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

2007·1.8 MB·English

by  Melanie L. J. Stiassny

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3576, 16 pp., 7 figures, 2 tables 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,anewcichlidgenus,isdescribedonthebasisofasuiteofanatomicalfeaturesofthe
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
patternofhypuralfusion,astronglyinclinedlowerjaw,andanexpandedcheekmusculature.
INTRODUCTION Stiassny and Schaefer, 2005; Schliewen and
Scha¨fer, 2006; Stiassny et al., 2006; Tshib-
The increased rate of species discovery and wabwaetal.,2006).Asspeciesdiscoveryrates
description in the Congolese cichlid genus increase, a concomitant understanding of
Nanochromis Pellegrin (see Lamboj, 2005; phylogenetic relationships is necessary to pro-
Schliewen and Stiassny, 2006; Lamboj and vide a framework for investigation of the
Schelly, 2006) is typical of a growing docu- mechanismsandprocessesunderlyingcontem-
mentation of the high levels of species di- porary aquatic diversity. To date, eleven
versity among freshwater fishes in the Congo Nanochromis species have been described,
River basin (Schelly and Stiassny, 2004; and a number of additional taxa are awaiting
1Division of Vertebrate Zoology, Department of Ichthyology, American Museum of Natural History, (mljs@amnh.
org).
2DepartmentofIchthyology,BavarianStateCollectionofZoology,Mu¨nchhausenstr.21,D-81247Mu¨nchen,Germany
([email protected]).
CopyrightEAmericanMuseumofNaturalHistory2007 ISSN0003-0082
2 AMERICAN MUSEUMNOVITATES NO. 3576
formal description (Schliewen and Stiassny, Comparative material comprised formalin-
2006, personal obs.; Lamboj, in litt.). In fixed specimens stored in 70–75% ethanol,
a recent study, Schliewen and Stiassny (2006) nonformalin-fixed specimens stored in 70–
discussed the presence of two informally 95% ethanol, and specimens cleared and
namedgroupswithinNanochromis:anudiceps stainedforboneandcartilageusingamodified
group and a squamiceps group. Both groups protocol based on Taylor and Van Dyke
are diagnosable on the basis of derived (1985).Whensufficientmaterialwasavailable,
anatomical features, and herein we restrict multiple cleared-and-stained specimens were
the genus Nanochromis s.str. to include the prepared and examined for each species.
typespeciesN.nudiceps(Boulenger,1899)and Institutional abbreviations follow Leviton et
seven congeners: N. consortus Roberts and al. (1985). The following comparative materi-
Stewart, 1976, N. minor Roberts and Stewart, als have been included in the study (values
1976,N.parilusRobertsandStewart,1976,N. after catalog number indicate number of
splendens Roberts and Stewart, 1976, N. specimens examined, and do not necessarily
teugelsi Lamboj and Schelly, 2006, N. trans- correspond to the total number of specimens
vestitus Stewart and Roberts, 1984, and N. in the lot; C&S indicates cleared-and-stained
wickleri Schliewen and Stiassny, 2006. The preparation; SL, standard length; HL, head
species of the squamiceps group are herein length):
formally recognized as members of the new Benitochromis finleyi: AMNH 238254, 1 ex.
genus, Congochromis, with C. squamiceps C&S, Cameroon.
(Boulenger, 1902) as the type species, along Benitochromis riomuniensis: CU 90064, 15 ex.,
withC.dimidiatus(Pellegrin,1900),C.sabinae Lobe River, Cameroon.
(Lamboj, 2005), and a new species from the Chromidotilapiamamonekenei:AMNH232367,
vicinity of Kisangani on the upper Congo 14 ex., 1 C&S, 27 km from Tchibanga,
River described herein. Gabon.
Chromidotilapia mrac: AMNH 229522, 5 ex.,
1 C&S, Mikouma River, Moyen-Ogooue´,
MATERIALS AND METHODS
Gabon.
Counts and morphometric measurements Congochromis dimidiatus: MNHN 1892-0120,
follow Barel et al. (1977), with the following syntype, 1 ex., Bangui; MNHN 1892-0121,
exceptions:predorsallengthismeasuredasthe syntypes,3ex.,Bangui;MNHN1920-0194-
distance between the dorsal fin origin and 6,3ex.,Bangui;AMNH8150,3ex.,1C&S,
snout tip. Preanal length is measured as the Bangui River at Bangui.
distancebetweentheanalfinoriginandsnout Congochromis sabinae: AMNH 235651, para-
tip. Depth of the head is measured from the type, 1 ex., Loubi River, Likouala River
topoftheheadatmidorbittotheventraledge drainage; AMNH 235652, paratype, 1 ex.,
of the interopercle. Measurements were re- Loubi River, Likouala River drainage;
corded to the nearest 0.1 mm using digital or AMNH 227666, 1 ex., Lossi Creek,
