goal is to optimize the production 

of edible snail species. Some of the factors that affect 

growth and reproduction are light, photoperiod, and 

temperature. Photoperiod specifically affects egg- laying. It 

is observed that snails receiving 9h of light per day, do not 

lay eggs while reproductively active snails continue to lay 

eggs when transferred from the field to controlled long-day 

environment (L:D 18:6). Exposure of similar snails to 

short- day period regime (8 h / day) caused a depression in 

spermatogenesis. Changes in temperature have similar 

effects on gametogenesis. 

The role of endocrine secretions has been well elucidated. 

Distinct neurosecretory cell types, found in the nerve 

ganglia acting with steroids in the ovotestis help to 

metabolize androsteredione and synthesize steroid 

hormones like ecdysteroids that accelerate the production 

of spermatozoa in males or stimulate oogenesis in the 

38

females.. Self fertilization is a common mode of 

reproduction and mating is often absent while ovposition 

results from the transfer of stimulatory substances with 

origin in the reproductive tract during mating. Snails are 

hermaphrodites. Although they have both male and female 

reproductive organs, they must mate with another snail of 

the same species before they lay eggs. Some snails may act 

as males one season and as females the next. Other snails 

play both roles at once and fertilize each other 

simultaneously. When the snail is large enough and 

matures enough, which may take several years, mating 

occurs in the late spring or early summer after several 

hours of courtship. Sometimes there is a second mating in 

summer. In tropical climates, mating may occur several 

times a year. In some climates, snails mate around October 

and may mate a second time 2 weeks later. After mating, 

the snails can store sperm received for up to a year, but it 

usually lays eggs within a few weeks. Snails are sometimes 

uninterested in mating with another snail of the same 

species that originated from a considerably distant place. 

For example, some H. aspersa from southern France may 

reject H. aspersa from northern France. 

Snails need soil at least 2 inches deep in which to lay their 

eggs. For H. pomatia, the soil should be at least 3 inches 

deep. Keep out pests such as ants, earwigs, millipedes, etc. 

Dry soil is not suitable for the preparation of a nest, nor is 

soil that is too heavy. In clay soil that becomes hard, 

reproduction rates may decrease because the snails are 

unable to bury their eggs and the hatchlings have difficulty 

emerging from the nest. Hatchability of eggs depends on 

soil temperature, soil humidity, soil composition, etc. Soil 

39

consisting of 20% to 40% organic material is good. 

Maintaining the soil moisture at 80% is optimal. 

Researchers remove eggs immediately after they are 

deposited, for counting, then keep them on moist cotton 

until the eggs hatch and the young start to eat. Snails lose 

substantial weight by laying eggs. Some do not recover. 

About one-third of the snails will die after the breeding 

season. 

Snail eggs measure from about 3 - 5mm in diameter and 

have a calcareous shell with high yolk content. The eggs 

are laid in holes dug out in the ground. (Data varies widely 

on how long after mating snails lay eggs.) The snail puts its 

head into the hole or may crawl in until only the top of the 

shell is visible; then it deposits eggs from the genital 

opening just behind the head. It takes the snail 1 to 2 days 

to lay 30 to 50 eggs. Occasionally, the snail will lay about a 

dozen more a few weeks later. The snail covers the hole 

with a mixture of the slime it excretes and dirt. The slime, 

which the snail excretes is to help it crawl and to help 

preserve the moisture in its soft body. It is a glycoprotein 

similar to egg white. 

Fully-developed juvenile snails hatch about 3 to 4 weeks 

after the eggs are laid, depending on temperature and 

humidity. Birds, insects, mice, toads and other predators 

take a heavy toll on the young snails. The snails eat and 

grow until the weather turns cold. They then dig a deep 

hole, sometimes as deep as 1 foot, and seal themselves 

inside their shell and hibernate for the winter. This is a 

response to both decreasing temperature and shorter hours 

of daylight. When the ground warms up in spring, the snail 

40

emerges and goes on a binge of replacing lost moisture and 

eating. 

H. aspersa egg is white, spherical, about 3mm in diameter 

and is laid 5 days to 3 weeks after mating. (Data varies 

widely due to differences in climate and regional variations 

in the snails’ habitats.) H. aspersa lays an average of 85 

eggs in a nest that is 1- to 1 ½-inches deep. Data varies 

from 30 to over 120 eggs, but high figures may be from 

when more than one snail lays eggs in the same nest. 

In warm, damp climates, these snails lay eggs as often as, 

once a month from February through October. This 

depends on the weather. Mating and egg-laying begin when 

there are at least 8 hours of daylight and continue until days 

begin to get shorter. In the United States, longer hours of 

sunlight that occur when temperatures are still too cold will 

affect this schedule, but increasing hours of daylight still 

stimulate egg laying. If warm enough, the eggs hatch in 

about 2 weeks, or in 4 weeks if cooler. It takes the baby 

snails several more days to break out of the sealed nest and 

climb to the surface. Snails mature in about 2 years. In 

central Italy, H. aspersa hatches and emerges from the soil 

almost exclusively in the autumn. If well fed, and not 

overcrowded, those snails that hatch at the start of the 

season will reach adult size. They form a lip at the edge of 

their shell by the following June. If you manipulate the 

environment to get more early hatchlings, the size and 

number of snails that mature the following year will 

increase. In South Africa, some H. aspersa mature in 10 

months, and under ideal conditions in a laboratory, some 

have matured in 6 to 8 months. Most of H. aspersa’s 

41

eproductive activity takes place in the second year of its 

life. 

By contrast, one giant African snail, Achatina achatina, 

lays 100 to 400 elliptical eggs that each measure about 

5mm long. Each snail may lay several batches of eggs each 

year, usually in the wet season. They may lay eggs in holes 

in the ground like H. pomatia, or lay eggs on the surface of 

a rocky soil, in organic matter, or at the base of plants. In 

10 to 30 days, the eggs hatch releasing snails about 4mm 

long. These snails grow up to 10mm per month. After 6 

months, the Achatina achatina is about 35mm long and 

may already be sexually mature. Sexual maturity takes 6 to 

16 months, depending on weather and the availability of 

calcium. This snail lives 5 or 6 years, sometimes as many 

as 9 years. 

Some of the factors that affect growth and reproduction are 

light, photoperiod, and temperature. Photoperiod 

specifically affects egg laying. It is observed that snails 

receiving 9h of light per day, do not lay eggs while 

reproductively active snails continue to lay eggs when 

transferred from the field to controlled long-day 

environment (L:D 18:6). Exposure of similar snails to 

short- day period regime (8 h / day) caused a depression in 

spermatogenesis. Changes in temperature have similar 

effects on gametogenesis. 

The role of endocrine secretions has been well elucidated. 

Distinct neurosecretory cell types, found in the nerve 

ganglia acting with steroids in the ovotestis help to 

metabolize androsteredione and synthesize steroid 

hormones like ecdysteroids that accelerate the production 

42

of spermatozoa in males or stimulate oogenesis in the 

females.. Self fertilization is a common mode of 

reproduction and mating is often absent while oviposition 

results from the transfer of stimulatory substances with 

origin in the reproductive tract during mating. 

c. VARIOUS FACTORS AFFECTING 

SNAIL DISTRIBUTION 

Factors affecting the distribution of gastropods 

include the nature of the substratum, certain physical, 

chemical and biological factors. Other factors include: 

mortality, diversity, turnover, disturbance, and 

productivity. It has been observed that the snails’ 

responses to these factors are species specific and each 

species is able to maintain their populations within 

certain limits of tolerance. 

A habitat can sustain a certain maximum number of 

individuals (the carrying capacity) which is determined 

by the availability of resources e.g. food quality, as well 

as space. The density of species living in a relatively 

stable environment fluctuates around the unstable 

environments and may never approach the carrying 

capacity, they fluctuate severely. In unstable 

environment there is regular high mortality caused by 

the periodic unfavourable conditions. 

The effects of some ecological factors on snail growth 

and distribution are difficult to assess as they may be 

both of a direct and an indirect nature. Studies show that 

snails have distributional patterns in nature which 

strongly correlate with the distribution of specific 

aquatic macrophytes for freshwater species (Pimentel 

43

and white, 1959; Sturrock, 1974). It has also been found 

that the relationship between snails and plants are often 

mutualistic deriving a lot of benefits both ways. The 

chemicals produced by plants often attract snails while 

the snails themselves develop strategies for locating and 

exploiting the plant species. It is now known that plants 

derive two major benefits from the snails eating them 

(especially dead plant materials) namely: 

(a) Removal of the dead tissues minimizes the 

risks of living tissues becoming invaded by 

pathogens. 

(b) The consumption of this material by snails 

increases the turnover rate of potentially 

growth limiting inorganic and organic 

nutrients for the plants. 












44

d. LIFE CYCLE & LIFE BUDGET SUDIES: 

Other important things involved in the ecology of snails 

include growth rates, key factor analyses, capacity for 

increase, net reproductive rate that constitute Life Budget 

studies. Iheagwam and Okafor (1984) collected long term 

data on the numerical and production changes in Bulinus 

globosus and Lymnaea natalensis (gastropods). They 

followed the population dynamics and production of many 

consecutive cohorts of the snails and found roles for 

density and habitat quality in controlling reproductive rates 

in the gastropods. They concluded that horizontal (cohort) 

life tables were statistically acceptable in such studies and 

encouraged its use in the study of other species of 

gaqstropods. 

To calculate cohort production, the life cycles are often 

divided into time intervals while for production in the 

snails it will be subdivided into age intervals. Such life 

tables are prepared by following the survival of consecutive 

cohorts of snails over their life span. Egg production 

estimates are used to calculate the net reproductive rates 

(RO). From such life tables information on age specific 

survivorship rates (LX), age specific fecundity rates (MX) 

and mortality rates(qx) are also obtained for each species. 

Analysis of the brood years performances usually show a 

positive linear correlation. The degree of linearity of the 

data collected often suggests how the carrying capacity of 

the habitat is declining. 

Survivorship data suggest the type of regulation of the 

brood size which in itself narrows the number of survivors 

at maturity. The survival pattern when integrated with the 

reproductive rates often assesses the success or failure of 

45

each brood in replacing its initial numbers during its 

reproductive span in a given population. 

Various studies on the ecology of gastropods threw up the 

conclusion that snails in nature suffer heavy mortality 

during production even though that the ROs suggest 

tremendous production potentials. The mean generation 

LxMx 

time (T) calculated as T = å shows how long 

Ro 

the snails are expected to live while the age specific 

mortality rate (qx) can also be derived using the data. 

Okafor (1990a) showed that seasonal fluctuations occur in 

snail density and this correlates positively with the rhythm 

of rainfall. Further, Anya and Okafor (1990a) added that 

topographical water types affected snail ecology 

tremendously. Another fact revealed was that conditions 

prevailing during the early dry seasons are more favourable 

to the snails than those prevailing during the late rainy 

season. 

In other similar studies, Anya and Okafor (1990b) 

suggested that snail abundance depended on such 

environmental factors as temperature, altitude, current 

speed, turbidity, shading and nature of the substratum. 

Okafor in 1984 had suggested that there was high positive 

correlation between P H , Calcium ions, Magnesium ions, 

and snail abundance. Anya and Okafor (1991) showed a 

negative correlation between humic acid and snail 

abundance, distribution and density. From all those later 

studies we gather that the snails have a wide tolerance 

range for many of the factors and that the interactions of 

these factors also result in definite community structuring 

for the snails. Thus most of the snail communities were 

46

competitively loosely packed. With this form of 

distribution, the relative abundance follows the distribution 

of resources, with each species occupying its fundamental 

niche. In real life, within species rich communities, the 

average niche width and niche overlap declines. 

The snails are mostly hermaphroditic in nature, this allows 

for self fertilization and parthenogenesis, Aphallic species 

often occur from African species. Snails also survive in the 

environment because of the nature of their shells. 

5. IMPORTANT ROLES OF SNAILS IN HUMAN 

AFFAIRS 

(a) EFFECTS OF SNAILS ON THE ECOSYSTEM: 

(h) Feeding: All snails are from one trophic levelprimary 

consumers that play important roles in 

the functioning of the ecosystems. Quantitative 

studies have shown that some activities of the 

snails are imperative for the ecosystem dynamics 

to operate smoothly (Mason, 1970). The food 

choices of snails are influenced by the qualitative 

composition of the foods, the qualitative 

availability and the nutritional needs of the snails 

(Callow, 1971). There is a positive correlation 

between food availability and its proportion in 

the diet (Okafor, 1990). Diet itself has been 

found to vary seasonally and is shown to be 

specific to age (Baur, 1992). Snails feed on an 

assortment of plant and animal species including 

algae, bacteria, and fungi. They feed on whole 

47

plants and infusions as well as animal remains, 

food remains, while some are carnivorous, 

feeding on other animal species including other 

snails or their eggs. Snails are not selective and 

eat almost everything available in their 

environment. In general, they prefer soft and 

digestible vegetable. Tough plants and algae are 

consumed as long as they are able to grasp their 

pieces as food with their radula. They consume 

litters on the forest floors where they act as 

bioconverters that help recycle nutrients Studies 

show that the apple snails are mainly herbivorous 

but some exhibit cannibalistic behaviour e.g. 

Marisa conuarietis 

Two techniques are used to devour other snails: attacking 

the prey by introducing the proboscis into the aperture of 

the victim and eating the flesh or by gnawing holes into the 

victim’s shell in several stages with the radula and eating 

the exposed tissues. Most snails are opportunistic feeding 

on even fish, frogs, crustaceans and insects. Deforestation 

and collection for food, superimposed on long pre 

reproductive periods lead to low fecundity (Egonmwan, 

2004). 

Snails therefore feed on an assortment of plant and animal 

species including algae, bacteria, and fungi. They feed on 

whole plants and infusions as well as animal remains, food 

remains, while some are carnivorous, feeding on other 

animal species including other snails or their eggs. Snails 

are not selective and eat almost everything available in 

their environment. In general, they prefer soft and 

48

digestible vegetable. Tough plants and algae are consumed 

as long as they are able to grasp their pieces as food with 

their radula. They consume litters on the forest floors. 

Carnivory in some Taxa involve grazing on colonial 

animals. Some others engage in hunting their preys. 

Two techniques used in devouring other snails include 

attacking the prey by introducing the proboscis into the 

aperture of the victim and eating the flesh; or by gnawing 

holes into the victim’s shell in several stages with the 

radula and eating the exposed tissues. Most snails are 

opportunistic, feeding on even fish, frogs, crustaceans and 

insects. 

(i) Predators: Snails are a popular food source for 

various animals like birds, turtles, tortoise, 

fishes, insects, crocodiles, snakes, snail kites, and 

lizards. Mammals including man also prey upon 

snails. Table 2 gives a list of some groups 

identified as predators of snails. 

