Int.J.Curr.Microbiol.App.Sci (2020) 9(6): 2170-2177
International Journal of Current Microbiology and Applied Sciences
ISSN: 2319-7706 Volume 9 Number 6 (2020)
Journal homepage: http://www.ijcmas.com
Original Research Article
https://doi.org/10.20546/ijcmas.2020.906.265
Embryonic Development of Discus,
Symphysodon aequifasciatus Pellegrin, 1904 in Indian Condition
Sambid Swain1,2, Paramita Banerjee Sawant1*, J. K. Sundaray3,
E. M. Chhandaprajnadarsini4 and Milind B. Katare1
1
2
ICAR-Central Institute of Fisheries Education, Mumbai, India
Centurion University of Technology and Management, Odisha, India
3
ICAR- Central Institute of Freshwater Aquaculture, India
4
ICAR-Central Marine Fisheries Research Institute, Kochi, India
*Corresponding author
ABSTRACT
Keywords
Embryology,
Hatching,
Development,
Discus
Article Info
Accepted:
18 May 2020
Available Online:
10 June 2020
The experiment was conducted to investigate the embryonic development of discus
(Symphysodon aequifasiatus) and determine the time required for major egg
developmental stages and hatching. Regular observations were made using optical
microscope and the images were recorded using a digital camera attached to the
microscope. Important water quality parameters were kept optimal for the hatching of
discus eggs. Newly laid eggs were oval-shaped and yellow in colour with an average
diameter of 1.37 ± 0.14 mm. The embryonic development of fertilized eggs was divided
into 16 stages and the development of each stage was recorded in times lapse. The result
revealed that cleavage occurred after 1hr after fertilization followed by development of
blastula and gastrula at 20.5 hr and 24 hr after fertilization respectively. The period of
organogenesis started with the formation of embryonic notochord from 37.5 hrs after
fertilization. The appearance of a defined head and tail of the embryo with 19 somites was
observed at 40.0 hrs after fertilization, whereas heart beat along with blood circulation
appeared after 55.5 hrs after fertilization. The eggs hatched after 69.06 hr after
fertilization.
Introduction
Discus (Symphysodon aequifasciatus), a
cichlid are mostly found in unpopulated small
stream and creek of the Amazonian basin has
high marketability due to its attractive colour
is considered as a high-value ornamental fish
(Santos et al., 2006, Wattley, 1991). It
possesses a complex and unique reproductive
behavior which involves establishment of
breeding territories by the male, selection of
mate for pair formation, selection of suitable
site or substrate for egg laying and subsequent
spawning (Chellappa et al., 2005).
One of the rare characteristics of discus
breeding is discus brooder shows parental
care and secretes nutritious mucus from its
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epidermis for feeding of hatchlings (Chong et
al., 2005). For easy understanding of biology
of a species the knowledge of embryology can
be considered indispensable tool. Inadequate
knowledge about the early life stage of a fish
can affect its economic sustainability as it has
a major impact on the zoo-technical
performance and the survival of the fish.
The knowledge of embryology can not only
helpful in locating the spawning areas but also
identifying the physiological requirements of
the fish which can aid to improvement in
culture operation and conservation of the
icthytofauna (Godinho et al., 2003; Anjos and
Anjos, 2006). For determination of viability
and quality of a teleost egg, observing the
early developmental stage of the egg is
considered as a practical and reliable method
(Senhorine, 1993; Vallin and Nissling, 1998).
The developmental period of a fish can be
defined as the period in which the developing
individual entirely depends on the endonutrients from the yolk of the egg (Liew et al.,
2006). The developmental period of the fish
depends on the fish species and the
environmental conditions. The embryonic
phase of a fish which begins with the
successful fertilization of the egg and its
duration includes the time interval between
fertilization and eclosion (Jobling , 2002).For
proper understanding the embryonic phase of
fishes is divided into two phases.
