A tamerican museum
Novitates
PUBLISHED
CENTRAL
BY
THE
PARK
AMERICAN
WEST
AT
MUSEUM
79TH
STREET,
Number 3576, 16 pp., 7 figures, 2 tables
OF
NATURAL
NEW
YORK,
HISTORY
NY
10024
June 28, 2007
Congochromis, a New Cichlid Genus
(Teleostei: Cichlidae) from Central Africa, with
the Description of a New Species from the Upper
Congo River, Democratic Republic of Congo
MELANIE L. J. STIASSNY1 AND ULRICH K. SCHLIEWEN2
ABSTRACT
Congochromis, a new cichlid genus, is described on the basis of a suite of anatomical features of the
cephalic laterosensory system, infraorbital series, oral dentition, and squamation. As recognized
herein, Congochromis comprises three species formerly included in the genus Nanochromis (N.
squamiceps, N. dimidiatus, and N. sabinae) and a new species from the vicinity of Kisangani
(Stanleyville) on the upper Congo River. Diagnostic features for Congochromis and Nanochromis
s.str. are provided. Congochromis pugnatus, n.sp. is diagnosed by the possession of a distinctive
pattern of hypural fusion, a strongly inclined lower jaw, and an expanded cheek musculature.
INTRODUCTION
The increased rate of species discovery and
description in the Congolese cichlid genus
Nanochromis Pellegrin (see Lamboj, 2005;
Schliewen and Stiassny, 2006; Lamboj and
Schelly, 2006) is typical of a growing docu¬
mentation of the high levels of species di¬
versity among freshwater fishes in the Congo
River basin (Schelly and Stiassny, 2004;
Stiassny and Schaefer, 2005; Schliewen and
Schafer, 2006; Stiassny et al., 2006; Tshibwabwa et al., 2006). As species discovery rates
increase, a concomitant understanding of
phylogenetic relationships is necessary to pro¬
vide a framework for investigation of the
mechanisms and processes underlying contem¬
porary aquatic diversity. To date, eleven
Nanochromis species have been described,
and a number of additional taxa are awaiting
1 Division of Vertebrate Zoology, Department of Ichthyology, American Museum of Natural History, (mljs@amnh.
org).
2 Department of Ichthyology, Bavarian State Collection of Zoology, Mimchhausenstr. 21, D-81247 Munchen, Germany
(schliewen@zsm .mwn).
Copyright © American Museum of Natural History 2007
ISSN 0003-0082
2
AMERICAN MUSEUM NOVITATES
formal description (Schliewen and Stiassny,
2006, personal obs.; Lamboj, in litt.). In
a recent study, Schliewen and Stiassny (2006)
discussed the presence of two informally
named groups within Nanochromis: a nudiceps
group and a squamiceps group. Both groups
are diagnosable on the basis of derived
anatomical features, and herein we restrict
the genus Nanochromis s.str. to include the
type species N. nudiceps (Boulenger, 1899) and
seven congeners: N. consortus Roberts and
Stewart, 1976, N. minor Roberts and Stewart,
1976, N. parilus Roberts and Stewart, 1976, N.
splendens Roberts and Stewart, 1976, N.
teugelsi Lamboj and Schelly, 2006, N. transvestitus Stewart and Roberts, 1984, and N.
wickleri Schliewen and Stiassny, 2006. The
species of the squamiceps group are herein
formally recognized as members of the new
genus, Congochromis, with C. squamiceps
(Boulenger, 1902) as the type species, along
with C. dimidiatus (Pellegrin, 1900), C. sabinae
(Lamboj, 2005), and a new species from the
vicinity of Kisangani on the upper Congo
River described herein.
MATERIALS AND METHODS
Counts and morphometric measurements
follow Barel et al. (1977), with the following
exceptions: predorsal length is measured as the
distance between the dorsal fin origin and
snout tip. Preanal length is measured as the
distance between the anal fin origin and snout
tip. Depth of the head is measured from the
top of the head at midorbit to the ventral edge
of the interopercle. Measurements were re¬
corded to the nearest 0.1 mm using digital or
dial calipers. Vertebral counts exclude the
terminal, hypural-bearing vertebra, and verte¬
bral and fin spine/ray counts and measure¬
ments were obtained from radiographs or
cleared-and-stained
skeletal preparations.