TABLE 2: LIST OF SNAIL PREDATORS 

Names of the predators of their types 

Insects Sciomyzidae 

49

Odonata 

Water bugs 

Lampyridae (fire flies) 

Hydiophillidae 

Solenopsis sp 

Ground beetles 

Leeches 

Decollate snails 

Predatory 

caterpillars(Hyposmoso 

ma malluscivora), 

Eciton, etc 

Ochromusca sp 

Fishes H 

Amphibians Rana pipiens 

Various salamanders 

Crocodilians Alligator 

Crocodylus 

Paleosuchus sp 

Caimau sp 

Reptilia Snakes 

lizards 

Flat Worm Leucochloridium 

paradoxum 

Crayfishes Procambarus sp 

Crustaceans 

Mammals Rice rats 

Water rats 

House rats 

Other mammals 

50

Birds Various ducks 

Storks 

Kites 

Other birds. 

(iii) Nutrient recycling 

From this stand point, snails play important roles in the 

recycling of materials from the producers to the consumers’ 

levels of the food chain in an ecosystem. Due to their litter 

feeding habits they recycle minerals from plant tissues to 

the soil thus improving soil fertility. 

Snails are endowed with a lot of enzymes including 

cellulases which allows them to play a major role in 

primary decomposition of plant materials. The 

mucoproteins in snail faeces and slime are useful in binding 

soil particles thus according to Newell (1967) they help in 

the development of crumb structure of the soils. 

The burrowing activities of snails like those of annelids 

permit easy air movement inside the soil. Malek (1982) 

stated that the presence of food increases the biotic 

potential of snails in that more eggs are laid whole maturity 

attainment is rapid with a gross enhancement of growth. He 

also showed that snails help pollute their habitats by 

dumping waste materials, by the accumulation of large 

quantities of organic materials of vegetables or animal 

origin. They also dump industrial wastes into the habitats. 

It has been reported that cases of helicine snail poisoning 

have been found in man when noxious content of the snail 

alimentary tracts were not removed before the snails are 

51

cooked. Such wastes contain large granules of oil, acids, 

mineral contents, and poisonous wastes all of which also 

reduce the snail populations when their levels exceed the 

tolerance limit. 

(iv) Factors affecting snail populations 

Four environmental factors affect snail populations 

viz 

Water levels. 

Current speed 

Temperature/shades 

Elevation. 

(b) Snails as Biological Indicators of Pollution and age 

of the environment: 

Palaeoecologists have since noted the presence of 

gastropod remains in geological sediments and included 

these in the interpretation of geological age of past 

environment and perturbations (Crisman, 1978). The 

shells of gastropods are preserved well and are located 

in calcareous sediments. These fossils provide 

information regarding water and soil chemistry, lake 

trophic state, variations in oxygen distribution and 

concentrations over time, and the changes in water 

levels following geological times. 

Studies show that molluscs generally do not inhabit 

strong acidic waters and their shells are rarely preserved 

in weakly acidic environments. In freshwaters Okafor 

(1990) traced the relationship between humic acids and 

snail distribution and abundance and found a highly 

negative correlation. In that study, it was observed that 

52

when mineral ions form chelate complexes with humic 

acids, snails begin to establish in such habitats. Studies 

with sedimentary core sampling for molluscan analysis 

have been used to identify areas that were the lower 

limits of littoral zones in the past geologic times. The 

value of snails in applied palaeoecology has been 

further demonstrated by using carbon dating 

technologies. The pulmonate snails which breathe 

atmospheric oxygen were found to be completely 

replaced by clams and prosobranch snails as a result of 

eutrophication of their aquatic environment. This was 

the first indication of the possibility of using snails as 

valuable palaeoindicators of human impacts on aquatic 

systems. 

Soils normally contain at least trace quantities of the 

heavy metals e.g. copper, lead, zinc, Nickels, Cadmium 

and mercury. In some areas, levels of these metals have 

been substantially increased from mining waste tips 

from industrial fallouts e.g. from smelting industries or 

by lead derived from car exhausts and by the use of non 

biodegradable pesticides (i.e. insecticides, herbicides 

and molluscicides). Snails are often used to monitor the 

concentrations of these metals because when they reach 

certain levels in the environment they become toxic to 

plants and animals including snails. Cavalloro and 

Ravora (1966) suggested that the gastropods are good 

biological indicators of manganese contamination in 

terrestrial environments. A study of the concentration of 

nine metals in the tissues of A. ater from locations close 

to, or far away from highways in Canada by Rophazard 

D’auria (1980) made them to suggest that these 

molluscs, might be useful as bio monitors for assessing 

53

environmental quality. These gastropods were 

particularly suitable as they are widely distributed in 

rural and urban environments. They tend to have 

specific home ranges and habitat preferences 

The distribution of metals in the tissues of these slugs 

collected from relatively unpolluted sites and those 

collected from sites near disused lead and zinc mines 

where manganese levels are so high were compared 

(Irland, 1979). The comparison showed that all metals, 

except manganese were higher in tissue concentrations 

in the slugs found in the polluted areas when the 

concentrations in the mollusks where compared with 

situation in other invertebrates, it was found that 

molluscs accumulated higher concentrations of mental 

ions than other groups of invertebrates. Marigomez et 

al; (1986) however observed that the higher 

concentrations of these metals in the tissues did not 

translate to higher mortalities thus making the molluscs 

potential bioindicator tools for the environmental 

pollutions with metals Greville and Morgan (1990) 

reached similar conclusion and stated that the intrinsic 

variability in metal levels increase the likelihood of 

using gastropods as biological monitors of metal 

contamination in terrestrial environment. 

Hydrogen sulphide and methage are produced during 

anaerobic bacterial decomposition and when these 

substances come into contact with the upper oxygenated 

layers, they produce deleterious effects on snail. 

Similarly, high concentrations of zinc, copper, cadmium 

or lead ions, are highly toxic to snails at levels above 

1.0ppm. At intermediate levels (0.05 – 1.0ppm), they 

54

produce stress. Thus snail distribution and abundance 

should indicate the presence or absence of these 

pollutants in the environment. Having this knowledge 

helps in protecting human health since most of the 

environmental pollutants constitute serious public 

health hazards. 

(b) SNAILS AS HUMAN FOOD: 

Domestication of wild species has been particularly 

popular in the West African sub-region where 

“bushmeat” is a most important dietary item. The giant 

African land snails have been variously studied, 

especially in Ghana and Nigeria as they are avidly 

consumed. Studies on the various aspects of biology 

and ecology as well as capture rearing of the snails have 

been going on in the Department of Zoology of the 

University of Ghana for over 25 years (Hodasi, 1973). 

These snails have been found to provide alternative 

sources of animal protein complementing that from 

other foods. 

The edible giant snails in Africa belong to two genera: 

Achatina (Lamarch) and Archachatina (Albers). Species 

of both genera are common south of the Sahara. 

Achatina achatina is the most common species in West 

Africa whereas Archachatina marginata occurs more in 

Southern Nigeria and in the Congo basin (Hodasi, 

1984). The snails are collected in large numbers by 

rural people and are marketed fresh or smoke dried. 

During the rainy season, the snails are cheap and 

abundant. 

In 1961, Mead reported from the 1919 paper of one 

Scientist called Lang that the snails were avidly 

55

consumed in. Belgian Congo and that Japanese roasted 

their snails and consumed them with Soya sauce. This is 

in addition to several reports of the use of snails as food 

in Europe, South America and other parts of Africa. Our 

bodies require a constant supply of energy and raw 

materials to maintain vital functions and to rebuild 

tissues worn out in the day to day processes of living. 

Snails may not be an energy giving food item but it is 

surely a mineral and protein giving food supplement. It 

is common knowledge that in addition to calories, we 

need specific nutrients in our diet, such as proteins, 

vitamins, and minerals. People in richer countries often 

eat two much meat, salt and fat and too little fibre, 

vitamins, trace minerals and other components lost from 

highly processed foods. In poorer countries, people 

often lack specific nutrients because they cannot afford 

more expensive foods such as meat, fruits, and 

vegetables that would provide a balanced diet. It is in 

these latter situations that snail consumption plays very 

important roles in mineral and protein supplementation. 

The nutrient composition of raw snails (per 100 grams of 

edible portion), according to information from the 

proximate analyses of snail meat is: 

Energy (kcal): 80.5 

Water (g): 79 

56

Protein (g): 16 

Availablecarbohydrates(g): 2 

Fibres (g): 0 

Fat (g): 1 

Magnesium (mg): 250 

Calcium (mg): 170 

Iron (mg): 3.5 

Vitamin C (mg): 0 

Improved nutrition and food sufficiency are two of the 

main priorities in providing food and nutritious products. 

Several studies have shown that the protein content of snail 

meat is higher than in livestock and guly slightly less than 

in poultry and giant rats. The fat content of snail meat is 

much lower than in Mammalian or poultry flesh. Snail 

meat is rich in calcium with an exceptionally high content 

of iron (measuring up to 12.2mg/100g). The energy content 

of snail meat is about 80k/cal/100g. it also contains high 

levels of phosphorus while being low in sodium and 

cholesterol. 

In France, it has been suggested that snails be used instead 

of precious beef in animal feeds and in preparing 

57

acteriological culture plates. As far back as 1944, a 

nutritionist known as Aguayo asked people to return to the 

consumption of snails. In the United States of America, 

records show that Helix pisana (Theba) were being sent 

from Sicily for consumption and a report from the U.S. 

Bureau of Entomology and plant Quarantine revealed that 

about 721 cases and 24, 969 baskets of living snails were 

once imported into New York between May, 1947 and 

April, 1948 (Mead, 1951). 

Further reports suggested that for a number of years, almost 

exactly one million pounds of snails were imported 

annually into the U.S.A. just from Morocco (Heifer, 1949). 

With approximately fifty snails to the pound the total 

number of snails would be close to 50 million or in linear 

measurement, close to a thousand miles of snails placed 

head to tail. 

Who would have guessed that such an appetite for snails 

existed just in U.S.A. Human use of land snails as food 

ranges from Native Americans consumption of Oreohelix 

sp in the Western States to fine dining escargots (Helix spp) 

in urban areas. For France (another country where snails 

are avidly consumed) the amount of snails eaten surpass the 

U.S. figures by about fifteen times or greater. 

In West Africa, especially in Ghana, various species of 

snails especially the Tiger snails are eaten. There the snails 

actually form the largest single item of animal protein in 

the diet of the common people. It was in that country that 

people can eat snails after boiling in water or on hot coals, 

removing the shell, freed of the soft visceral mass, 

chopped, and combined with starchy dishes such as cassava 

58

or cocoyam, and palm oil or pea nut oil to form their 

standard meal of fufu. 

In Nigeria, snails are eaten as food especially in the rain 

forest belt. The nutritive value of one species of snails 

eaten in Nigeria (Achatina) was found to correlate with 

what was already known for snail meat. For example, 

Wilson et al, (1975) showed that protein is a major 

component of snail body, exceeded only by water thus snail 

meat was advocated for use in Kwashiokor cases. Due to 

the iron contents, snail meat is often recommended in cases 

of anaemia. Quantitative measurements put protein in snail 

meat at 57.08 ± 5.99% per g dry wt. Russel – Hunter 

(1968) while analyzing the meat from either Achatina or 

Helix put the protein value at 85.5%. He found that there is 

an abundance of fat soluble vitamins (Vit. A, D, E and K). 

Also found are Linoleic acid, Linolenic acid and 

Arachidonic acid all essential fatty acids (Ajayi, et al., 

1974). Snails are also found to contain a lot of Lecithins. 

Probably because of these nutritive facts, snails are eaten in 

large numbers in Italy, South America, Malaya, Thailand, 

Japan, Africa and China. 

From the foregoing it seems that many agree that snail is 

rich in nourishment, good as a tonic and will give excellent 

dishes in vinegar mixtures, sesame bean mash, bean mash 

mixture, broiled with soy, coquille or stew. 

EDIBLE SNAILS 

My work had exposed me to many aquatic and terrestrial 

snails and edible species can be found in both 

environments. Such snails are widely distributed among the 

various genera and in many parts of the world. Snails are 

59

noted to be in the wild and are gathered by the very poor 

(especially women and children) from eating, and also for 

sale to urban dwellers. The afrotropical region of the world 

(housing the sub-Saharan Africa) harbours the largest 

number of land snails that are consumed by man and also 

the biggest known carnivores among the land snails 

(Watelina cafra, Rhytididae). Archachatina marginata is 

the largest land snails in the world and is a widely sought 

after species due to the size, distinct makings and lack of 

availability. They are more difficult to breed than other 

African snails. 

They are found in the dense forest floors in the forest zones 

of West Africa. They are believed to have a 3 year breeding 

cycle which is longer than other snails. This fact, coupled 

with deforestation and snail picking for consumption has 

caused the numbers to dramatically fall over the last 20 

years. Unfortunately, they are considered to be the most 

prized snail for eating followed by Achatina achatina and 

Achatina fulica. 

This region (Afrotropical) has also the richest and most 

diverse terrestrial malacofauna. Some species of land snails 

were already known as early as 1758 as Linnaeus in his 

basic work validly described Achatina achatina S.n., Bulla 

achatina (an East American species). The knowledge of 

land snails of the African continent was first summarized 

for South Africa. Latter those of Angola were reported with 

those of East Africa by Beurguinat by 1889 and Von 

Martens in 1897 for N.E. Africa by Jickeli in 1874. In 

Central Africa, specifically in Camerouns the reports of 

Aclly in 1896 other sin the 20 th century include Kobelt for 

N.E. Africa in 1909; in South West Africa, Connolly in 

60

1925, 1931, at Angola and Namibia; Connolly and Degner, 

in 1934, worked in West Africa on Edible Land Snail. In 

Nigeria, Ajayi et al (1974); Akinnusi (1998), Hodasi (1973, 

1982), Imevbore and Ajayi (1988), Okafor (1990, 2001) 

did intensive work on the biology, ecology and production 

of both land and freshwater snails. 

The total number of land snails in Africa is estimated to be 

about 6000 and these were found to belong to about 34 

families. Of these about 189 genera are fully identified; 

80% of these are recognized as endemic to the continent. 

However, it is known that of all these only 3 families 

dominate and have their endemic genera all over Africa. 

These include, Subulinidae, Achatinidae and Urocyclidae. 

The Achatinidae have about 23 genera of which 9 or 39% 

are endemic to West Africa. For the other 2 families, 

Subulinidae contains 21 genera with 6 or 18% are endemic 

to Africa. The zoogeographical analysis of land snails 

species isolated four areas of endemism in Africa namely; 

(a) Southern Africa 

(b) Northeast Africa 

(c) Eastern Africa 

(d) Central and West Africa (See table below). 