The first phase is the cleavage phase in which
first cell division occurs with the appearance
of neural plates and in the second phase
embryo becomes noticeable as a vertebrate
(Moyle and Cech, 2004).Since a detail
embryonic study of discus fish (S.
aequifasciatus) is scares, the current
experiment aims to provide the information
about the early developmental stages which
will be helpful for the fish breeders and
researcher.
Materials and Methods
Discus brooders (103.4 ± 9.32g) were
procured from the local ornamental fish
traders in Mumbai, Maharashtra, India and
were transferred to discus rearing facility of
ICAR-Central institute of fisheries education,
Mumbai. These were acclimatized to captive
condition in 1000 l glass aquaria fitted with
power filter and heater along with adequate
aeration facility for 15 days. Fishes were fed
with artificial commercial diet comprising of
pellet feed and moist feed (Minced Chicken,
Beef Liver) @ 6% and 8% of their body
weight respectively every alternate day. Pre
spawning behaviour was observed during this
period, after which the pairs were transferred
to 100 l breeding tanks for initiating natural
spawning. The breeding tanks were also
equipped with power filter, thermostat and
have aeration facilities for maintaining ideal
condition for breeding. PVC tubes of 30 cm in
length were placed in the tank as substrates.
The adhesive eggs of discus were found
attached to the substrate which was latter
scrapped using scrapples and were counted.
In order to observe the developmental stage
following procedure was followed i)
Observation was made every 30 min, 60
mins,90 min from the fertilization till the end
of the gastrula phase, start of organogenesis
till emergence of heart and emergence of
heart till hatching respectively using olympus
SZX16 strereozoom microscope ( 15X
magnification) which was photographed
digitally by a camera attached the microscope.
For each observation one third of the total
number of egg was selected randomly which
were latter placed in a petri-disc and were
observed under the microscope. The eggs
were analyzed for quality and those
unfertilized and had fungal infection were
discarded. The embryonic stages were
analyzed based on the recommendations of
Reid & Holdway,1995; Humphrey et al.,
2003; Fugimoto et al., 2004; Fujimoto et al.,
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Int.J.Curr.Microbiol.App.Sci (2020) 9(6): 2170-2177
(2006); Radael et al., (2013); Mattos et al.,
2014. The time at which 50% of the eggs
investigated attained similar stage, the
embryonic developmental stage were
considered. The important water quality
parameters viz. temperature, pH and dissolved
oxygen were measured by thermometer,
digital hand held pH probe on a daily basis.,
ammonia (NH3-N), nitrite (NO2-N), nitrate
(NO3-N), Free carbon dioxide and Total
hardness were also measured daily as per the
standard protocols of APHA, 1998.
Results and Discussion
Water quality
In order to restrict any abrupt water quality
parameter the experiment was carried in a
closed environmental condition. The physiochemical parameters of water in which the
eggs were kept were in the recommended
levels via. Temperature, 29.2 ±0.04°C; pH,
6.60 ± 0.12; 7.9mg/l ±0.25; Nitrite levels and
total ammonia were never greater than 0.01
mg l-1 and 0.3 mg l 1 respectively over the
entire course of the experiment. The mean
value observed for alkalinity and hardness
were 30± 0.17 mg CaCO3 l-1 and 50 ± 0.28
mg CaCO3 l-1 respectively.
Embryonic development
The embryonic developmental stage were
described based on the recommendations of
Fujimoto et al., 2004; Humphrey et al., 2003
and Reid & Holdway, 1995.The stages were
divided into five major period viz. cleavage,
blastula, gastrula, organogenesis and eclosion
stage.
Cleavage period
The period in which the blastomere divide
incessantly doubling their numbers in each
division until the blastodics has 64
blastomeres is termed as cleavage period
(Fujimoto et al., 2004). The 1st cleavage
started 1hr after fertilization where two round
blastomeres were formed by the division of
blastomere by cleavage plane, right angle to
the axis between second polar body and the
micropyle. Eight and thirty two blastomeres
of equal size were formed due to the division
of four and sixteen blastomers was noticed at
3hr and 5hrs after fertilization respectively.