The terminal dorsal and anal soft fin rays
are counted as single elements, even if
branched and split to the fin base when the
element is associated with a single supporting
pterygiophore. Gill raker counts correspond
to the lower limb of the first arch and include
the raker in the angle of the arch marking the
transition from ceratobranchial to epibranchial.
NO. 3576
Comparative material comprised formalinfixed specimens stored in 70-75% ethanol,
nonformalin-fixed specimens stored in 7095% ethanol, and specimens cleared and
stained for bone and cartilage using a modified
protocol based on Taylor and Van Dyke
(1985). When sufficient material was available,
multiple cleared-and-stained specimens were
prepared and examined for each species.
Institutional abbreviations follow Leviton et
al. (1985). The following comparative materi¬
als have been included in the study (values
after catalog number indicate number of
specimens examined, and do not necessarily
correspond to the total number of specimens
in the lot; C&S indicates cleared-and-stained
preparation; SL, standard length; HL, head
length):
Benitochromis finleyi: AMNH 238254, 1 ex.
C&S, Cameroon.
Benitochromis riomuniensis: CU 90064, 15 ex.,
Lobe River, Cameroon.
Chromidotilapia mamonekenei: AMNH 232367,
14 ex., 1 C&S, 27 km from Tchibanga,
Gabon.
Chromidotilapia mrac: AMNH 229522, 5 ex.,
1 C&S, Mikouma River, Moyen-Ogooue,
Gabon.
Congochromis dimidiatus: MNHN 1892-0120,
syntype, 1 ex., Bangui; MNHN 1892-0121,
syntypes, 3 ex., Bangui; MNHN 1920-01946, 3 ex., Bangui; AMNH 8150, 3 ex., 1 C&S,
Bangui River at Bangui.
Congochromis sabinae: AMNH 235651, paratype, 1 ex., Loubi River, Likouala River
drainage; AMNH 235652, paratype, 1 ex.,
Loubi River, Likouala River drainage;
AMNH 227666, 1 ex., Lossi Creek,
Sangha River drainage; CU 88552, 1 ex.,
Mambili River, Likouala River drainage.
Congochromis squamiceps: BMNH 1902.4.14:
11, syntype, 1 ex., Lindi River, Upper
Congo; IRSNB 13, syntype, 1 ex., Lindi
River, Upper Congo; AMNH 225399, 1 ex.,
Kisangani (Stanleyville), Upper Congo.
Divandu albimarginatus: AMNH 232347, 4
ex., Onoy River at Bandi, Gabon.
Nanochromis consortus: AMNH 233375, 1 ex.,
Nziya, Congo River; AMNH 236667, 1 ex.,
Nziya, Congo River; MCZ 50552, paratypes, 5 ex., 1 C&S, mainstream Congo
River, near Inga.
2007
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
Nanochromis minor: AMNH 237660, 1 ex.
C&S., 2 km upstream of Kinganga, Congo
River; MCZ 50342, paratypes, 2 ex., main¬
stream Congo River, downstream from
Kinganga.
Nanochromis nudiceps: MR AC 1045, lectotype, Kutu.
Nanochromis parilus: MCZ 50202, paratypes,
8 ex., 1 C&S, mainstream Congo River,
near Wombe.
Nanochromis splendens: MCZ 50477, para¬
types, 6 ex., 1 C&S, mainstream Congo
River, near Inga.
Nanochromis transvestitus: ZSM 29705, 9 ex.,
2 C&S, Lake Mai Ndombe, near Inongo.
Nanochromis teugelsi: AMNH 233374, paratype, 1 ex., Bandundu province, Bokoni
village, Kasai River, estuary across river.
Nanochromis wickleri: AMNH 236666, paratype, 1 ex. C&S, Lake Mai Ndombe at
Inongo; AMNH 236665, paratype, 1 ex.,
Lake Mai Ndombe at Inongo.
Nanochromis sp.: AMNH 233569, 1 ex.,
Bobongo Creek into Sangha, Central
African Republic.
Parananochromis gabonicus: CU 80730, 1 ex.
C&S, Minka Creek, 7 km south of Oyem,
Gabon; AMNH 211142, 4 ex., Nye River,
Woleu-Ntem, Gabon.
Parananochromis longirostris: AMNH 230708,
7 ex., 1 C&S, Ivindo River, Gabon.