The central and West African zone represents the largest 

continuous forest refugium in Sub-Saharan Africa. This 

area has the greatest numbers recorded in Cameroun and 

Gabon. These two countries still represent the single most 

important area in Africa in terms of diversity of land 

mollusks. There are other three minor forest refugia 

namely: 

(a) Niger Delta (in Nigeria) 

(b) In Ghana and Ivory Coast 

61

(c) In Liberia and other parts of the tropical 

rainforest, and the Guinea Savannah, forest 

mosaic in Nigeria. 

The population of edible land snails is high in the wild and 

because the people of Africa are beset with acute protein 

shortages many people tend to eat a lot of snails to assuage 

the acute shortage. The known nutritive value of the snails 

makes it unthinkable not to harness it for human benefits in 

view of the acute shortages. In most areas, the land snails 

and some aquatic forms (e.g. the prosobranchs) are 

collected indiscriminately by the rural people for their 

family consumption on a daily basis. However some collect 

them to sell in the local markets from where they find their 

way to the urban markets. Our studies show that edible 

snails are also consumed in Europe and North America. 

In these places the snails are sold in shops and restaurants. 

The traditional European species of what they call 

“Escargots” is relatively small and slow at growing, so the 

demand for snail meat which has tremendously grown over 

the years has been partially satisfied by importation of the 

fleshy giant African land snails, “Escargot achatine”. 

The commercial success of farm ranching Escargot 

achatine may be appreciated by the observation that as far 

back as 1977, over 1,500 tons of canned snail meat, worth 

US $3 million was shipped into Europe from Taiwan alone. 

The giant African substitutes are said to be slightly inferior 

in quality to the European edible snails because it is 

“rubbery” and too often have “swampy-tastes”. This 

quality disadvantage is usually addressed by flavouring the 

62

meat with garlic. British species are also well accepted as 

meat in most countries. 

It is now known that edible snails can be farmed using 

different pen systems, Cages and Tanks. The snails have 

high biotic potentials and large net reproductive rates (Ro) 

and so have the capacity to thrive well in captivity. The can 

feed on a large variety of readily available plant food 

materials. It has been proven that rearing the snails in 

captivity helps in sustainable supply of snail meat to meet 

the increasing demand for snail meat and in conserving 

these animals. The adult grow up to 200mm and weigh 

about 250g. 

THE KNOWN EDIBLE SNAIL SPECIES 

In Africa and Europe, the following are edible snails. 

Besides the species listed there are many more species in 

many countries of the world. 

Table: 3: List of Land Snail Families from 

Africa 

S/No Families 

Genera 

in Africa 

Endemic 

Genera 

1. Maizaniidae 3 3 

2. Cyclophoridae 4 3 

3. Pomatiasidae 2 2 

4. Hydrocenidae 1 - 

5. Veronicellidae 3 2 

6. Orculidae 2 2 

7. Chondrinidae 1 - 

8. Pupillidae 4 - 

9. Valloniidae 2 - 

63

10. Enidae 11 4 

11. Succineidae 3 - 

12. Puncidae 2 - 

13. Charopidae 25 25 

14. Arionidae 3 3 

15. Thyrophorellidae 1 1 

16. Vitrinidae 1 1 

17. Euconulidae 1 1 

18. Helicarionidae 1 - 

19. Ariophantidae 1 - 

20. Gymnarionidae 2 2 

21. Urocyclidae 50 50 

22. Aiilyidae 1 1 

23. Prestonellidae 1 1 

24. Ferussaciidae 2 1 

25. Subulinidae 21 14 

26. Achatinidae 13 13 

27. Ampuulariidae 10 8 

(Afer Zilch, 1959-60) 

Table 4: List of Fresh Water Snail Families 

from Africa 

S/N Families 

Subclass: Prosobranchia: Contains about 

30,000 species. They are mostly 

marine and possess gills. 

1. Neritinidae 

2. Patellidae 

3. Trochidae 

64

4. Helicinidae 

5. Fissurellidae 

6. Littorinidae 

7. Viviparidae 

8. Tympanotonidae 

9. Crepidulidae, etc. 

Subclass: Pulmonata: 

1. Lymnaeidae 

2. Planorbidae 

3. Ancylidae 

4. Physidae 

5. Orthalicidae 

6. Bulimulidae 

7. Dryomaelidae, etc 

Subclass: Opisthobranchia: Contains about 

1,100 species and all are exclusively 

marine. 

1. Hydatina 

2. Philene 

3. Runcina 

4. Aplysia 

5. Doris and 

6. Eolis. 

African fresh water systems have rich and abundant 

malacofauna. Most prosobranchs are edible and in addition 

to the terrestrial pulmonates, freshwater pilids, ampullarids 

and neritids are avidly eaten. In addition, the common 

edible snail species include: 

Helix aspera 

65

Helix lucorum 

Helix pomatia 

Burtoa nilotica 

Caracolus marginella 

Cepaea horteusis 

Cepaea nemoralis 

Cernuella virgata 

Euglandina rosea 

Ligus intertinctus 

Megalobulimus oblongus 

Metachatina kraussi 

Oxychilus cellarius 

Theba pisana 

Veronicella sloanei 

Zachysia provisoria 

Limicolaria flammea 

Limicolria chlemys 

Limicolaria martenois 

Otala vermiculata 

Otala lacteal 

Cornus aspersa 

Limicolariopsis 

Perideriopsis 

Pseudoachatina 

Columna columna 

Columna leai 

Helix adanensis 

Helix anotostoma 

Helix melanonixia 

Helix thiessiana 

66

Helix nucuea 

Helix aperta 

Arianta arbustorium 

Perforatella incarnate 

Achatina achatina 

Achatina achatina albopicta 

Achatina achatina albopicta 

Achatina achatina allisa 

Achatina achatina balteata 

Achatina achatina craveni 

Achatina achatina dammarensis 

Achatina achatina fulgurate 

Achatina achatina monochromatica 

Achatina achatina togoensis 

Achatina achatina bayoli 

Achatina fulica 

Achatina glutinosa 

Achatina immaculate 

Achatina iostoma 

Achatina iredaleri 

Achatina mulanjensis 

Achatina murrea 

Achatina nyikaensis 

Achatina panthera 

Achatina passagei 

Achatina reticulate 

Achatina schinziana 

Achatina schweinfurthi 

Achatina semisculpta 

Achatinaslyvatica 

67

Achatina smithii 

Achatina stuhlmanni 

Achatina tincta 

Achatina tracheia 

Achatina varicose 

Achatina variegate 

Achatina vignoniana 

Achatina weynesi 

Achatina zebra 

Achatina bequaerti 

Achatina tavarensiana 

Achatina elegans 

Achatina depravata 

Achatina roseolabiata 

Achatina bicarinata 

Achatina buylaerti 

Achatina camerunensis 

Achatina churchilliana 

Achatina cinamomae 

Achatina crawfordi 

Achatina degneri 

Achatina dimidiate 

Achatina drakensbergensis 

Achatina gabonensis 

Achatina granulate 

Achatina knorri 

Achatina limitanea 

Achatina machachensis 

Archachatina calachatina marginata 

Archachatina calachatina marginata ovum 

68

Archachatina calachatina marinae 

Archachatina calachatina montistempli 

Archachatina calachatina omissa 

Archachatina calachatina papyracea 

Archachatina calachatina parthenia 

Archachatina calachatina purpurea 

Archachatina puylaepti 

Archachatina semidecussata 

Archachatina semigranosa 

Archachatina simplex 

Archachatina ustulata 

Archachatina ventricosa 

Archachatina vestita 

Archachatina marginata suturalis 

All these snails can be eaten and are actually consumed in 

many parts of the world. For example, in West Africa 

(Ghana and Nigeria) snails are served as a delicacy in 

taverns, hotels and restaurants and are also eaten 

domestically in individual homes. Some of the West 

African species are the largest snails in the world. The 

freshwater prosobranchs are also widely eaten. 

Generally snails are delicacies in French cuisine, where the 

name escargot evokes culinary delight. In the English 

language menu, escargot is generally reserved for snails 

prepared with traditional French recipes (served in the shell 

with a garlic and parsley butter). Snails are also popular in 

Portuguese cuisine where they are called in Portuguese 

“cavacois” and serve in stewed (with different mixtures of 

white wine, garlic, piri piri, oregano, coriander or parsley, 

69

and sometimes chourico). Bigger varieties called 

“caracoletas”, are generally grilled and served with a butter 

sauce, but other dishes also exist such as “feijoada de 

caracois”. Overall Portugal consumes about 4000 tonnes of 

snails each year. 

Traditional Spanish cuisine also uses snails (“caracoles”), 

consuming several species such as Helix aspersa, Helix 

punctata, Helix pisana or Helix alonensis among other 

small to medium sized varieties are usually cooked in 

several spicy sauces or even in soups, while the bigger ones 

may be reserved for other dishes such as the (a paella-style 

rice with snails and rabbit meat dish) “arroz con cotio & 

caracoles” or “carecols”. In fact the Catalonians have a 

snail celebration they call “Aolec del cargol”. Here snails 

are called cargols or caragols. The gill the snails inside 

their shells and eat it after dipping in garlic mayonnaise or 

a la gormanda, boiled in tomato and onion. 

In Greece snails are popular in the Island of Crete but are 

also eaten in other parts of the country and can even be 

found in supermarkets, some times pleaced alive near 

partly refrigerated vegetables. In this case, snails are one of 

the few live organisms sold at super markets as food. They 

are eaten either boiled with vinegar added or sometimes 

cooked in a casserole with tomatoes and squashes. Another 

cooking method is the “Koali Bourbouristi” traditional 

Cretan dish, which consists of fried snails in olive oil with 

lemon. In sicily snails are known as babbaluciiad and 

widely eaten. 

In a nutshell, snails are eaten in several countries in the 

world even as far back as thousands of years beginning in 

the Pleistocene. They are especially abundant in Caspian 

70

sites in North Africa but are also eaten throughout the 

Mediterranean region, where their fossil remains are found 

in archaeological site dating between 12,000 and 6,000 

years ago. However it should be noted that wild caught 

land snails that are undercooked can harbour a parasite that 

may cause a rare kind of meningitis but this does not stop 

specialized snail caviar growing in popularity in cuisines 

around the world. 

(d) SNAILS AND HUMAN HEALTH 

Due to its slowness, snails have traditionally been seen as a 

symbol of laziness. In Judeo – Christian culture, they have 

often been viewed as manifestations of the deadly sin of 

sloth. Psalm 58 vs 8 implies that slimy track of a snail is a 

sign that is will eventually wear itself away. Snails were 

also widely noted and used in divination. The Greek Poet 

Hesiod was noted to have said that snails signified the time 

to harvest by climbing the stalks, while the Aztec moon 

god “Teccizteatl” bore shell on his back. This symbolized 

rebirth. The snail’s penchant for appearing and 

disappearing was analogized with the moon. Despite all 

these folk tales, snails actually constitute a serious health 

problem for man. For example, the giant African snails are 

carriers of the rat parasite, Angiostrongylus cantonensis. 

This parasite can be contracted by man (zoonosis) by 

ingesting improperly cooked snail meat or by handling live 

snails and transferring some of the mucus (slime) to the 

human mucus membranes such as those in the eyes, nose 

and mouth. They develop in man to cause a form of 

meningitis. 

71

Perhaps the greatest disease problems of man traceable to 

snails have been linked to trematode parasites using the 

snails as intermediate hosts for their larval stages. Snail 

borne diseases have been counted as one of the most 

important public Health problems second only to mosquitoborne 

diseases. In the past there was a stable ecological 

relationship between man, snail and parasites. The human 

population was low, thus with a low level of diseases. 

Currently the explosive growth in human population with 

its attendant poor sanitary conditions and increased 

mobility of infected people, more and more people get in 

contact with infective stages of the parasites in the snails. 

Thus an excellent condition is presented for parasite 

transmission making snail borne diseases serious public 

health problems today. 

Some of these snail borne diseases include: 

(a) Schistosomiasis: 

Schistosomiasis or bilharsiasis is the commonest 

parasitic zoonoses first recorded in Egypt about 

4000 years ago. The parasite was isolated in 

1851 by a doctor known as Theodore Bilharz in 

the mesenteric veins of an Egyptian. It was 

named Bilharzia and later changed to 

Schistosomiasis of the unique appearance of the 

body of the male parasite which looks as if it is 

split longitudinally to produce a canal in which 

the female positions herself. 

This parasite is a trematode that belongs to the 

subclass Digenea; the order prosostomata and the 

suborder strigiata. Their super family is 

schistosomatiodea. Sixteen species are known to 

72

infect man or animals. The five principal species 

that infect man fall into one of the three groups 

that are characterized by the type of egg 

produced as follows: 

(a) Eggs with lateral spine (S. mansoni) 

(b) Eggs with terminal spine (S. haematobium) (S. 

intercalatum) 

(c) Eggs that are round and minutely spined 

(tubercle) (S. japonicum; S. mekongi) 

The disease is endemic in 74 countries of the world. It is 

estimated that around 200 million people are infected and 

that between 500 and 600 million persons are at risk. 

Infections persist because of ignorance, poverty, poor 

housing, substandard hygiene practices and the availability 

of few if any, sanitary facilities. 

All schistomas species share the same basic life cycle. The 

eggs are passed in either urine (S. haematobium) or faeces 

(S. japonicum, S. mansoni, S. bovis, S. rodhaini, S. bovis, S. 

curassoni and S. intercalatum). Each egg contains a fully 

formed miracidium. On immersion in fresh water, 

particularly under condition of warmth and light they hatch 

almost immediately. The miracidium larvae which emerge 

swim actively by means of cilia with which they are 

covered and penetrate into the freshwater snail that is 

compatible to its species. The miracidia die in 16 – 32 hrs if 

they do not succeed in reaching a suitable snail 

intermediate host. The schistosoma is extremely host 

specific with regards to the snails in which they develop. 

73

The species of snails used depends on the geographical 

region but generally S. haematobium and S. intercalatum 

develop in snails of the genus Bulinus (Planorbidae). S. 

mansoni develop in Biomphalaria where as develop in 

Oucomelania. 

Through a series of asexual multiplicative division in the 

snail, a single miracidium will give rise to thousands of 

cercariae all of the same sex. 

When man enters the water the cercariae penetrate the skin, 

often between the hair follicles and after between 4 – 12 

weeks depending on the species, eggs start appearing in 

either urine or faeces. 