The final cleavage division occurred at 9.5 hr
after fertilization leading to formation of 64
equal blastomeres by mitotic division of 32
blastomers. The final cleavage division
resulted in formation of blastodisc with
overlapping layers of blastomers.
Eggs characteristics
Blastula period
Newly released egg were oval shaped and
yellow in colour with an average diameter of
1.37 ± 0.14 mm. These are adhesive in nature
and found attached to a solid substratum. As
discus eggs have large amount of yolk they
are considered as polilecios.
The organelles are mostly present in the
animal pole and the yolk is concentrated at
the vegetal pole of the egg. The unfertilized
eggs are off white in colour and have a very
touch sensitive chorion compared to a
fertilized egg (Mattos et al., 2014) (Plate 1).
A continued existence between the
blastoderm and the yolk sac limits was
noticed during this stage. Blastula stage
occurred after the seventh cleavage which
resulted in the formation of 128 bastomere
and lasted till the formation of 1024
blastomeres. Four to five layers of
blastomeres with more than 2000 cells are
noticed within the dome shaped blastoderm at
this stage of development. Depending on the
position of each blastomers, the blastomers
gets divided but the plane of cannot be
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practically observed (Yokoya, 1966). In case
of discus eggs this phase progressed from 9.5
hpf till 18.5 hpf during which the eggs
became more or less rounded in shape
Gastrula period
The most distinct characteristics of this stage
is the appearance of epibole. The blastoderm
expands over the surface of the yolk sac and
the embryonic region of the egg can be easily
identified as in this stage the blastoderm gets
thickened. In the latter stage of Gastula, a
well defined germ ring was observed.
A weak but rhythmic movement in the egg
was noticed and the blastoderm covers the
entire yolk sac region, 10 % of yolk vesicle
was covered at 22hpf. About 50% of the yolk
was covered by blastoderm at 28 hpf and 90%
at 32.5 hpf. This stage is characterized with
the differentiation of embryonic axis which
appears as an amber colour line beside the
yolk sac margin. Gastrula stage completes
covering the yolk by the merging of
blastoderm edges which was observed at
33.30 hpf in discus egg.
Eye development
Rudimentary eye vesicles resulted due to the
evagination of cephalic region of the
embryonic axis were formed on each side of
the cephalic region in the embryo at 35.0 hpf.
A well-defined and evident ocular vesicle was
noted at 39.5 hpf.
Somites formation
Somites are rudimentary structures that are
precursor of vertebrate, ribs and axial
musculature of the animal. In S.aequifasciatus
embryos they were initially observed at 33.30
hpf. In the latter period these somites increase
in numbers i.e 10 pairs were observed at 35
hpf and 19 pairs at 41.5 hpf.
Embryonic pigmentation
Early signs of the pigmentation were
observed as small melanophores in the yolk at
39.5 hpf. Consequently, more number of
melanopores was found to be concentrated in
the dorsal portion of the yolk and also in the
ventral region of the embryo.
Organogenesis period
Circulatory system
Organogenesis leads to formation and
differentiation of major organelles. In case of
discus this phase starts from the gastrula
phase during which the embryonic axis was
observed.
In discus early circulatory system consists of
a rudimentary heart which showed early
cardiac movement at 45.5 hpf but it was not
possible to ascertain the blood circulation. At
56.0 hpf the blood of discus embryo gets
pigmented and the blood circulation was
easily observed.
Differentiation of head and tail
The embryonic axis differentiated into
cephalic and caudal region with the closer of
blastomere 33:30 hpf. The separation between
the two extreme were clearly marked by the
prominence of anterior portion of the
embryonic axis. Notable appearance of optic
primodium and seven pairs of somites were
observed in this stage.