Pelvicachromis humilis: AMNH 22238, 1 ex.
C&S, River Moa, Sierra Leone.
Pelvicachromis taeniatus: AMNH 216147, 1
ex. C&S, no data; CU 90064, 10 ex., Lobe
River, Cameroon.
Teleogramma brichardi: MCZ 48009, 1 ex.
C&S, Congo River, rapids at Kinsuka.
Thysochromis ansorgii: AMNH 235828, 2 ex.,
Benin; AMNH 216147, 1 ex. C&S, no data.
Throughout this paper the phylogenetic
species concept is adopted as a basis for species
diagnosis. Congolese place names follow con¬
temporary usage, and equivalent colonial-era
place names previously utilized in the literature
are given within brackets following their initial
appearance in the body of the text.
PRINCIPAL COMPONENTS ANALYSIS
To investigate species boundaries between
the morphologically similar members of
3
Congochromis, we have performed an explor¬
atory multivariate analysis of 16 log-trans¬
formed morphometric variables using a sheared
principal components analysis (PCA) (Hum¬
phries et al., 1981; Bookstein et al., 1985).
Principal components were factored from the
covariance matrix of log-transformed variables.
The PCA was conducted in Sheared PCA,
a freeware program written for the Macintosh
operating system by Norman Macleod and
available for download at http://www.nhm.ac.
uk/hosted_sites/paleonet/ftp/ftp.html.
GENERIC DIAGNOSES
In the following generic diagnoses and
accompanying illustrations an asterisk pre¬
cedes character numbers, and character states
are indicated by superscript numerals. Based
on outgroup comparison among other chromidotilapiines and related cichlid species the
use of superscript “1” indicates the hypothe¬
sized derived state and superscript “0” the
plesiomorphic state for each figured character.
Nanochromis Pellegrin, 1904
Type species: Nanochromis nudiceps (Boulenger, 1899)
[Type locality: Kutu, Lake Leopold II, Zaire (Lake Mai
Ndombe, Democratic Republic of Congo)].
Included species: N. consortus Roberts and Stewart, 1976,
N. minor Roberts and Stewart, 1976, N. parilus Roberts
and Stewart, 1976, N. splendens Roberts and Stewart,
1976, N. teugelsi Lamboj and Schelly, 2006, N.
transvestitus Stewart and Roberts, 1984, and N. wickleri
Schliewen and Stiassny, 2006.
Nanochromis is diagnosed by the following
combination of apomorphic features: at least
the posterior half of the upper lateral line
contiguous with the dorsal-fin base; presence
of an asquamate nape, cheek, and belly;
absence of a supraneural bone; possession of
extremely fine, closely spaced unicuspid teeth
in upper and lower jaws (fig. 1, *1! vs. *1°);
presence of a horizontally oriented, elongate
second infraorbital (fig. 1, *2l vs. *2°).
Nanochromis shares with Congochromis, its
putative sistergroup, the apomorphic features
of an elevated lateral line that is at least
partially contiguous with the dorsal fin (less
extensively so in Congochromis), a characteris¬
tic reduction of the infraorbital series consist¬
ing of a single, elongate element behind the
first infraorbital (preorbital) (figs. 1, 5A), and
4
AMERICAN MUSEUM NOVITATES
NO. 3576
Fig. 1. Isolated infraorbital series, oral jaws, and suspensoria of (A) Congochromis dimidiatus, AMNH
8150, (B) Nanochromis parilus, MCZ 50202, and (C) Nanochromis minor, AMNH 237660.
an exoccipital contribution to the ventral
articular surface of the pharyngeal apophysis.
Congochromis, new genus
Type species: Congochromis squamiceps (Boulenger, 1902)
[Type locality: Lindi, Lindi River, Upper Congo, Zaire
(Democratic Republic of Congo)].
Included species: C. dimidiatus (Pellegrin,
sabinae (Lamboj, 2005), C. pugnatus, n.sp.
1900),
C.