Persons with Schistosomiasis may be asymptomatic or may 

manifest a spectrum of disease conditions. Acute 

schistosomiasis or Katayama fever occurs after the initial 

exposure and infection in S. mansoni or S. japonicum. This 

febrile condition results as a result of hypersensitivity 

reaction to schistosomal antigens. The patients complain of 

flu like illness with fatigue, headache and might sweat 

without the snail intermediate host the infection of man or 

animals is impossible. 

Schistosomiasis is endemic in Nigeria and studies show 

that infection is focal and aggravated by developmental and 

agricultural projects. Several studies in Nigeria show that 

children within the age group 10 – 14 bear the most burden 

of the disease which depends on the human water contact 

patterns due to domestic, recreational and agricultural 

imperatives, and also follows the socio economic status of 

people in the endemic areas. Studies such as those of 

Cowper (1973), Iheagwam and Okafor (1984), Adekolu- 

John and Abolarin (1986), Anya and Okafor (1986), 

74

Okafor (1989, 1990, and 1992), Ozumba et al., (1989), 

Betterton and Fryer (1982), Fryer (1986), Emejulu et al; 

(1994), Anosike et al; (1992), Adewunmi et al.,(1990), to 

mention important few, are good for further reading to 

understand the epidemiology of the disease and the role of 

different snail species in its transmission. 

The studies further present check lists of freshwater snails 

in the various ecoological zones of Nigeria. Roles of the 

snails in the aquatic food chains and the prominent roles 

they play as intermediate hosts of trematode parasites of 

wild animals are pointed out. 

Table 5: Principal Freshwater Intermediate 

Host Snails 

Snail genera Snail Species Diseases 

Transmitted 

Lymnaea L. truncatula Fasciola hepatica 

L. pellagra 

L. natalensis 

Fasciola gigantica 

Neritina N. glabarata Fish and 

N. adamsoniana 

N. afra 

N. oweniana 

N. rubricate 

N. cristata 

N. nasalensis 

Bird flukes 

Bulinus B.Bulimus Clonorchis sp 

Bellamya fachsianus 

B. unicolor 

Lanistes L. Ovum 

75

L. libycus 

L. varicus 

Pila P. luzonica 

P. ovata 

P. atricana 

P. wernei 

Alocinma Alocinma 

longicornis 

Gabiella G. humerosa 

G. purvipila 

G. verdicourti 

Semisulcospira S. libertine 

S. amaurensis 

Potadoma P. buttikoteri 

P. bicarinata 

P. liberensis 

P. freethi dykei 

P. moerchii 

Melanoides M. tuberculata 

M.. Manguensis 

M. voltae 

Cleopatra C. bulimoides 

Pachymelania P. fusca 

P. aurita 

P. byronensis 

P. freethi dykei 

P. moerchii 

Melanoides M. tuberculata 

M. manguensis 

M. voltae 

Cleopatra C. bulimoides 

Pachymelania P. fusca 

Bird flukes 

Clonorchis sp 

Lung flukes 

Paragonimus 

(Lung flukes) 

76

P. aurita 

P. byronensis 

Gyraulus G. costulatus 

Indoplanorbis I. exutus S. indicum 

S. spindale 

Biomphalaria B. pfeifferi 

B. rhodesiensis 

B. salinarum 

B. choanomphala 

B. smithi 

B. stanleyi 

B. Alexandrian 

B. angulosa 

B. sudanica 

B. camereunensis 

B. glabrata 

S. lhistosoma 

S. rodhaini 

S. mansoni 

Robertisiella R. obertsiella Malaysiam 

Schistosoma 

Thiara T. granifera Paragonimus 

Bulinus B. africanus 

B. abyssinicus 

B. globosus 

B. jouseaumei 

B. nasutus 

B. productus 

B. umblicatus 

B. ugandae 

B. forskalii 

B. scalaris 

B. camerunensis 

B. senegalensis 

B. truncatus 

Schistosoma 

heamatobium 

Avian Schistosoma 

S. boris 

S. curassoni 

S. maygrebowiei 

S. mattheei 

S. intercalatum 

77

B. tropicus 

B. reticulatus 

Oxyloma O. elegans 

Bithynia B. tentaculata 

Para P. manchouricus 

fossarulus 

Ferrisia F. ebunensis 

Succinea S. putris 

Cerithidea Cerithidea sp 

Segmentina S. angustus 

Physa P. waterloti 

Pironella Pironella sp 

Oncomelania O. anadrasi 

O. hupensis 

O. nosophora 

o. lindoensis 

O. formosana 

O. chiui 

Tricula T. aperta S. mekongi 

The intra-molluscan schistosome larvae are of no direct 

clinical importance, certain features are of interest. As the 

miracidium penetrates the snail, the tegumental plates, and 

cilia are shed and the rest of the body reorganizes into a sac 

of reproductive cells which absorbs nutrients from the snail 

tissues known as the mother sporocyst. The daughter 

sporocysts have even greater nutritional requirements 

which are best met in the digestive glands and gonads of 

the snail to which they migrate before beginning full 

development. The most important aspect of infection in the 

snail is the massive asexual multiplication which allows 

78

one miracidium the potential of producing many thousand 

cercariae which, when released from the secondary 

sporocysts, migrate through the tissues into the blood 

sinuses and escape from the snail through the walls of the 

superficial blood vessels of the mantle, gill or pseudobrach. 

The net result of prolonged production of cercariae 

increases the chance that one cercaria will eventually infect 

man or other suitable hosts. 

It is important to note that the snails do not accept infection 

entirely passively (Loker et al., 1984). Amoebocytic cells 

originating from the heart epithelium attack invading 

foreign bodies, possibly in conjunction with soluble factors 

which themselves are derived from the amoebocytes. This 

reaction helps to destroy many primary sporocysts within a 

few days of penetration. In many snail species, the young 

snails are susceptible, but progressive changes in the 

composition of the haemolymph result in increasing 

resistance with age (Michelson, 1986). It is further 

important to note that some cercariae migrating through the 

snail tissues are trapped and destroyed in granulomatous 

reactions. 

These infection processes of the snail borne trematodes can 

be broadly divided into oral and(or) transdermal routes of 

the worms’ larval stages which have been previously 

released from the infected snails. During development 

within the human body clinical cymptoms appear. 

These symptoms include uticaria, fever, ascites, 

haematemesis, carcinoma and hepatosplenomegaly. After 

maturation and depending upon the species of infection, the 

resultant adult worms reside within the blood vasculature 

system or internal body cavities of the human hosts. Unlike 

79

other parasitic infections the snail borne worms do not 

directly replicate inside the body but rather produce 

copious amounts of eggs. It is these eggs, which depending 

on the species of worms that are voided into the 

environment through sputum, urine or faeces, facilitating 

the life cycles of the parasites. 

The eggs that fail to exit the body often become trapped in 

host tissues and organs and ultimately trigger the 

immunopathology associated with the disease. 

(b) Fascioliasis 

Another name for this disease is liver fluke 

disease. This disease is caused by the infection 

with the trematode Fasciola (F. hepatica and F. 

gigantica). The source of infection is ingestion of 

raw aquatic vegetation contaminated with 

encysted metacercariae such as lettuce and green 

salad, grasses and water crests. 

Fasciola passes its life cycle in two different 

hosts: sheap, goat and cattle are the definitive 

hosts which snails of the genus Lymnaea are the 

intermediate hosts. The undifferentiated ovum 

develops into a miracidium under moist 

conditions in 9 – 15 days at 22 – 25 o C. The 

miracidiae which hatch out of the eggs lives for 

only eight hours and can move in a film of 

moisture on damp pastures. Further development 

takes place after free living miracidium 

penetrates an amphibious snail. More than 20 

species of Lymnaea have been incriminated as 

capable of acting as intermediate host for 

Fasciola. 

80

In the snail the miracidium metamorphoses into a 

sporocyst, rediae, daughter rediae and cercariae. 

The cercariae emerge from the snail and eneyst 

on water cress, grass, barks or soil. When 

ingested by a definitive host the metacercariae 

exyst in the duodenum. The disease runs an acute 

and chronic phases. The chronic phase occurs 

when the mature fluke enters the bile duct and 

symptoms pertaining to obstruction of the bile 

duct or inflammation of the duct occurs. 

(c) Fasciolopsiasis (Ginger worms) 

This disease is caused by the parasite 

Fasciolopsis buski which was earlier called 

Distoma buski. The parasite is also known as the 

Giant intestinal fluke of man. Its definitive hosts 

are man, pig or dog. 

The molluscan hosts are of the genus 

Segmentina. The eggs are passed in the faeces of 

the definitive hosts. These eggs hatch in 3 to 7 

weeks in water having a temperature of between 

80 and 90 o F to give rise to the ciliated miracidia. 

These penetrate the suitable snail hosts and 

develp into sporocysts, then into rediae, daughter 

rediae (or rediae II) and cercariae. The cercariae 

emerge from the snails and get converted into 

metacercariae on the outer covering of water 

chestnuts. 

Human beings get infected by eating 

contaminated raw water plants especially when 

peeling off the outer layers with their teeth. 

81

The disease is confined to Southeast Asia. 

Countries affected include: China, Taiwan, 

Thailand, Vietnam, Bangladesh, and India 

(Assam and Bengal). About 10 million people 

were estimated to be infected worldwide by 1947 

and must have surpassed 15 million giving the 

fact that its incidence varies between 5 – 50% in 

endemic areas. 

(d) Paragonimiasis (Lung fluke disease) 

This is a chronic infection of the lungs caused by 

the trematodes of the genus Paragonimus. 

Paragonimus westermani: is the commonest 

species but in Southeastern Nigeria the common 

species is Paragonimus uterobilateralis found 

Prof. Nwokolo and his colleagues around 

Okigwe, Ezinachi and Umuguma. It is a common 

human parasite in the Far East (Japan, Korea, 

Manchuria, China, Southeast Asia and Papua 

New Guinea). In the Indian sub continent it 

occurs in Bengal, Tamilnadu and Mumbai. 

Man gets infected by eating raw or poorly 

cooked crab or crayfish which has been 

contaminated with metacercariae of the parasite. 

The parasite passes its life cycle in 3 hosts: one 

definitive and two intermediate hosts. 

The definitive hosts are mammals, domestic 

animals, tigers and leopards. The intermediate 

hosts include a first host which is a freshwater 

snail of the genus Melania in Southeast Asia. 

82

While Potadoma and Semisulcospira serve as 

hosts in West Africa. The second host is either a 

freshwater crayfish or crabs (Potamon or 

Sudanonautes). 

The golden brown operculate eggs reach the 

bronchioles from where they are coughed up and 

excreted in sputum or swallowed and passed out 

in faeces. On reaching water the miracidia hatch 

out and penetrate into fresh water snails (e.g. 

Semisulcospira libertina, S. amaurensis, Thiara, 

Potadoma, Melania). 

Table 6: Classification of Trematodes 

Infecting Man 

S/N Group Location & Examples 

A. Dioecious 

blood flukes 

. Hermaphroditic 

flukes 

They live inside veins in various 

locations. E.g.: 

(i) In the vesical and pelvic 

venousplexuses - Schistosoma 

haematobium 

(ii) In the inferior mesenteric vein 

– S. mansoni 

(iii) In the superior mesenteric vein 

– S. japonicum 

They live in the lumen of various 

tracts: 

(i) Biliary tract – Clonorchis 

sinensis 

– Fasciola spp 

– Opisthorchis 

spp 

(ii) Gastrointestinal tract 

83

(a) Small intestine 

– Fasciopsis buski 

– Heterophyes heterophyes 

– Metagonimus yokogawai 

– Watsonius watsoni 

(b) Large intestine 

– Gastrodiscoides hominis 

(iii) Respiratory tract 

– Paragonimus spp. 

In the snails the miracidia develop into sporocysts followed 

by two generations of rediae and later (3 months after) give 

rise to very short tailed cecariae (micro- cercous Xiphidio- 

cercariae). These emerge from the snail and swim in water 

and can survive for 24-48 hours. If they find freshwater 

crabs they enter. 

The crab species include Potamon, Sesarma, Eiocheir and 

Sudanonautes or freshwater crayfish – Astacus. They 

penetrate and encyst in the gills or muscles as 

metacercariae. The Freshwater crustaceans can probably 

become infected by ingesting unencysted cercariae in the 

water or even inside infested snail. 

The disease is insidious beginning with a non-specific 

cough that becomes chronic and is productive of blood 

tinged sputum known as endemic haemoptysis. Patients 

also experience pleural pain and dyspnoea. Depending 

upon secondary bacterial infection there may be 

pneumothorax and pleural adhesion. Lesions in the brain 

can lead to seizures. 

(e) Clonorchiasis 

84

Clonorchiasis is caused by Clonorchis sinesis. 

The species was earlier known as Opisthorchis 

sinensis. Infection due to this parasite is largely 

confined to Vietnam to Japan (Including Korea, 

Taiwan, China). It affects about 10 million 

persons. 

Humans are the principal definitive hosts, but 

dogs and other fish eating canines act as 

reservoir hosts. Two intermediate hosts are 

required to complete its life cycle, the first being 

snails and the second is fish. 

The eggs passed in faeces contain the ciliated 

miracidia. They do not hatch in water, but only 

when ingested by suitable species of operculate 

snails such as Parafoassarulu, Bulimus, 

Alocinma. The cercariae escape from these snails 

and swim about in water, waiting to get attached 

to the second intermediate host, suitable 

freshwater fish of the carp family. They then 

shed their tails and encyst under the scales or in 

the flesh of the fish to become in about 3 weeks 

the meta cercariae which are the infective stage. 

Human infection occurs when such a fish is 

eaten raw or improperly processed. Frozen, dried 

or pickled fish may act as source of infection. 

Infection may also occur through fingers or 

cooking utensils contaminated with the meta 

cercariae during preparation of fish for cooking 

(f) Other Trematodes of Medical Importance 

(i) Dicrocoeliasis: Disease caused by the 

trematode parasite Dicrocoelium dendriticum 

85

(known as the lancet fluke). This fluke is a 

very common biliary parasite of sheep and 

other herbivores and accidentally infects Man 

in Japan and China, Europe, N. Africa far 

East and Northern Asia. 

Eggs passed in faeces are ingested by land 

snails Limicolaria Cercariae appear in slime 

balls secreted by the snails and are eaten by 

ants of the genus Formica in which the 

metacercariae develop. 

Infection occurs when the hosts accidentally 

eat the ants while feeding. Spurious 

infections have occurred in persons who ate 

infected sheep liver and can pass eggs in 

faeces for about a week or several days. 

(ii) Eurytrema pancreaticum, is a related fluke 

and is commonly present in the pancreas, is a 

related fluke and is commonly present in the 

pancreatic duct of cattle, sheep and monkeys. 

Occasional human infection has been noticed 

in China and Japan. 