Muscle contraction
Very slow muscle contraction was observed
at 53.0 hpf. Gradually the contraction gets
vigorous with the progress of time, noticeable
contraction was observed at 56.5 hpf. There is
an intensification of the contraction till
hatching which caused disruption of chorin
leading to hatching of the egg.
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Vigorous muscle contraction was observed
which resulted in breaking of chorion.
Hatching occurred at 61.10 hpf. The early
hatchling had an underdeveloped digestive
system without a well-defined mouth which
was recognizable at 83.0 hpf.
as Betta splendens (Duarte et al., 2012),
Melanotaenia praecox (Radael et al., 2013)
and Glossolepis incisus (Ferreira, 2007).The
start of organogenesis was marked with the
differentiation of embryonic axis after the
gastrula period, similar observations were
reported by Humphrey et al., (2003) in
Melanotaenia splendid.
A discus egg poses similar external
morphology as shown by the eggs of other
cichlid family viz. Astronotus ocellatus eggs.
Paes et. al. (2012). Discus eggs are adhesive
in nature which can be related to eggs of
Cichlasoma dimerus (Meijide & Guerrero,
2000).The adhesive nature of eggs is
considered as an survival strategy adopted by
many fish species Nakatani et al., (2001).In
the present study, a reduction in blastomere
was observed at the beginning of embryonic
development in the cleavage stage which
coincides with the study of Puvaneswari et
al., (2009) in of Heteropneustes fossilis. The
development o blastula took a longer period
when compared with other fish species such
With the meeting of the two edges of the
blastomere, the closer of the blastomere was
established which is observed at the end of
epibole stage concurrent to the studies of
Puvaneswari et al., (2009) and ReynalteTataje et al., (2004) in Heteropneustes fossilis
and Brycon orbignyanus respectively.The
closer of blastopore is considered as a
significant
stage
in
the
embryonic
development in which decides the success of
fertilization of the oocyte. Woynarovich &
Horváth, 1983. Head and tail was observed
more evident after beginning of segmentation.
In
Channa
striatus,head
and
tail
differentiation reported approximately 11 hpf
(Marimuthu&Haniffa,2007).
Eclosion
Table.1 The range of the water quality parameters observed during experimental period
Water quality parameters
Temperature(0C)
Range
28-31.5
As per
Experimental
Design
pH
Dissolved oxygen (mgl-1)
5.2-6.8
Free carbon dioxide (mgl-1)
-1
0-4
48-62
Total hardness (mgl )
Ammonia-nitrogen (NH3-N)
0.01-0.04
Nitrite-nitrogen (NO2-N)
0-0.02
Nitrate-nitrogen (NO3-N)
0.48-2.13
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Plate.1 Embryonic Developmental Stage in Discus
(A) Recently fertilized egg with only one blastomere (B) 4 cell embryonic stage
(C) Blastula Stage (D) Gastrula (E) Organogenesis (F) Hatchlings
Discus larvae are typical example of altricial
larvae where hatching of discus eggs takes
place even before the complete formation of
the embryo identical feature was recorded in
neotropial larvae Nakatani et al., (2001).The
larvae were found adhered to the substrate
after the eclosion of the eggs by adhesive
substance secreted by glands located in the
base of eye and head, which is considered as
a strategy to minimize scattering of larvae
into the water column .The above strategy
followed are associated to parental care
observed in discus, similar observation s are
noticed in other fish species like Cichlasoma
dimerus (Meiji de & Guerrero, 2000) and
Astronotus ocellatus by Paes et. al., (2012).
The ocular structure of discus developed in a
similar fashion as reported in other species
and it was attained at 46.5 hpf. In case of M.
praecox and tilapia (Oreochromis niloticus),
the optic primodium was formed at 21.89 hpf
and 44 hpf as reported by Radael et al.,
(2013) and Okada (2007) respectively. Early
hatching had un pigmented and under
developed eyes, eventually after the yolk
absorption stage the eyes were pigmented and
was fully developed . From this experiment it
can be noted that discus eggs hatches at 61.10
hpf and have similar characterstics as shown
by other cichlids species.