Congochromis is diagnosed by the following
combination of apomorphic features: four
pores in the dentary laterosensory canal
(fig. 1, *3* vs. five pores, *3°), absence of
a laterosensory canal in the angulo-articular
(fig. 1, *4! vs. *4°), and six pores in the
2007
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
5
Fig. 2. Caudal fin skeleton of (A) Parananochromis gabonicus (CU 80730), (B) Nanochromis parilus
(MCZ 50202), (C) Congochromis pugnatus (AMNH 237670), (D) C. squamiceps (recorded from a radiograph
of IRSNB 13), (E) C. sabinae (recorded from radiographs of AMNH 235651-2), and (F) C. dimidiatus
(AMNH 8150).
preopercle laterosensory canal (fig. 1, *5* vs.
seven pores, *5°).
The following combination of features
distinguishes Congochromis from Nanochr¬
omis: only the last three to five pored scales
of the upper lateral line are contiguous with
the dorsal-fin base (vs. at least the posterior
half of the upper lateral line contiguous); fully
scaled nape, and partially scaled chest and
cheek (vs. an asquamate nape, chest, and
cheek); jaw teeth relatively robust unicuspids,
not closely spaced (vs. extremely fine, closely
spaced unicuspids); and the presence of
a small, supraneural bone (vs. absence).
AMERICAN MUSEUM NOVITATES
6
Fig. 3. Head squamation of Congochromis
pugnatus (paratype, AMNH 237670); gray area on
cheek indicates region of expanded adductor mandibulae musculature.
Congochromis pugnatus, new species
figures 3-5
Holotype:
AMNH 6079, 48.2 mm SL,
adult male, Democratic Republic of Congo,
Kisangani (Stanleyville), H. Lang and J.P.
Chapin, May 1915.
Paratypes:
Eight paratypes with same
data as holotype: AMNH 237670, 2 ex., 1
C&S, 37.0-51.5 mm SL; FMNH 57121, 3 ex.,
37.8-49.1 mm SL; MRAC 2006-45-P-l,
50.4 mm SL; ZSM 34981, 2 ex., 37.049.2 mm SL.
Diagnosis:
A Congochromis diagnosed by
the possession of a compound urostyle + fused
hypural plate (fig. 2C). Further differs from
all congeners in possessing a strongly inclined
lower jaw and expanded cheek musculature
(fig- 3).
Description:
Based on the holotype and
eight paratypes. See table 1 for a summary of
morphometric and meristic data for the new
taxon and for comparative data on type
specimens of all congeners. Morphological
characteristics and general pigmentation pat¬
tern can be observed in figure 4, and of
congeners in figure 6. A robust, relatively
deep-bodied species (depth 29.3-35.5%, mean
31.7% SL). Greatest body depth at (males), or
slightly behind (females), level of pelvic-fin
NO. 3576
insertion. Head short (length 31.2-33.2%,
mean 32.1% SL) and deep (depth 21.225.1%, mean 23.1% HL). Cheek deep (depth
24.4-28.8%, mean 26.2% HL). Snout short
and broad, jaws isognathous, with lower jaw
strongly inclined and ventral section of ad¬
ductor mandibulae muscle large and bulbous
in anteroventral region of cheek (fig. 3). Lips
well developed and fleshy, lower lip fold
discontinuous at symphysis. Dorsal head pro¬
file straight to midorbit, bulbous to dorsal fin
origin; markedly so in large males. Dorsal
body profile curving gently downward along
length of dorsal fin base to short, deep caudal
peduncle. Ventral body profile more or less
straight (males) or strongly convex (females).
Flanks covered with large, regularly imbri¬
cating, cycloid scales. A few deeply embedded,
cycloid scales scattered over opercle and
subopercle. Cheek with small round, cycloid
scales restricted to one or two rows at
dorsoposterior margin. Occipital region with
numerous small, imbricating cycloid scales to
level of midorbit. Small cycloid scales over
pectoral-fin base, chest naked. Belly scales
slightly smaller with a gradual transition in
size; scales on ventral portion of belly and
anal-genital region of same size as lateral belly
scales. Upper lateral line originates behind
occipital margin of opercle, ascends gradually
to dorsal-fin base reaching highest point at
level of 10th to 12th dorsal fin spine, continues
with half an intervening scale or no interven¬
ing scale between lateral line and dorsal-fin
base. Pored scales interspersed with more
numerous nonpored scales along length of
upper lateral line. Lower lateral line short,
usually consisting of only two or three pored
scales interspersed among nonpored scales.
Upper lateral line separated from lower lateral
line by two scales (excluding pored rows).
Caudal-fin base with a single large pored scale
medially (not included in longitudinal scale
count) and numerous small scales over basal
eighth of fin.