(iii) Intestinal Flukes: 

A number of fluke parasites parasitize the 

human intestine. These include Heterophyes, 

Metagonimus, Wastonium and Echinostoma. 

Only one fluke Gastrodiscoides hominis 

parasitizes the human large intestine. 

The snail intermediate hosts for these are 

presented in table 7. 

86

Table 7: Showing a list of trematode parasites, their 

intermediate hosts and reservoir hosts. 

S/N Trematode 

Parasite 

Snail 

Intermediate 

Hosts 

1. Heterophyes Pironella 

Cerithidea 

Other Hosts 

Cats, dogs 

foxes and 

otherfish eating 

mammala 

2. Metagonimus Pironella 2 nd host Trout, 

Reservior dogs, 

cats, pigs, 

pelican and 

other fish 

3. Metorchis Freshwater 

snails 

eating birds. 

Sled dogs and 

freshwater fish 

(white sucker) 

4. Watsonium not known Primates 

Africa Asia. 

in 

5. Gastrodiscoides Freshwater Pigs, monkeys, 

snails mouse 

deers. 

and 

6. Echino stoma Snails and Man 

Fresh 

snails 

water 

7. Alaria Achatina Man, foxes and 

87

8. Gymnophalloides Marine 

oysters 

freshwater 

snails 

9. Nanophyetus Freshwater 

snails 

10. Mesocoelium Achatina 

Archaehatina 

other canids. 

Shore birds and 

man 

Dogs, foxes, 

and wolves. 

Sailmonial fish, 

fish eating 

birds, man and 

other animals. 

Beyond these trematode infections that must undergo 

multiplicative development in snails, there is other roles 

snail play in human health. The land Helix or snail has been 

used in medicine since antiquity and are used to prepare 

many formulations. Scientific knowledge recorded that 

Hippocrates proposed the use of snail mucus against 

protoceler and that snails increased the speed of delivery. It 

was also noted that in folk medicines, snails are used to 

prepare the “sovereign remedy to treat pain, abscesses and 

other wounds. Snails had been part of the various 

preparations recommended in the past for external uses and 

internally for symptoms associated with tuberculosis and 

nephritis. The 19 th century saw a renewed interest in the 

pharmaceutical and medical use of snails. This interest in 

snail did not start now, for example, an entire paragraph 

was to snails indicating that usage of snails had begun by 

1945. The America FDA showed a substance ziconotide 

(SN xii), a synthetic peptide coming from snails venom in 

1999. Pre clinical and clinical studies of this new drug are 

88

promising and show reduction of pain intensity by 53% 

even in patients insensitive to morphine. 

Snails from Africa are the best but they must be prepared in 

an uneven numbers. Anaemia patients feel much better if 

they drink snails. Eating snails was prescribed for cases 

like vertigo, fainting fits, and fits of madness. The snails 

should be crushed in wine. It was recommended at the time 

that snails could be used against hydrops foetalis. Snails 

have also been recommended against anthrax, and can cure 

hernias. Other ancient uses of snails are as astringents, first 

and second degrees, acute and chronic chest ailments, 

intestinal irritations, chapping, and efflorescence of sores. 

Transparent yellow oil extracted from Helix pomatia can 

cure marasmus. Snails have also been used with success 

against inflammations especially against cough and cold, 

bronchitis, catarrhs, asthma, haemoptysis, tonsillitis, 

pharyngitis, hoarseness, sore throat, influenza, croup, 

nervous cough of children, lung diseases, such as 

pneumonia, and stomach or intestinal cramps, gastritis, 

gastero-enteralgia, headaches coming from disorders of the 

stomach, cough that follows or comes with inflammatory 

skin disorders, measles, scarlet fever, small pox, erysipelas, 

etc. singers find them to be very active aids against several 

alterations of the voice. 

Formulations made from Helix pomatia are now confirmed 

to cure whooping cough and chronic bronchitis. The fluids 

from snails are touted to have autiseptic, fluidizing 

properties. As much as 30 enzymes have been isolated 

from the digestive nucus, pancreostomach, the muscle and 

lymph fluid. Mucolytic and bacteriolytic properties of 

89

snails are noted as well as the antispasmodic activities, 

musculotropic effects and sedative properties. 

In 1999 Pons and associates demonstrated that the bronchorelaxant 

effect of helicide was due to release of E2 

prostaglandins and that this was inhibited by pre-treatment 

with indomethacine. Scientists have also isolated a lectin 

called Helix pomatia agglutinin used as a prognostic 

indicator for some carriers such as those of the breast, 

storage and fixation of histological preparation of these 

tissues. This latter activity is attributed to the actions 

against an HPA associated glycoproteins that are linked to 

metastasis of cancer. 

Investigators have also shown that in populations eating 

snails, that the life expectancy was high (about 7 countries 

studied), there was less number of deaths due to cardio 

vascular events than non snail eating populations. This was 

suggested to arise from the rich fatty acid content of their 

diet and the natural herbs that they eat. Snail meat is said to 

be rich in a-linolenic acid that has been reported to have a 

protective effect against cardiovascular disease. 

In 2000 a substance called Conotoxin (TVIIA) was 

extracted from Conus tulipa a fish eating sea snail by 

Scientists in University of Utah, USA and another peptide 

called Contryphan-Vn was also extracted from the venom 

of sea snails. Recently it has been found that snails are 

helping scientists at the University of Sussex to explore 

ways of treating memory loss in humans by Drug 

manufacturers looking for ways to create a “Viagra” for the 

brain (that could alleviate memory loss). It is well known 

that one of the distressing symptoms of Alzheimer’s 

disease is memory loss. It is also known that people with 

90

memory loss have a devastating consequence of long term 

impaired memory and it occurs in millions of people. Using 

materials from snails, scientists are putting together 

information that will help in understanding and ultimately 

preventing and treating memory disorders. They are 

looking for brain molecules that are crucial for the building 

up and maintenance of long term memory and learning. 

People are now attempting to enhance, by chemical 

activation or inhibit those functions in the common pond 

snails. 

Snails are ideal for this kind of study because humans and 

pond snails actually share some important characteristics 

unchanged by evolutions. These include the basic 

molecular mechanisms that control long term memory and 

learning. These processes involve the activation or 

suppression of a protein CREB which is a key to the 

formation of long term memory and are found in species 

ranging from molluscs, flies, rats to man. These responses 

can be tested by classical Pavlovian experiments that bring 

about a conditioned response. It has been reported that a 

snail exposed to the smell of pear drops and other foods 

will respond weeks later to the smell of pear drops by 

rhythmically moving its mouth parts in anticipation of 

food, even when none is provided. This shows that the snail 

now has a memory associating the smell of pear drops with 

the arrival of food – a learned and remembered response. 

This “flash bulb” response as it is called, created by just 

one response to a stimulus is complemented by another test 

where the snail is exposed to a tickling stimulus before 

food is introduced. It takes very long for the snail to 

associate this tickling with the arrival of food. Snail have 

large neurones which are easily identified, manipulated and 

91

observed under a microscope thus making them a vital tool 

to be explored in studies on learning and memory 

processes. 

To the Japanese the giant African snails are presumed to 

have great medicinal properties. The possible curative 

power of snails in getting rid of tuberculosis was 

canvassed. It is also believed that slugs put in coconut milk 

cures asthma. A curative substance that is extracted from 

the snail known as “Ishinoto negligin” now known to be 

orthocalcium phosphate is believed to be the medicinal 

substance. This chemical is claimed to cure some kidney 

diseases, anaemia, diabetes, uticaria, circulatory disorders 

etc, to improve constipation, hemorrhoids and to prevent 

influenza. It is claimed to improve virility and vitality; to 

perpetuate beauty and clear the skin. In the past, those who 

sing always are advised to eat snails. 

In a keynote address by Tazwa in 1934 he said “buying 

meat and fish for your table is unnecessary when you eat 

snails, and there will be no sickly person in the house, 

doctors and kept away and it brings smiles to the home”. In 

addition he urged the cultivation of Achatines and he made 

numerous recommendations for increasing production and 

simplifying the task for raising the snails. A species known 

as “Shirafuji” in Japan was being promoted in the early 

thirties as a new industry with high profit making 

potentials. 

In the United States, it has been shown that some edible 

snails also play an important role in American folk 

medicine. In addition to the nutritional value of snail meat. 

Baratou (1988) in California showed that the glandular 

substances from edible snails cause agglutination of some 

92

acteria. This bacteriostatic activity is of value against a 

variety of ailments, including whooping cough. 

In Ghana the bluish liquid obtained from the shell of the 

tiger snail when the meat has been removed is believed to 

be good for infants’ development. The high iron and 

vitamin contents are considered important in the treatment 

of anaemia. At the imperial courts of Rome it was reported 

that snail meat has aphrodisiac property and was often 

saved to visiting dignitaries in late evenings. 

(d) SNAILS AND AGRICULTURE 

In aquaculture (controlled raising of animals in water) the 

primary goal is to produce more foods. This type of 

agriculture, improves the quality of the organisms and their 

productivity. The main animals used in aquaculture are 

fish, crustaceans and molluscs. Among the molluscs the 

viable forms are mussels, oysters, clams and prosobranchs 

(e.g. Pilidae, Ampullaridae and Neritidae). 

Available data suggest that over 12 million tonnes of meat 

are derived from aquaculture every year and 17.0% of these 

are molluscs. The rest comprise of sea weeds, algae, 

crustacean and fish. The most likely species of snails that 

will benefit from increased deployment in aquaculture are 

Pila wernei (Philippi), Lanistes varicus, Ampullarium sp, 

Lanistes ovum, Pila ovata and other groups are locally 

classified in Igbo land as ”akpakolo”. These are all 

freshwater Prosobranchs. About 34 developing countries 

and all developed economies have the potentials and infact, 

have started deploying aquaculture for increased animal 

and aquatic plants production. The need for finding 

employment of the teeming populations of youths world 

93

wide has served to renew interests in practices like oyster 

cultures, mussel farms and aquatic snail farms , shrimp and 

crayfish farms. Ways will be found for reducing the 

impacts of increasing costs of feeds, shortage of fertilizers 

that are required for improved aquaculture production as 

well as combating aquatic pollution due to uncontrolled 

application of pesticides, and herbicides. 

A number of technological advances have occurred in 

aquaculture since it was developed about 4000 years ago 

mainly in South east Asia and China. A good example of 

such advances is the catfish farming in USA, prawn and 

shrimp farming in Canada and elsewhere in the world. 

These modern technologies can be adapted for snails to 

keep up with the requirements of rapid expansion of 

productions. 

In regions where intense crop farming is extensive lime is 

always in serious demand. In such places it is common for 

the local farmers to use Achatina or other snails’ shells 

which they reduce in “Lime Kilns” as a by product in the 

preparation of snail meals. The shell of Melania and 

Corbiculaare are being used in this manner in Malaysia . 

In areas where the soil is excessively acidic, as is the case 

in humus soils of forests, the alkalizing effect of adding 

crushed shells would be desirable as far as most crops are 

concerned. But on the other hand, in coralline soils which 

are already excessively basic and should not have more 

calcareous materials added to them. This suggests that if 

snail shells are ever used in formulating fertilizers, two 

different kinds should be made available: 

(a) one with shell fragments and 

(b) one without shell fragments. 

94

The thin, quickly leached soils of tropical areas need 

enriching of some sort if they must be used for much more 

than two or three years. Besides the shells, the meat of the 

snails can be used as fertilizers. Primitive peoples in Asia 

were known to use disintegrating animal flesh to replenish 

the soil as plant growth promoting constituents in depleted 

soils. These use snails by putting them in metal oil drums 

and allowing them to stand in the hot sun until the snails 

died. They were allowed to reach a high degree of 

putrefaction. These rotting, maggot infested snails were 

then scooped out of the shells. Then the putrid slimy, 

odoriferous mess was then added as a fertilizer in farms. It 

had been found that crops that benefited from snail 

fertilizers had generally better quality. The use of this 

process introduced two disadvantages: 

1. The inadequately covered oil drums permitted 

the escape of fly maggots as a threat to public 

health. However modern aquaculture practices 

suggest that these maggots could be harvested 

and used to feed fish in aquaculture pens thus 

reducing giving them positive value. 

2. Addition of this and the crushed shells to the soil 

moved the soil P H even more strongly in a basic 

direction. 

This latter disadvantage has been eliminated as it is now 

known that when only “liquid” fractions were used by 

drawing off and diluting with ten parts of water before 

being added to the soil (Peterson, 1957), it becomes 

enriched. 

95

Snail meat can also serve as salt water fish baits. In the 

U.S. the raw flesh of the Philippine pond snail Pila 

luzonica is used as a bait for line fishing. 

Snails can be used for poultry feed. Small living snails 

were experimentally given to chickens with no success. 

They would occasionally pick at them. But Van Weel 

(1948) found that chickens would not reject well crushed 

snails but that they would not take to them as avidly as 

ducks invariably do. Other studies insist that chicken ate 

snails raw, boiled or roasted, but seem to prefer them 

crushed and boiled. In the Dominican islands, the freshly 

killed endemic snails are pounded with corn meal before 

they are fed to the chicken. The general consensus is that 

chicken and ducks accept snails when crushed and boiled. 

Another method which showed increased acceptability is 

that a portion of the snail shells were ground up and 

combined with snail meal as an added source of calcium 

carbonate. In the proper proportion, it would obviate the 

necessity of using oyster shell or other sources of bone 

meal. 

Snails are also used in feeding livestock and they are 

incorporated in the daily rations of pigs. Experiments show 

that pigs eat snails live, boiled or chopped. The general 

agreement is to boil and de-shell the snails before feeding 

the pigs with them. 

Snail meals can be produced and used as fertilizers or as 

supplemental feeds. In both cases it would be desirable to 

dehydrate the snails and reduce them to a powder or meal. 

In this form, it could be stored and used when needed either 

as a fertilizer or as feed supplement. The value of snail 

meal is in the high percentages of phosphates and lysine. 

96

Snails are also pests of crops wherever they exist in the 

wild. Further information can be obtained in the publication 

slugs and snails in world agriculture edited by Henderson 

(1989). The snails ravage crops, vegetables and flower in 

gardens and farm lands especially during the rainy seasons. 

Its activities had to the restriction and quarantine of the 

snails especially the giant African land snails into many 

developed countries most especially in U.S. This has led to 

the US Department of Agriculture issuing warnings and 

placing embargo on importation of live snails. The snails 

are voracious plant feeders and can be very destructive to 

landscape and homes. They are known to eat at least 500 

different types of plants including pea nuts, beans, peas, 

cucumbers and melons. 

SNAIL FARMING 

Snail farming is the keeping of snails in a confined 

environment under human control and management. 