References
Anjos, H.D.B. and Anjos,C.R.,
2006.
Reproductive biology and embryonic
and larval development of the cardinal
tetra, Paracheirodon axelrodi Schultz,
1956 (Characiformes: Characidae), in
laboratory. Bol. Inst. Pesca, 32, 151166.
2175
Int.J.Curr.Microbiol.App.Sci (2020) 9(6): 2170-2177
Chellappa, S., Câmara, M. R. and Verani.J.
R., 2005. Ovarian development in the
amazonian red discus, Symphysodon
discus,
Heckel
(Osteichthyes:
Cichlidae). Brazilian Journal of
Biology, 65, 609-616
Chong, K., Ying, T.S., Foo, J., Jin, L.T and
Chong, A., 2005. Characterization of
proteins in epidermal mucus of discus
fish (Symphysodon spp.) during
parental phase. Aquaculture 249, 469476.
Duarte, S.C., Vasconcellos, B.F., Vidal Jr.,
M.V., Ferreira, A.V., Mattos., D.C. and
Branco, A.T., 2012. Ontogeny and
embryonic
description
of
Betta
splendens, Perciformes (Regan, 1910).
Revista Brasileira de Saúde e Produção.
Animal 13, 880–93.
Ferreira, A.V., 2007. Ontogenia Inicial E
Consumo De Vitelo Em Embriões De
Melanotaenia
Maçã
(Glossolepis
incisus, Weber, 1907). Dissertação.
Universidade Estadual do Norte
Fluminense Darcy Ribeiro, Campos dos
Goytacazes., 64 pp
Fujimoto, T, Kataoka, T, Sakako, S., Saito, T.
Yamaha,
E
and
Arai,
K.
2006.Developmental stages and germ
cell lineage of de loach (Misgurnusan
guillicaudatus). Zoological Society of
Japan, v.23. p.977-989.
Fujimoto, T, Kataoka., T, Otani, S., Saito, T.,
Aita, T., Yamaha,E. and Arai, K., 2004.
Embryonic stages from cleavage to
gastrula in the loach Misgurnusan
guillicaudatus. Zoolog.Sci.Jpn 21, pp.
747–755.
Godinho, H.P., Santos, J.E. and Sato, Y.,
2003. Ontogênese larval de cinco
espécies de peixes do São Francisco,
pp.133–148. In H.P. Godinho & A.L.
Godinho (eds.). Águas, Peixes e
Pescadores do São Francisco das
Minas Gerais. Belo Horizonte: PUC
Minas, 468 pp.
Humphrey, C., Klumpp, D. W. and Pearson,
R., 2003.Early development and growth
of the east rainbowfish, Melanotaenia
splendida
splendid
(Peters).
I.
Morphogenesis and ontogeny. Mar.
Freshwater Res.54, 17–25.
Joblin, M.,2002 . Environmental factors and
rates of development and growth. P.J.B.
Hart, J.D. Reynolds (Eds.), Handbook
of Fish Biology and Fisheries, vol. 1,
Fish Biology Blackwell Science Ltd.
Blackwell Publishing Company.
Liew, H. J., Ambak, M. A., and Abol-Munafi,
A. B., 2006. Embryonic development of
clownfish Amphiprion ocellaris under
laboratory conditions. Journal of
Sustainable Science and Management,
1(1), 64–73.
Marimuthu, K. and Haniffa, M.A., 2007.
Embryonic and larval development of
the striped snakehead Channa striatus.
Taiwania.52, 84–92.
Mattos,D.C, Leonardo, D. C, Paulo José
Fosse, M. C., Radael, J. C., Fosse, F.,
JoãoVitor, Dalcio, R.A and Manuel, V.