Dorsal fin with XVI-XVIII (mode XVII)
spines and 6-9 (mode 8) rays. Anal fin with III
spines and 5-6 (mode 6) soft rays. Dorsal-fin
spines gradually increase in length to 14th or
15th spine, remaining spines of equal length.
Soft dorsal and anal fins in males with
tapering filamentous extensions reaching to
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
TABLE 1
Morphometric and Meristic Data for the Holotype and Eight Paratypes of Congochromis pugnatus, n.sp., Two Syntypes of C. squamiceps. Two Largest
Syntypes of C. dimidiatus, and Two Paratypes of C. sabinae
2007
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AMERICAN MUSEUM NOVITATES
NO. 3576
Fig. 4. Congochromispugnatus: (A) AMNH 6079, holotype, male, 48.2 mm SL, Democratic Republic of
Congo, Kisangani (Stanleyville), May 1915, H. Lang and J.P. Chapin; (B) AMNH 237670, paratype, female,
37.0 mm SL, same data as holotype.
basal third of caudal fin. In females soft dorsal
and anal fins are pointed but not produced
and do not reach base of caudal fin. Caudal
fin rounded with 14 branched rays; appears
lance-shaped, subacuminate when adducted.
First pelvic fin ray longest in both sexes,
reaching anal fin base in males, shorter in
females. Pectoral fin rounded, reaching verti¬
cal approximately at midpoint of spinous
dorsal fin.
Eight to 10 small gill rakers along outer row
of lower limb of first gill arch (including larger
more elongate raker in angle of arch) and
three to five bulbous epibranchial rakers
(fig. 5C). In common with most other chromidotilapiine cichlids, a prominent visorlike,
hanging pharyngeal pad is developed on
epibranchial 2, and no microbranchiospines
are present on outer face of second, third, or
fourth gill arches.
Outer row dentition on both premaxilla and
dentary composed of relatively robust, re¬
curved, unicuspid teeth (fig. 5B). Teeth are
evenly spaced along each jaw, three or four
symphysial teeth on dentary somewhat en¬
larged
and
procumbently
implanted.
Anteriorly in both jaws three to four short
inner rows of recurved teeth taper to a single
row posteriorly.
Lower pharyngeal jaw (fig. 5D) relatively
gracile, with narrow horns and a short blunt
keel. Dentigerous surface sparsely covered
with bicuspid teeth. Posterior row teeth
elongate, erect, closely spaced bicuspids with
strongly hooked major cusp and smaller
minor cusp. Anteriorly lower pharyngeal jaw
teeth weakly erect, somewhat shouldered,
robust, unicuspids.
Vertebrae column with a total of 26-27
(mode 26) vertebrae.
2007
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
9
Fig. 5. Congochromispugnatus, AMNH 237670, paratype, male, 51.5 mm SL: (A) infraorbital series, (B)
suspensorium and jaws, (C) 1st gill arch, and (D) lower pharyngeal jaw.
Miscellaneous Osteology And Anat¬
In common with other Congochromis,
the first infraorbital of C. pugnatus has four
sensory canal pores and is followed by a single,
elongate, dorsoposteriorly oriented infraorbi¬
tal element (fig. 5A). Four pores perforate the
laterosensory canal in the dentary, the anguloarticular lacks a canal, and six pores
perforate the preopercular canal (fig. 5B).
The pharyngeal apophysis has an extensive
exoccipital contribution to the ventral articu¬
lar surface of the apophysis.
Primitively in the caudal skeleton of chromidotilapiines the hypural plate is comprised
omy:
of five separate hypural elements, each of
which articulates with an autogenous terminal
urostyle (e.g., fig. 2A, B). In Congochromis
various patterns of hypural fusions are evident
(e.g., fig. 2C-F), but uniquely in C. pugnatus
hypurals 1+2 and 3+4 are fused into a single
element, and the resultant compound hypural
plate is fused with the urostyle (fig. 2C); this is
the case even in the smallest specimens
examined. By contrast, C. sabinae (fig. 2E),
C. squamiceps (fig. 2D), and C. dimidiatus
(fig. 2F) have hypurals 3+4 (or 3 and 4 in the
case of C. dimidiatus) fused with the urostyle,
but hypurals 1+2 (C. sabinae) or hypurals 1
10
AMERICAN MUSEUM NOVITATES
NO. 3576
Fig. 6. (A) Congochromis squamiceps, IRSNB 13, syntype, male, 47.5 mm SL, Lindi River, Upper
Congo, (B) C. dimidiatus, MNHN 1892-0120, syntype, male, 44.5 mm SL, Bangui, (C) C. sabinae, AMNH
235651, paratype, male, 48.0 mm SL, Loubi River, southwest of Makoua.