Attempts at snail domestication have been documented 

from Roman times (Elmslie,1982). In Africa, the feasibility 

of farming snails has been demonstrated by a number of 

researchers (eg.Ajayi,1971; Plummer,1975; Ajayi et 

al.,1978; Hodasi, 1979; Okafor, 2000). The types of snails 

slated for cultivation are Achatina, Archachatina, Helix, 

Limicolaria, etc. Snail farming: is an activity that involves 

production, management, harvest and sales of snails as well 

as a means of supplementing household income and protein 

supply. Snails are marketed fresh or smoke-dried, but their 

supply is seasonal. Three discernible attitudes are known 

concerning snail consumption i.e. in one group snails are 

avidly consumed in large numbers; in another group, 

97

consumption of snails is a taboo; while another group do 

not ordinarily consume snails ,they prefer other sources of 

protein but would take the snail in seasons 0f abundance 

when snails are cheap. 

The usefulness and importance of snail farming include: 

1. It is an alternative activity to bushmeat 

hunting and trading 

2. Provides a source of food/meat for protein 

supplementation 

3. It generates income 

4. It is a source of medicine (e.g. waist pain 

and anaemia) 

5. It provides employment 

6. It contributes to biodiversity conservation 

7. It does not use large expanse of land or 

agricultural inputs as other agricultural 

activities 

8. It makes use of organic materials. 

9. The activities are environmentally 

friendly. 

Many species of snails (helicidae and escargot) can be 

farmed. The following are the steps taken in farming snails: 

(a) Selection of a suitable site that is preferably flat 

surface. 

(b) Selection of initial stock of snails. 

(c) Construction of pens 

(d) Fencing of the site 

(e) Installation of equipment 

and 

98

(f) The management of the snail farm. 

HOUSING 

Snails can be housed in many types of containers, but all 

must be able to withstand the warm humid conditions that 

are necessary. The common ones include old tyres, old 

basins / clay water pots, wooden or bamboo boxes and dug 

holes. An aquarium tank or plastic pet cage would make a 

suitable home. One sized 40cm x 25cm would house an 

adult snail or several smaller specimens. An escape proof 

top is necessary and preferably one that allows for some 

ventilation. A glass or Perspex, slightly raised on plasticine 

will often suffice. A layer of soil should be provided for the 

snail to burrow into. A light misting is necessary, as high 

humidity may be an essential requirement. Snails should be 

able to approach water, usually provided in a water dish. 

This they may drink. The environment should also contain 

other surfaces over which the snails can move. They need 

softish irregular surfaces. Hollows of tyres can be used as 

convenient hides. A lump of chalk or limestone is an 

essential furnishing of the pens. Snails have a huge 

requirement for calcium to build up this mineral 

requirement. 

Large scale farming involves the use of large cages and 

fenced pens, Polyethylene tubes and wide expanse of lands. 

Most snail farms may require mild climate, with high 

humidity and a wide range of temperatures. 

99

METHODS 

There are several different methods used to farm snails. 

The factors that determine the choice of method are the 

scale of the enterprise, the stage of development of the 

snails and the habit of the snail. 

Intensive method: This is practiced by large scale 

commercial farmers requiring high capital. 

Semi Intensive method: In this method the cost outlay in 

low and is recommend for beginners and poor investors. 

Examples include the mini paddock pens, the trench pens, 

the moveable pens, 

Free range: This is a good method as it allows the snails 

free movement. The disadvantage in this method is that it 

is difficult to locate eggs, young snails and to keep out 

predators. 

PRECAUTIONS 

Before installation of snail farm facilities: 

(a) a good breeding foundation stock must be 

selected. 

(b) Active snails with no damages and weighing 

between 200 – 300g should be selected. 

(c) Ways of exposure to stress should be minimized. 

FOOD AND FEEDING 

Snails can be kept in groups of similar eat a huge variety of 

foods. In the wild they eat fresh or rotten leafy vegetations, 

an assortment of fruits like pawpaw, mangoes, banana. 

They also eat bread, cooked meat, chicken feeds, corn 

100

flakes or maize chaffs and mostly glabrous vegetables (e.g. 

Okra leaves, yam leaves and cassava leaves). The foods 

should remain in the cage for a reasonable length of time 

without rotting or casing smell. Rabbit pullets and layer 

mash are excellent foods. Foods should be abundant and 

available water should be copiously supplied. Locally 

snails can be fed with ripe fruits (paw paw, pears, banana 

etc) soft leaves (waterleaf, cabbage, green, paw paw 

leaves). They also can be fed scrape food like corn fufu, 

rice, cocoyams. Providing the snails a mixture of foods 

rather than one or two items, will enhance growth. 

Snails do not need salt and so the foods supplied then 

should be without salt. It is advisable to feed snails every 

day and to remove old foods. 

FARM MANAGEMENT 

The following are some of the daily activities in snail 

pens. 

Cleaning of feeders and drinkers 

Keeping pens clean 

Picking up and throwing away dead 

Picking of eggs 

Picking out snails with cracked shells 

Keeping records 

Checking the pens for any holes. 

101

Periodic Activities: 

Snails should be well mulched using dry leaves 

Snails should be regularly repaired 

Pens should be regularly repaired 

In due time snails should harvested and sold 

Pest should be controlled. 

Reproductive Facts: 

Snails are hermaphrodites (i.e. two sex organs per snail) 

Snails of the same size mate for 3 hours. 

Eggs are laid in batches. 

Eggs hatch after 14-21 days. 

Hatched snails mature after 3 months 

Snails of the same size are kept in one cage or box 

Snails can live up to 10 - 15 years depending on species 

All eggs picked are kept in hatching chambers 

Stocking density was expected to be 100 snails/m 2 ; 1000 

eggs/m 2 , 300 juvenile/m 2 . 

PEST MANAGEMENT 

No major diseases have been identified except the infection 

with Aeromonas. The major pests in snail farming are 

ground beetles, birds, birds including chirkon and ducks, 

black ants, millipedes, centipedes, light flies, frogs, snakes, 

lizards, human being and muscoid flies. The most 

important preventive measure is applying a mixture of 

engine oil, water and constructing cages with raised floors. 

The adult snails sometimes feed on young ones, so it is 

102

important that they are separated in predesignated 

chambers and to keep the entrance to the cages locked up. 

Keeping Records: 

Keeping records is an important aspect in snail farming to 

give an idea about the functioning of the farm at any one 

moment. It is important to keep record on number of eggs 

picked, number of installed, number of young ones, number 

of dead; quantity sold, feed purchased and material/inputs. 

Preparation of Snails: 

Snails are widely eaten as a delicacy particularly in West 

and Central Africa. They can be dressed with the shells, 

eaten as snail meat (fried); snail pepper soup, snail soya or 

vegetable/soup/stew. 

The heavy mucus secretion can be problematic but use of 

lime, Vinegar or Alum remove them very easily that after 

washing snails with these they can be cooked. The snails 

should be well cooked to avoid the toxicity noticed when 

improperly cooked snails are eaten. 

COST BENEFIT ANALYSIS OF SNAIL FARMING 

1 bucket of 400 snails costs = 20,000 

1 snail lays 15 eggs (Archachatina) therefore 400 snails 

will lay 400 x 15 = 6000 snails. 

Total number of snails will be 6000 + 400 mother snails 

= 6400 snails. 

103

Number of buckets of snail = 

6400 

= 16 buckets 

400 

selling at N20,000 a bucket means that 16 buckets will sell 

at 16 x 20,000 = 320,000.00. 

Profit = 320,000 – 20,000 = N300,000.00. 

From the above analysis, it shows that snail farming is a 

very profitable venture. 

This analysis was one with the low reproducing 

species Archachatina marginata. If it was done with a fast 

and high reproducing species Achatina Achatina that lays 

100 eggs a year the profit margin will be higher e.g. 

when you start with a bucket containing 600 snails 

but at N50.00 each 

= bucket will cost N30,000.00. 

At the egg production rate of 100egg/individual = 60,000 

eggs = 60,000 young. 

Total number of snails = 60,000 + 600 snails = 60,600 

60600 

Number of buckets = = 60 buckets selling at 

600 

N30,000.00 per bucket means that the 60 buckets will sell 

at 30,000 x 60 = N1,800.000.00. 

104

The profit = 1, 800,000 – 30,000 = N1,770,000.00 after 

one reproductive cycle. However in this species one 

expects a 15% mortality rate. 

In the quest for poverty alleviation, I propose that people of 

Nigeria should embrace snail farming as a means of 

achieving food security and economic empowerment 

especially for the rural poor in our world. 

Snails are slow growing, so farming them is not a way of 

making money quickly but with patience/good 

management and care it brings in substantial rewards in the 

long term. 

One of the advantages of snail farming is that feeding of 

snails is easy and relatively cheap as all the edible snails 

have a voracious appetite and can eat all manner of plants 

and plant parts. Captive snails have been fed on wild 

lettuce (Lactuca taraxacifolia) and a wide range of other 

leaves and ripe fruits including paw paw (Ajayi et al., 

(1978) listed 28 species of dicotyledonous plants and six 

species of monocotyledons eaten by A. marginata and 

Okafor (1990) reported that A. achatina preferred rough 

surfaced, hairy leaves e.g. Okro, paw paw and yam leaves. 

The Romans farmed snails for so many decades before the 

present civilization (Elmslie, 1982). Here in Africa, the 

feasibility of farming snails have been confirmed by the 

early 1970s (e.g. Ajayi, 1971; Plummer, 1975; Ajayi et al., 

1978; Hodasi, 1979 and Okafor, 1990). Currently in Ghana 

there is a major campaign to promote snail farming both as 

105

a back yard activity to supplement household income and 

protein supply. It is also a large scale commercial activity. 

The industry is growing rapidly and with adequate support 

both financial and technical, the industry has a high 

potential to change the life of both the rural and urban 

households. 

(e) OTHER ECONOMIC USES OF SNAILS 

(i) In Fashion Industries 

: The colour and luster of snail shells are exploited 

in decoration and for making jewelries. The 

operculum of prosobranchs is cut to make buttons. 

Cameos are produced using snail shells and a lot of 

artistic designs for home decorations are created 

using shells of gastropods especially marine 

gastropods. Pearls are iridescent because of the 

nacreous substance they are made from. The pearls 

can be black, pink, orange, gold or white. Black 

pearl are the most valuable of all pearls. Shape of 

pearls confers great value to them. For example 

round pearls are used to produce bangles, earring 

and necklaces. Those with irregular shapes are 

called “baraques” and are used in the fashion 

industries a lot. 

(ii) Aesthetics 

The shapes, colour and luster of shells are exploited 

by interior decorators and artists to produce amazing 

crafts, create designs and ornamental pins. Conchs 

and other larger and exotic shells can be polished for 

use as lamp busses or paper weights craftsmen 

fasten many kinds of snail shells together in the 

shape of dolls and animals in various types of 

106

designs that are very attractive and a sold 

exorbitantly. According to Eke (1998) many of the 

beautiful are collected, arranged and displayed in 

attractive manner for home and office decorations. 

Many people find shell collecting a fascinating 

hobby. They spend leisure times hunting and 

cleaning shells as well as mounting them in 

attractive displays. Today the collection and study of 

snail shells is a scientific discipline known as 

conchology. 

(iii) In Games 

In many African countries, the shells of Limicolaria 

spp are used for recreation e.g. locally called 

“Koso”. This game is played by two to four people 

in which people play in turns using the cylindrical 

shells cut at the end to make a cap on the ground. 

After making a successful gap, the player is entitled 

to use the shell to knock the others backside of the 

hand as a compensation for his skill. This game is 

played mainly by male children. 

(iv) Use as Money 

In the very old days before the modern civilization, 

shells of the Marine gastropods (Cypracea argus) 

where used as money. They are called cowries. No 

cowrie demonstrates the miracle of pattern 

production more than the well known, 4-inch long 

eyed cowries of the Southwest Pacific whose fleshy 

mantle produce a uniquely characteristic colouration 

and pattern. The shells of the young cowries are 

thin, without shelly teeth and without distinctive 

colour patterns. These are used as money. When 

107

they age they develop shell teeth, the shells become 

larger and thicker. 

There is also the Golden cowrie (cypraea 

auranitium) which has been greatly sought after by 

collectors for many centuries. Its popularity is due to 

its relative rarity, its beautiful glistering orange 

colouration, and because of its historical use as a 

symbol of chieftainship in the Fiji Islands, South of 

Japan; through out the Philippines and Solomons to 

Fiji. 

(v) Other Scientific and economic Uses 

The Phoenicians and Romans made a purple dye 

from some sea snails (e.g. Murex). The believed that 

cloth coloured with this dye was more valuable than 

gold. 

Wampum, which consisted of beads made from 

shells, was used by the Indians to decorate garments 

and also to keep records. Most wampums were made 

into necklaces or belts. In ancient days, Indian 

wampum were used as currency. 

Scientists use snail shells in their researches. For 

examples, Atomic energy researchers expose shells 

to atomic rays to test the effects of radiation. 

Oil prospectors search for certain kinds of fossil 

shells in the deserts. These shells show that the area 

was an ocean bed many years before now. Large oil 

pools were found in many of these ocean beds as it 

is today in the Middle East areas of the world. 

Man often release the snails into the environment to 

act as predators of other snail e.g. Marisa 

108

cornuarietis or of flatworms as biological control 

agents. 

The snails have a voracious appetite. Some people 

introduce the snails in their rice and maize farms to 

eat up the weeds in their farms. The dangers in this 

however, are that the introduced snails can in a short 

time, reach such enormous numbers and become 

serious conservation problem, or eat up native plant 

species modifying the habitat and they out compete 

native snails. 

Finally the snails can be used as pets, can be used to 

teach about native fauna, and for other educational 

purposes on a state by state basis, as nature facilities 

in teaching biodiversity and for physiological and 

drug research. 

6. CONTROL OF SNAILS 

Snails are an important part of many ecosystems 

constituting a major portion of the total animal 

biomass. They are food for other animals but some 

snails are predators themselves, many consume dead 

and dying plant material and therefore they are 

important in the cycling of nutrients through the 

ecosystems. Other species of snails carry diseases 

such as schistosomiasis, angiostrongyliasis, 

dicrocoeliasis, etc that infect man while some 

species have become crop pests. They are also 

incriminated in habitat destruction and modification. 

109

Against this background, efforts have been made 

over the years to control or even eradicate snail 

population both on land and in the freshwater 

habitats. 

The snails often thrive in forest edges, in modified 

forests and plantations as well as natural forest and 

freshwater ecosystems. Wherever they occur, they 

keep to the hot humid areas. The snails are killed by 

sunshine. They remain active at a temperature range 

of 9 0 C to 25 0 C by hibernation and 30 0 C by 

aestivation. In agriculture the Africa land snail is 

regarded as one of the worst snail pests as they 

consume large volumes of native plants prompting 

the introduction of predatory species e.g. Bufo 

mannus (the invasive toad) in Japan or some species 

of red crabs or even some predacious snails like 

Euglandina prey on underwater snail species. There 

is even a more voracious and indiscriminate predator 

used called Platydemus sp. 