V., 2014. Description of the ontogenic
and larval period of discus fish
(Symphysodona equifasciatus).Zygote.
7, 7-11.
Meijide, F.J and Guerrero, G.A., 2000.
Embryonic and larval development of a
substrate-brooding cichlid Cichlasoma
dimerus
(Heckel,
1940)
under
laboratory conditions. J. Zool.252, 481–
93.
Moyle, P.B and Cech, J.J.J.R., 2004. Fishes:
an introduction to ichthyology, 5th edn.
Pearson Prentice-Hall Inc. Upper
Saddle River, NJ, 82-96.
Okada, N and
Fujimura, K., 2007.
Development of the embryo, larva and
early juvenile of Nile tilapia Oreochromis
niloticus (Pisces: Cichlidae). Dev. Growth
Diff. 49, 301–24.
Paes, M.C.F., Makino, C.L., Vasquez, A.L.,
Fernandes, K.B.J. and Nakaghi, O.S.L.,
2176
Int.J.Curr.Microbiol.App.Sci (2020) 9(6): 2170-2177
2012. Early development of Astronotus
ocellatus under stereomicroscopy and
scanning electron microscopy. Zygote,
20, 269–76.
Puvaneswari,
S.,
Marimuthu,
K.,
Karuppasamy, R. & Haniffa, A.M.,
2009. Early embryonic and larval
development
of
Indian
catfish,
Heteropneustes fossilis. EurAsianJ.
BioSci. 3, 84–96.
Radael,M.C, Leonardo, D. C, Dalcio Ricardo,
A.D.M, Jonas, Henrique Motta,
JoãoVitorManhães and Manuel, V. V.,
2013.
Morphophysiological
characterization of the embryonic
development of Melanotaenia praecox
(Weber & de Beaufort, 1922).Zygote,
533–539.
Reid, H.P and Holdway, D.A., 1995. Early
development of the Australian crimson
spotted rainbowfish, Melanotaenia
fluviatilis (Pisces: Melanotaeniidae).
Marine and Freshwater Research, 46 :
475-480.
Reynalte-Tataje, D., Zaniboni-Filho, E. and
Esquivel, J.R., 2004. Embryonic and
larvae development of piracanjuba,
Bryconorbignyanus Valenciennes, 1849
(Pisces, Characidae). Acta Scientiarum.
Biol. Sci.26, 67–71.
Santos, G., Ferreira, E. and Zuanon, J., 2006.
Peixes comerciais de Manaus. Manaus,
Ibama. AM, Provárzea. 144 pp.
Senhorine, J.A., 1993. Procedimento para
criação
de
larvas
de
peixes.
IBAMACEPTA. Pirassununga – São
Paulo. Apostila 21 pp.
Vallin, L. and Nissling, A., 1998. Cell
morphology as an indicator of viability
of cod eggs — results from an experimental study. Fisheries Research, 38,
247–255.
Wattley, J., 1991. Discus for the Perfectionist.
T.F.H Publications, 125 pp.
Woynarovich, E. and Horváth, L., 1983. A
Propagação Artificial de Peixes de
águas tropicais: Manual de Extensão.
Brasília:FAO/CODEVASF/CNP, 13 pp.
Yokoya, S., 1966. Cell dissociation and
reaggregation in early stage embryo of a
teleost, Oryzias latipes. Scient. Rep.
Tohoku Univ. (Ser. IV, Biol.), 32, 229236
How to cite this article:
Sambid Swain, Paramita Banerjee Sawant, J. K. Sundaray, E. M. Chhandaprajnadarsini and
Milind B. Katare. 2020. Embryonic Development of Discus, Symphysodon aequifasciatus
Pellegrin, 1904 in Indian Condition. Int.J.Curr.Microbiol.App.Sci. 9(06): 2170-2177.
doi: https://doi.org/10.20546/ijcmas.2020.906.265
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