and 2 (C. squamiceps and C. dimidiatus)
remain autogenous, even in the largest speci¬
mens available for study. In C. pugnatus the
adductor mandibulae muscle is well devel¬
oped, and in large individuals the anterioven¬
tral portion of the muscle complex is enlarged
and voluminous, lending a characteristic bulge
to the cheek (fig. 3).
Coloration in Preservative (fig. 4):
Ground
color is more or less uniformly pale brown.
Specimens have been in preservative for more
than 90 years and pigmentation is faded;
nonetheless, each flank scale has a narrow
pigmented bar on its exposed posterior edge.
Scale centers retain traces of a silvery irides¬
cence, and this silvery iridescence is most
2007
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
strongly marked midlaterally and over the
bloated abdomen of female specimens. All
specimens lack a clearly defined dark longitu¬
dinal band or series of midlateral blotches
extending from the eye to the caudal peduncle
(males) or end of the caudal fin (females),
a pigmentation that is claimed to be character¬
istic of other Congochromis (Lamboj 2004);
however, the absence of this feature may be an
artifact of long-term preservation. Both males
and females retain a heavily pigmented, scale¬
less opercular blotch. In males the soft dorsal,
anal, and caudal fins are heavily maculate with
alternating rows of light and dark maculae
creating a striped patterning. In females these
fins are hyaline and lack rows of maculae, and
a single large black blotch is present in the soft
dorsal fin (fig. 4B).
Coloration in Life: No data.
Geographical
Distribution: Currently
known only from the Upper Congo from
a single collection from the vicinity of
Kisangani (Stanleyville) in the Democratic
Republic of Congo.
Habitat: The species is currently known
only from historically collected specimens, and
no record of habitat preference is provided by
Nichols and Griscom, who reported only that
the specimens were collected in 1915 during
the AMNH Lang-Chapin Congo Expedition,
in the vicinity Kisangani. The town of
Kisangani lies between the Lindi River and
the Congo mainstream, and as a result it is
possible that Lang-Chapin specimens from
“Kisangani” may refer to collections made in
different rivers. Congochromis pugnatus and C.
squamiceps may occur syntopically in the
vicinity of Kisangani, as indicated by an
individual of the latter species collected by
Lang and Chapin (AMNH 225399) from the
Kisangani locality, but this is unconfirmed at
present.
Etymology: From the Latin pugno, mean¬
ing to contend or fight, in reference to the
heavy-jawed, pugnacious aspect of the species.
DISCUSSION
As is evident from table 1 and figures 4 and
6, species of Congochromis are superficially
very similar, and as a result problems persist in
the identification of materials currently
11
TABLE 2
Loadings of Morphometric Variables in Sheared
Principal Components Analysis for Type Specimens
of Congochromis spp. (fig. 7)
Variable
Standard length
Body depth
Head length
Head depth
Snout length
Preorbital length
Lower jaw length
Oribit diameter (horizontal)
Postorbital length
Cheek depth
Caudal peduncle length
Caudal peduncle depth
Dorsal base
Anal base
Predorsal length
Preanal length
Sheared PC2 Sheared PC3
0.105
0.097
0.075
0.195
-0.257
-0.578
0.278
-0.067
0.216
0.099
0.465
0.170
0.128
0.312
0.109
0.089
0.066
0.001
0.024
-0.107
0.118
0.071
-0.104
0.264
-0.193
-0.710
0.505
0.196
0.067
-0.121
0.101
0.045
housed in museum collections (personal
obs.). Most of these specimens have been
collected more than 30 years ago, and precise
information on locality, coloration, or behav¬
ior are often unavailable to aid in species
assignment. In an effort to investigate species
boundaries between the morphologically sim¬
ilar members of Congochromis, we performed
an exploratory multivariate analysis of 16 logtransformed morphometric variables using
a sheared PC A (Humphries et al., 1981;
Bookstein et al., 1985). Because of the un¬
certainty of species identifications in museum
collections, we have limited this analysis to
include those members of the type series for
each putative species for which we were able to
obtain a full set of morphometric data. The
resultant sample is too small to be of statistical
significance; nonetheless, it is noteworthy that
complete discrimination of a C. pugnatus + C.