The most important reason for snail control is hinged on 

the fact that snails serve as vectors for several pathogens, 

and parasites. Most especially important for land snails are 

that they transmit the worm Angiostrongylus catonensis 

responsible for eosinophilic meningo – encephalistis in 

man as well as the bacterium Aeromonas hydrophila. It was 

noted in the turn of the 20 th Century that the parasites 

carried by the snails are usually transmitted to man through 

the consumption of raw or improperly cooked snails. Such 

disease as Eosinophilic radiculomyeloencephalitis can be 

contracted by this route. This resulted in many countries 

instituting quarantine measures to intercept snails. 

110

In few location of the world, snails have been successfully 

eradicated e.g. U.S.A. and Queensland (Australia). In these 

areas the control costs can range from US$60,000 for a 7month 

procedure to over US$700,000 for the eradication 

for a long period. Hand collection plays a major role in 

eradication; this is usually followed subsequent destruction. 

The most pragmatic approach to control of land snails is 

the use of pesticides (mo,lluscicides) such as metaldehyde, 

methiocarb (mesurol), iron phosphate, coconut oil soap, 

copper sulphate slurry, Bordeaux mixture, metallic copper 

strips or foil. 

In freshwater snail control, chemical or physical measures 

have been found to be effective in reducing or eliminating 

snail populations, thus affecting parasite transmission and 

so snail control has been found to play a significant role in 

morbidity control programmes. Blanket mollusciciding has 

been suggested to be cost effective in irrigation schemes. In 

such diseases like schistosomiasis whose transmission is 

focal & seasonal, focal mollusciciding at easily identified 

transmission sites is the method of choice. 

Environmental snail control measure include filling or 

draining of the marginal areas, concrete living of all the 

integration of chemical control and removal of vegetation 

are advocated. Bayluscide is the current molluscicide of 

choice. 

7 CONCLUSION 

I have in this lecture, tried to give an overview of the 

intricate relationships between man and snails. I started 

with the systematics and biology of the snails to the various 

snail products that man has learnt to use to his benefits. I 

111

tried to show the various roles snails and snail products 

play in the dynamics of human life especially the various 

ways man has benefited and the ways he must develop to 

get more out of the relationship with the snails. It is 

important to note that while this effort does not pretend to 

present a comprehensive treatment of snails, it tried to 

present the facts that man and snails are inextricably related 

in certain aspects of human endeavours and also tried to 

show that the snails make up a high proportion of species 

and biomass in the human environment that can be 

exploited especially in the tropics. It tried to bring out the 

great diversity of the snails and their ecological adaptations 

ranging from morphological traits, special physiological 

and metabolic reactions coupled with their variability and 

ecological relevance. In all, I tried to present the various 

ways man had processed snails and the many ways snails 

warmed their ways into the dynamics of human existence. 

Furthermore I tried to give a comprehensive taxonomic 

treatment of the edible snails at the generic levels which 

will be of immense help to researchers interested in their 

studies. 

In treating snails as food I tried briefly to introduce the 

emerging interdisciplinary field of snail farming which is 

production. People involved in developing sustainable 

ways of rearing snails as a commodity, that could be 

managed and conserved, to improve human food security 

(especially for protein and mineral supplementation) will 

find this little effort interesting. 

I highlighted the fact that many people are upset with snails 

and that farmers get angry when snails eat their plants and 

crops. This shows snails as pests & that they cause serious 

112

damages to crops. So, they must be eradicated or at best be 

controlled. 

In all, I managed to give the good, the bad and the ugly of 

man-snail relationships that should be of great interest to 

people with varied backgrounds with the mind to search 

for the micro and macro perspectives, linking the welfare 

criteria of man with issues of technical progress, enhancing 

social security in areas of limited resources and policy 

implications for families and communities’ income 

generation in the tropics Unfortunately, in these areas, 

endemic diseases, malnutrition and poverty are acute 

human problems. 

It is my humble submission that more facts and experiences 

should be accumulated to help us in better understanding 

more the roles of the snails in education, training, research 

and product development for the use and for the benefits of 

man. 

Thank you. 

ACKNOWLEDGEMENT 

The vice chancellor Sir, I crave your indulgence at this 

point to acknowledge in Public that God the Alpha and 

Omega had been my support up till now in such a palpable 

manner that all that know me ascribe to Him the glory for 

my life, my education and all that concerns me. I am also 

indebted to the Vice Chancellor for this golden opportunity 

given me to give the lecture and for other innumerable 

favours and confidences. 

I thank my friend Prof O. U. Njodu. and his committee 

members for granting me this opportunity to give this 

lecture with a lot of support and understanding. I am 

113

greatly indebted to my wife Lady Uche Okafor for her 

devotion and tremendous support. I appreciate the 

contributions of my children Nchekwube, Chijindu, 

Chinazam, Nkiruka, and Chiamaka to the successful 

conclusion of the writing that culminated to this lecture. 

As I started this journey in academics, it was my father late 

Mr Eleazar Udeze Okafor who bore all the pains of my 

sustenance and so I salute his courage. My mother Emily 

Enuzo Okafor was always there to feed and nourish me; 

and to provide all domestic needs of mine. My late uncles, 

Ernest, Wilson, Cyprain, Benson, Samuel and Christopher 

I never forget. They believed so much that I was a star and 

they never let any. opportunity to pass by with out giving 

monetary and advisory supports. I am sincerely grateful to 

them. 

At the University, I am happy and will continue to show 

gratitude to Prof. A. B. C Nwosu who was always there to 

lead me on the right parts and infused the right energy into 

me. I will always remember his contribution to my growth. 

The same goes for uncle Joe Ezigbo,they were so helpful. 

My post Graduate supervisor is one in a million. When I 

look back at his ever towering figure, I continue to thank 

God that he brought this man to mentor and teach me. I am 

talking about Prof. Anya Oko Anya. I will eternally be 

grateful to him and his wife our mummy Inyang. 

Finally I am grateful to all my colleagues and friends, who 

are always there in my times of need, I mean people like 

OK, Dyke ,Carl, CIA, VCE, JEE, NSO and Others I plead 

for God’s blessing on you all. I will not forget my in-laws 

for their concern and support. 

114

115

REFERENCES 

1. Adekoju-John, E. O. and Abolarin, M. O (1986). Status 

of human schistosomiasis on the eastern side of Kainji 

lakeof Nigeria. East African Medical Journal, 63, 

469-470. 

2. Adeola, M. O. (1992). Importance of wild animals and 

their parts in the culture, religious festivals and 

traditional medicine of Nigeria. 

Environmental conservation, 19, 125-134. 

3. Adeola, M. O and Decker, E. (1982). Wild life 

utilization in rural Nigeria. In clers, B. D. (ed) proc. of 

the international symposium and conference on wild 

life management in sub sharan African, 6-13 October, 

1987, Harare, Zimbabwe, pp512-21. 

4. Adewunmi, C. O., Furu, P., Christensen, N. O., 

Marquis, B.B and Fagbola, M. (1990) Endemicity 

and seasonality of transmission of human 

schistosomiasis in 11e ife South weatern Nigeria. 

Tropical medicine and parasitology, 41, 443-445. 

5. Afolayan, T. A. (1980). A synopsis of wild life 

conservation in Nigeria. 

Environmental conservation, 7,207-217. 

6. Afolayan, T. A. and Ajayi S.S.(1983). Fifty years of 

Nigerian wild life resources. 

116

The Nigerian Field, 44 (4), 130-144. 

7. Ajayi S.S. (1971). Wild life as a source of protein in 

Nigeria some priorities for development. 

The Nigerian field, 36,(3), 115-127. 

8. Ajayi S.S (1973). Wild life management in the national 

economy. 

Nigerian Journal of Forestry, 3 (1), 26-30. 

9. Ajayi, S.S., Jewett O. O., Moriarty C. and Awesu, M. 

O. (1978). Observations on the biology and 

nutritive value of the giant African land snails 

Archachatina Marginata 

African Journal of Ecology, 16, 85-95. 

10. Anadu P. A. (1987). Progress in the conservation of 

Nigeria’s wild life. 

Biological conservation, 41, 237-251. 

11. Akinnusi, O. A. (1998). Practical approach to backyard 

snail farming. Nig.J. Anim. Prod., 25, (1-2), 193- 

197. 

12. Anosike J. C., Okafor, F. C., and Onwuliri C. E. O. 

(1992). The prevalence of Urinary schistosomiasis in 

Toro L. G. A. of Buachi State Nigeria. 

117

Helmithologia, 29,177-199. 

13. ANON (1986). Molluscs in Medicine. Carefel Plulip 

(ed) Shell News, 8 (2), p.9. 

14. Anstey, S. (1991).Wildlife utilization in Liberia, Report 

of a survey undertaken for the world wide fund for 

Nature. Gland, Switzerland. Unpubl. 

15. Anya, A. O. and Okafor F. C. (1986). Prevalence of 

urinary schistosomiasis in anambra State Nigeria. 

Bull. de L’IFAN, 46, 321-32. 

16. Anya, A. O. ed Okafor, F. C. (1991a). The factors 

affecting the abundance of Bulinus globosus in 

freshwater systems of Anambra State, Nigeria. 

Proceeding of the Nig. Academy of Sciences, 9, 11- 

22. 

17. Anya, A. O. and Okafor, F. C. (1991b). Field age 

structure, developmental biology and reproduction 

of Bulinus globosus and factors affecting its growth and 

reproduction. 

Tropical Ecology, 32 (1), 69-85. 

18. Asibey, E. O. A (1986). Wildlife and Food security. 

FAO Forestry Department Report, Rome. 

118

19. Asibey, E. O. A. and child, G. (1990). Wildlife 

management for rural development in sub-Saharan 

African 

Unasylva, 41, 3-10. 

20. Avagnina, G. (1982). New methods for rearing edible 

snails 

Informative Zootecnics, 29 (18), p.85 

21. Azugo, W. I. (2008). Ecology of gastropod molluscs in 

Obutu lake, Anambra State Nigeria. 

PhD. Thesis, University of Nigeria Nsukka, 297pp. 

22. Baratou, B. (1988). Raising snails for food. 

Calistagu, Califormia Illumination press, pp 38-40. 

23. Baur, B. (1992). Cannibalism in gastropods. In 

Cannibalism, Ecology and Evolution among diverse 

Taxa (eds M. A. Elgar and crespi, B. J.) Oxford 

University press, Oxford pp 102-127. 

24. Baur, B. and Baur, A. (1992) Effects of courtship and 

repeated copulation on egg production in the 

simultaneously reared hermaphroditic land snails. 

Arianta arbustorum. 

Invert. Reprocuction and Development, 23 (1), 201- 

206. 

119

25. Betterton C. and fryer, J. E. (1982). Schistosoma 

haematobium in Northern Nigeria a complex of 

snails hosts and parasitic strains. Parasitology, 85 (2), 

supplxx11. 

26. Bequaert, J. C. (1950). Studies in Achatininae, a group 

of African land snails. 

Bull. Mus. Comp. Zool., Harares, 105, 1-216. 

27. Calow, P. (1970). Studies on the natural diet of 

Lymnaea pereger Obtusa (kobelt) and its possible 

ecological implications. Proc. Malacol. Soc. 

Lond., 39, 203-215 

28. Cavallo passerini M. G. (1998). Practical studies and 

application on open air treeding to completes life cycle 

of Helix pomatia 

Elicicoltura, April, 1998, P.12. 

29. Cavallaro, R. and Ravera, O. (1966). Biological 

indicator of Manganese-54 contamination in 

terrestrial environments. 

Nature (loud), 209,259. 

30. Chen, M. G. and Feng, Z. (1999). Schistosomiasis 

control in the people’s Republic of china. 

Parasitol. Int., 48, 11-19. 

31. Cowper, S G. (1973). Schistosomiasis in Nigeria. 

Ann. Trop. Med. Parasite., 57, 307-322. 

120

32. Dei, G. J. S. (1989). Hunting and gathering in a 

Ghanaian rain forest community Ecology of Food 

and Nutrition, 25, 29-49. 

33. de vanfleury, A. G., and Borgo, R. (2001).Invertebrate 

reproduction and development., 40 (2-3), 217- 

226. 

34. de-Grisse, A. and Mededelingen van (1990). 

Oviposition and egg incubation in artificial 

conditions by Helix aspersa Mullor Fac. Landbouw. 

Rijksuniv. Gent, 65, 35-46. 

35. Dimitriadis, V. K. (2001). Structure and function of the 

digestive system in stylommatophora. In: The 

Biology of Terrestrial molluser (ed G. M. Barker), C 

A B Informational, walling ford , pp 237-257. 

36. Davis P. R., van schagen, J. J., Widmer, M. A., craven, 

T. J. (1996). Slug and snails pasts in Agiculture. 

Proc. Of a symposium held at University of Kent, 

Canterbury, U. K; 24- 26 sept.,1996. 

37. Ebomoyi E. S. (1988) Nutritional beliefs among rural 

Nigerian mothers. 

Ecology of Food and Nutrition, 22, 43-52. 

38.Egonwan, R. I. (1992). Food selection in the land snails 

Limicolaria Flammea (muller) (pulmonata: Achatinildae) 

121

J. Molluscan Studies, 58, 49-55. 

39. Egonwan, R.I. (2004). Maturation timing in the Afric 

land snail Archeehatina marginata ovum (pfeifferi) and 

Limixolaria Flammea (muller)(pulmonata: 

Achatinidae) 

Invert Reprod. And Dev., 461, 159-172. 

40. Egonmwan, R. I. (2007). Food utilization in a 

laboratory colony of the giant African land snail 

Archachatina marginata 

Turk. J. of zoology, 37, 265-270. 

41. Elmslie, L.J. (1982). Snails and snail farming . 

World Animal Review, 41, 20-26 

42. Eltringham, S. K., (1984). Wildlife resources and 

economic development. John wiley and sons New York, 

U.S.A, 325pp. 

43. FAO (1986). Natural resources and the human 

environment for food and agriculture. F A O, 

Rome. 

44. Gomot, A. (1998). Biochemical composition of Helix 

snails: Influence of genetic and physiological 

factors. 

122

J. moll. Studies, 64 (2), 173-181. 

45. Grisse, A., de Defloor, J., Vercanteren, F., King . J. M. 

and Heath, B. R. (1975). Game domestication for 

animal production in African world animal Rev., 16, 23- 

30. 

Mededelingen F., (1996). Influence of mixing different 

soil types (chalk, sand, leaf moued, peat) with 

feed on the growth of the edible snail Helix aspersa 

maxima, landbouw. Toeg. Biologische Weternsc, Univ 

Gent., 61 (1), 129-139. 

45b. Grisse A. (1994). Snail breeding, from hobby to 

profession. De source Geat. (Belgium), 234pp. 

46. Hodasi J. K. M. (1995). Effect of different types of foods 

on the growth of Achatina achatina. In Abstract of the 

12 th Malacological congress, Vigo, 488-489. 

47. Hodasi, J. K. M. (1984). Some observation on the 

edible giant land snails of West Africa. 

World Animal Review, 52, 24-28. 

48. Hodasi J. k. M. (1989). The potential for snail farming 

in West Africa. Slugs, and snails in world Agriculture, 

41, 27-31. 

123

49. Hopocraft D. and Arman, P. (1971). Preliminary 

records on comparative productivity of wild and 

domestic animals. Appendix 11. Ntional Report on 

the human enviroment in Kenya, 102 pp. 

50. Iheagwam, E. U.and Okafor, F. C. (1984). The biology, 

life tables and intrinsic rate of natural increase of 

Bulinus (physopsis) globosus (mowlet) and 

hymnaes ntalensis (known Gastropoda, pumonata) snail 

informodiatehosts of schiztosoma haematobium and 

fysciolagigaatica respectively in southerstern 

Nigeria Bietr. Trop. Land wist vetrinanod. 22 

(A).429-434. 

51. Imevbove E. A. and Ajayi, S. S (1992). Food 

preferences of the giant African land snails 

(Archalhatina margiata) in captivity. African J. of 

Ecology, 31 (3) 265-267. 

52. Ireland, M. P. (1970). Distribution of essential and toxic 

metals in the terrestrial gastropod, Arionater. 

Environmental Pollution, 20, 271-378. 

53. Jardin C. (1970). Lists of foods used in African. 

Nutritional Information Document, series 2, FAO, 

Rome 

55. Liu, Y. (1983). Progress on the study of medical 

mollscs during the past 32 years in New china. 

Trans. China Soc. Malacol., 1, 197-207. 

124

56. Lux moore, R. (1985). Game farming in South African 

as a force in conservation. 

Oryx, 19, 225-231. 

57.Makombe, K. E. (1993). Sharing the land wildlife, 

people and development in Africa. 

IUCN Regional office for southern Africa, 36 pp. 

58. Malak, E. A. (1982) Snail transmitted parasite diseases. 

Med. Journal, 6 (4), 153-163. 

59. Marigimez, J. A., Angulo, E., and saez, Y. (1986). 

Feeding and growth responses to copper, zinc, 

mercury, a lead in Environmental gastropod Arion ater 

(linne) 

Journal of Molluscan Studies, 52, 68-78. 

60. Martin, G. H. G. (1985). Bushmeat in Nigeria as a 

natural resource with environmental implications. 

Environmental Conservation, 10, 125-132. 

61. Martin, G. H. G. (1985). West Africa: Carcass 

composition and palatability of some wild animals 

commonly used as food. World Anim. Rev; 53, 40- 44. 

125

62. Mason, C. F. (1970). Food, feeding rates and 

assimilation in woodland snails. 

Oecologia, 4, 358-373. 

63. Mead, A. R. (1957). Achatina fudica enters the 

economy. (A. Burges and F. Raw eds) 

Academic press, London. Pp413-433. 

64. Muir, K. (1989). The potential role of indigenous 

resources in the oconomic development of and 

environments in sub-saharan Africa the case of 

wildlife utilization in Zimbabwe. 

Seciety and Natural Resources, 2, 307-318. 

65. Newell, P. F. (1967). Mollusca in soil Biology (A. 

Burges and F. Raw eds). Academic press lands 

pp413-433. 

66. Nisbet, R. H. (1974). The life of Achatinidae in 

London. Pro. Soc Mollusc. Studie. London, 41, 171- 

183. 

67. Odo, S. (1995). Epidemiology of urinary 

schistosomiasis in Benue State, Nigeria. PhD. 

Thesis, University of Nigeria, Nsukka, 280pp. 

68. Okafor, F. C. (2001). Edible land sail: A manual of 

breeding management of Achatima achatina. 

Simarch Publizahas, Lagos 72pp. 

126

69. Okafor, F. C. (1989). Consumption and assimilation of 

food in Achatina A. achatina (L). Tropical Ecology, 

20(1), 52-57. 

70. Okafor, F. C. (1989b). Distribution of Fresh water 

gastropods in the River Niger and Cross River basins of 

southeastern Nigeria with reference to their 

trematode infections. 

Bietr Trop landwirt. Veterinamed., 28, 207-212. 

71. Okafor F. C. (1990a). On the effects of Ivermectin on 

snails of Medical and Veterinary importance 

Angwe. Parasitol., 31, 65-68. 

72. Okafor F. C. (1990b). Schistosoma haematobium 

cercarriage transmission patterns in freshwater 

systems of Anambra State, Nigeria. 

Angwe. Parasitol., 31, 159-166. 

73. Okafor, F. C. (1991). The effects of temperature on 

embryogenic development and reproduction of the 

freshwater snails Bulinus globosus (Morelet) and 

Lymnaea natalensis (Kraus).(Gastropoda: Pulmonata). 

Nig. J. Aquatic Sci., 6, 7-11. 

74. Okafor, F. C. (1991). Host spectrum in the transmission 

of Schistosoma haematobium in southeastern Nigeria. 

Rivista Parasit., 2, 337-344. 

127

75. Okafor, F. C. and Obiezue RNN (2004). Malacological 

survey of the Anambra River basin in Anambra 

State, Nigeria. 

J. Bioresources and Biotechnology, 2(1), 29-28. 

76. Ngang I and Okafor F. C. (2004). Effect of permethrin 

on survival and reproduction of Buliniis globosus 

(morelet,1868) and Bulinus truncatus (Audoin, 

1872) 

Anim. Res. Int., 1(2), 110-112. 

77. Okafor F. C and Ngang (2004). Freshwater snails of 

Nkalagu Eastern Nigeria: Observations on some 

demographic aspects of the schistosome 

transmitting buliniids. 

Anim. Res. Int., 1(2), 120-124. 

78. Osemeabo, G. J. (1992). Effects of land use and 

collection on the decline of African giant snails in 

Nigeria. 

Environmental conservation, 19, 153-159. 

79. Olufokunbi, B., Phillips, E. O., Omidiji, J. O, Ogbonna, 

U. O., Makinde, H. T. and Apansile, O. j. (1989). 

The economics of commercial domestication of the 

African giant land snail Archachatina (calachatina) 

marginata (swainson) in Nigeria. In the series 

analytic, “slug and snails in Agriculture”. 

128

Proc. Symposium organized by the British crop 

protection council, April 10-12, 1989. University 

of Surray, Guild ford, England series No. 41, 41- 88. 

Thorton Heath, England. 

80. Ozumba, N. A., Christensen, N. Nwosu, A. B. C and 

Nwaorgu, O. C. (1989). Endemicity, focacity of 

transmission of human schistosomiasis in Aruagunze 

Village, eastern Nigeria. 

Journal of Helminthology, 63, 206-212. 

81. Owen, D. F. (1975). A remarkable example of 

polymorphism in an African land snail. 

Bull. De L’IFAN, 37, 771-774. 

82. Plummer, J. M. (1975). Observations on the 

reproduction, growth and longevity of a laboratory 

colony of Archachatina (calachatina) marginata 

(Swainson) subspecies Ovum. Proc. Malacol. Soc. 

London, 41, 395-403. 

83. Russel-Hunter, W. D., Meadows R. T., Appley, N. I. 

And Brukey, A. J. (1968). On the use of a wet 

oxidation method for estimating total organic 

carbon in molluse growth studies. 

Proc. Malacol. Soc., London., 40. 407-12. 

129

84. Sanz-Sample layo, M. R., Fonolla, J. and Extremera, F. 

G. (1991). Factors affecting food intake, growth 

and protein utilization in the Helix aspersa snails: 

Protein content of diet and animal age. 

Laboratory Animals, 25(4), 291-300. 

85. Sheldon, C. (1988). Raising snails: special reference 

briefs. National Agricultural library SRB88-04. 

Beltsville, Maryland. USDA, pp212-230. 

86. Solem, A. (1974). The shell makers: Introducing 

mollusce. 2 nd Edition. Blackwell scientific 

publications, London, pp 210-230. 

87. Taylor, T. W. (1900). Monograph of the land and fresh 

water molluscs of the British 1sles: I. Structural and 

General. Leeds, Taylor and Bros. 454 pp. 

88. Tucker, R. A. (1976). Sea Shells. Transworld Publishers 

Ltd, Verona, London. 95 pp. 

89. Wilbury, K. M. (1983). The Mollusca Vol. I. Academic 

press, New York, London, pp 180-210. 

90. Webbe G. (1987). The use of molluscicides in the 

control of human trematode infections. 

In “The Toxicology of molluscicides intervention”. 

Encyclopedia of pharmacology and Therapentics, 

Section D125. pergamon press, oxford. Pp1-11. 

91. Well, P. B. (1948). Some notes on the African giant 

snails Achatina fulica: on its economic significance. 

130

Chronicle Nautilus Batavia, 104,278-285. 

APPENDIX 1: 

131

DESCRIPTION OF SOME OF THE 

GASTROPODA (AFTER, Yuri Yashin,2001) 

Achatina balteata Reeve,1849 

Shell olive-yellow, yellowish-brown, chestnut 

with or without blotches or streaks. 

Length 100-148 mm and width 52-73 mm. 

The shell has been used as money in 

Angola(cut into disks)and the Congo(cut 

length-wise). 

In Upper-Guinea, Cameroon to Central Angola, 

Sierra Leone and Gambia. 

132

Achatina fulicaBowdich,1822 

Shell size is very variable, depending on 

locality, from 72-171 mm in length to 37.5-81 

mm in width,dark brown with lighter vertical 

bands. 

This species is both a favourite pet and serious 

pest. 

Originally in East-Africa,but imported in India 

and the Pacific. 

According to Bequaert(1950)there are five 

subspecies: 

Achatina fulica fulica 

Achatina fulica hamillei: larger, pale olivegold 

yellow with chestnut streaks. 

Achatina fulica coloba: yellowish-red 

brown, & streaked. 

133

Achatina fulica rodatzi:olive-yellow with 

dark yellow streaks, pale body 

Achatina fulica castanea: above the 

periphery dark buff,below light brown. 

Another subspecies is A.f. umbilicata, this has 

a very convex body whorl. 

Achatina iostoma Pfeiffer,1852 

About 13cm,light brownish with a granular 

surface. 

In Cameroon. 

134

Achatina immaculata Lamarck,1822 

Shell:Thick and large,shape very 

variable,columella and inside of lip pink. 

Apex smooth. 

Color is whitish,buff or light brown,with darker 

brown axial stripes which are relatively straight 

compared to other Achatina species. 

Achatina panthera Ferussac, 1832 is now to be 

believed As a narrow variety of A. immaculata. 

Habitat: Coastal lowlands, dune forests, 

gardens, valley thickets and savanna 

woodlands. 

Distribution:East-Africa. 

Achatina iredalei Preston, 1910 

135

Shell thin, semi-transparent, lemon yellow, 

about 70-100 mm. 

This species is one of two (the other one being 

Cochlitoma zebra) Achatinids to give birth to 

live young. 

Achatina reticulata Pfeiffer,1845 

Shell yellowish white to reddish brown with 

vertical markings,on the body whorl are 

spiral lines and vertical welts.The periostracum 

is very thin and usually lost in 

adult specimens. 

The head and tentacles are dark brown,with a 

dark brown band running down the center 

towards the shell. 

The eyes and tips of the tentacles and rest of 

the body are pale 

yellowish brown. 

Length 160 mm and width 75 mm with 8-10 

whorls. 

In Zanzibar. 

136

Achatina stuhlmanni von Martens,1892 

About 10cm. 

In Uganda. 

Achatina schweinfurthi von Martens,1873 

About 14cm,light brownish with lightning 

darker stripes. 

In East-Africa. 

137

Metachatina kraussi Pfeiffer,1846 

Shell:Large and thick, lip thickened, columella 

not truncated as in other Achatinids. However 

young snails do have a truncated columella. 

Color whitish with brown streaks on the 

apex,columella and inside of the lip dark brown 

to purplish brown. 

Length up to 160 mm. 

The animal has a dark grey head and tentacles 

with a broad band running towards the 

shell,the sides are paler while the foot is 

whitish grey. 

Habitat: Dune, coastal lowland forest,valley 

thicket,savanna woodland. 

Distribution: Eastern South-Africa; KwaZulu 

Natal north to Mozambique,inland towards 

Ithala,the Lebombo 

Mountains,Kranskop,Glencoe,the Vryheid 

region,south to Ifafa. 

Genus Columna 

Columna columna(Müller,1774): São Tomé and 

Principe 

138

Columna leai(Tryon, 1866) : São Tomé and 

Principe 

a b 

a. Columna leai Tryon,1866 . 

b. Columna columna Müller,1774 

139

APPENDIX II 

SHELLS OF NIGERIAN SNAILS (After Okafor 

F.C., 2009) 

Shells of Potadoma Spp. 

Shells of Lanistes ovum 

140

Shells of Gyraulus costulatus 

141

Adults of Achatina achatina 

142

Shells of Biomphalaria pfeifferi 

143

144

Shells of Lanistes varicus and operculum 

145

Adults of Achatina balteata 

146

147

APPENDIX 111: PICTURES OF AFRICAN COMMON 

SPECIES 

A mixture of Buliniid shells 

Achatina panthera 

148

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Achatina iredalei 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

149

Courtesy of 

Yurii Yashin 

Courtesy of 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Achatina glutinosa 

Courtesy of 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Courtesy of 

Yurii Yashin 

Courtesy of Courtesy 

150

Yurii Yashin Yurii Yashin Yurii Yashin Yurii Yash 

Courtesy of 

Beth 

Courtesy of 

Yurii Yashin 

Courtesy of 

Daniel Israelsson 

Courtesy of 

Achatina immaculata 

Courtesy of 

Yurii Yashin 

Courtesy of 

Daniel Israelsson 

Courtesy of 

Courtesy of 

Emmanuelle 

Bresci 

151

Courtesy of 

Sarah Houghton 

Courtesy of 

arah Houghton 

Emmanuelle Bresci Emmanuelle Bresci 

Courtesy of 


Courtesy of 


Achatina fulica 

Courtesy of 


Courtesy of 


Courtesy of 


Courtesy of 

152

153

THE VARIED ROLES OF SNAILS - National Universities Commission

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?