squamiceps cluster from C. sabinae and C.
dimidiatus occurred along sheared PC2 (fig. 7
and table 2), while PC3 separates C. sabinae
and C. dimidiatus. Sheared PC2 loaded heavily
for preorbital length, caudal peduncle length,
and length of anal base, and the variables that
loaded most heavily for PC3 were cheek depth
and caudal peduncle length (table 2). Based on
these admittedly limited data, it appears that
C. pugnatus and C. squamiceps, both from the
AMERICAN MUSEUM NOVITATES
NO. 3576
Sheared PCA 2
12
Fig. 7. Scatterplot of sheared second and third PC scores of 16 log-transformed morphometric variables
the type series of Congochromis pugnatus (stars), syntype of C. squamiceps (square), paratypes of C. sabinae
(hexagons), and syntypes of C. dimidiatus (circles) (see table 2 for axis loadings).
2007
STIASSNY AND SCHLIEWEN: NEW CICHLID FROM CONGO
region around Kisangani in the upper Congo,
are currently morphometrically indistinguish¬
able. However, an ongoing radiograph-based
analysis of body shape variation within and
among chromidotilapiine species incorporat¬
ing larger sample sizes suggests a greater
resolving power (Schwarzer, in prep.), but
with the limited material currently available
we are unable to undertake such an analysis.
Nonetheless, anatomically, C. pugnatus and C.
squamiceps are readily separable on the basis
of consistent hypural fusion pattern differ¬
ences.
With the single exception of C. sabinae, with
a range extending into the Liboumba River
(Ogowe drainage) of Gabon, Congochromis
and Nanochromis are restriced to the central
Congo basin. A preliminary survey of exten¬
sive historical material housed in MRAC and
AMNH and from recent collections in
AMNH and ZMS suggests that Nanochromis
s.str. is restricted to the lower Congo main¬
stream and Pool Malebo and to the shallow
lakes Mai Ndombe and Tumba in the Cuvette
Centrale (the “saucer-shaped” part of the
central Congo basin), while species of
Congochromis occur both in small rainforest
streams (C. sabinae), as well as in larger rivers
and lakes (C. dimidiatus, C. pugnatus, C.
squamiceps). Nanochromis appears to be en¬
tirely absent in the Eastern Congo while, to
date, no Congochromis is known from the
lower Congo Rapids, Pool Malebo, or the
Kasai drainage. In combination, this pattern
suggests an allopatric origin of Congochromis
and Nanochromis, as well as intrinsic ecolog¬
ical differences between members of the two
closely related genera, and it highlights the
importance of a fine-scaled analysis of distri¬
butional patterns within the Congo basin and
the Cuvette centrale.
Although a preliminary analysis of both
mitochondrial and nuclear DNA sequence
data in chromidotilapiine cichlids supports
the generic distinction of Nanochromis and
Congochromis (Schliewen and Lamboj, unpubl.), the enigmatic eastern Congolese
Chromidotilapia schoutedeni (Poll and Thys
van den Audenaerde, 1967) as well as the
eburneo-ghanaen endemic Limbochromis robertsi (Thys van den Audenaerde and Loiselle,
1971) form a well-supported clade together
13
with Nanochromis and Congochromis. This
somewhat unanticipated result suggests that
a further analysis, including morphological
data from C. schoutedeni and L. robertsi, is
desirable to resolve the phylogenetic intrar¬
elationships of this group. Such an in-depth
combined analysis is currently in progress.
ACKNOWLEDGMENTS
Our thanks to J. Snoeks, E. Vreven, and M.
Parrent (MRAC), G. Lenglet (IRSNB), G.
Duhamel and P. Pruvost (MNHN), K. Hartel
(MCZ), Mark Westneat (FMNH), and J. Friel
(CU) for loan of material in their care. Thanks
also to A. Lamboj for kindly providing data on
BMNH specimen 1902.4.14:11 and on an
undescribed species of Congochromis. Research
support was provided by the National Science
Foundation (grant number DEB 0542540).
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