dial calipers. Vertebral counts exclude the Sangha River drainage; CU 88552, 1 ex.,
terminal, hypural-bearing vertebra, and verte- Mambili River, Likouala River drainage.
bral and fin spine/ray counts and measure- Congochromis squamiceps: BMNH 1902.4.14:
ments were obtained from radiographs or 11, syntype, 1 ex., Lindi River, Upper
cleared-and-stained skeletal preparations. Congo; IRSNB 13, syntype, 1 ex., Lindi
The terminal dorsal and anal soft fin rays River,UpperCongo;AMNH225399,1ex.,
are counted as single elements, even if Kisangani(Stanleyville),UpperCongo.
branched and split to the fin base when the Divandu albimarginatus: AMNH 232347, 4
element is associated with a single supporting ex., Onoy River at Bandi, Gabon.
pterygiophore. Gill raker counts correspond Nanochromisconsortus:AMNH233375,1ex.,
to the lower limb of the first arch and include Nziya,Congo River; AMNH236667, 1 ex.,
the raker in the angle of the arch marking the Nziya, Congo River; MCZ 50552, para-
transition from ceratobranchial to epibran- types, 5 ex., 1 C&S, mainstream Congo
chial. River, near Inga.
2007 STIASSNY AND SCHLIEWEN: NEW CICHLIDFROM CONGO 3
Nanochromis minor: AMNH 237660, 1 ex. Congochromis, we have performed an explor-
C&S., 2 km upstream of Kinganga, Congo atory multivariate analysis of 16 log-trans-
River; MCZ 50342, paratypes, 2 ex., main- formedmorphometricvariablesusingasheared
stream Congo River, downstream from principal components analysis (PCA) (Hum-
Kinganga. phries et al., 1981; Bookstein et al., 1985).
Nanochromis nudiceps: MRAC 1045, lecto- Principal components were factored from the
type, Kutu. covariancematrixoflog-transformedvariables.
Nanochromis parilus: MCZ 50202, paratypes, The PCA was conducted in Sheared PCA,
8 ex., 1 C&S, mainstream Congo River, a freeware program written for the Macintosh
near Wombe. operating system by Norman Macleod and
Nanochromis splendens: MCZ 50477, para- available for download at http://www.nhm.ac.
types, 6 ex., 1 C&S, mainstream Congo uk/hosted_sites/paleonet/ftp/ftp.html.
River, near Inga.
Nanochromis transvestitus: ZSM 29705, 9 ex., GENERIC DIAGNOSES
2 C&S, Lake Mai Ndombe, near Inongo.
In the following generic diagnoses and
Nanochromis teugelsi: AMNH 233374, para-
accompanying illustrations an asterisk pre-
type, 1 ex., Bandundu province, Bokoni
cedes character numbers, and character states
village, Kasai River, estuary across river.
are indicated by superscript numerals. Based
Nanochromis wickleri: AMNH 236666, para-
on outgroup comparison among other chro-
type, 1 ex. C&S, Lake Mai Ndombe at
midotilapiines and related cichlid species the
Inongo; AMNH 236665, paratype, 1 ex.,
use of superscript ‘‘1’’ indicates the hypothe-
Lake Mai Ndombe at Inongo.
sized derived state and superscript ‘‘0’’ the
Nanochromis sp.: AMNH 233569, 1 ex.,
plesiomorphicstateforeachfiguredcharacter.
Bobongo Creek into Sangha, Central
African Republic.
Parananochromis gabonicus: CU 80730, 1 ex. Nanochromis Pellegrin, 1904
C&S, Minka Creek, 7 km south of Oyem,
Gabon; AMNH 211142, 4 ex., Nye River, Type species: Nanochromis nudiceps (Boulenger, 1899)
Woleu-Ntem, Gabon. [Typelocality:Kutu,LakeLeopoldII,Zaire(LakeMai
Ndombe,DemocraticRepublicofCongo)].
Parananochromislongirostris:AMNH230708,
Includedspecies:N.consortusRobertsandStewart,1976,
7 ex., 1 C&S, Ivindo River, Gabon. N.minorRobertsandStewart,1976,N.parilusRoberts
Pelvicachromis humilis: AMNH 22238, 1 ex. andStewart,1976,N. splendens RobertsandStewart,
C&S, River Moa, Sierra Leone. 1976, N. teugelsi Lamboj and Schelly, 2006, N.
transvestitusStewartandRoberts,1984,andN.wickleri
Pelvicachromis taeniatus: AMNH 216147, 1
SchliewenandStiassny,2006.
ex. C&S, no data; CU 90064, 10 ex., Lobe
Nanochromis is diagnosed by the following
River, Cameroon.
combination of apomorphic features: at least
Teleogramma brichardi: MCZ 48009, 1 ex. the posterior half of the upper lateral line
C&S, Congo River, rapids at Kinsuka. contiguous with the dorsal-fin base; presence
Thysochromis ansorgii: AMNH 235828, 2 ex., of an asquamate nape, cheek, and belly;
Benin;AMNH216147,1ex.C&S,nodata. absence of a supraneural bone; possession of
Throughout this paper the phylogenetic extremely fine, closely spaced unicuspid teeth
speciesconceptisadoptedasabasisforspecies in upper and lower jaws (fig. 1, *11 vs. *10);
diagnosis. Congolese place names follow con- presence of a horizontally oriented, elongate
temporary usage, and equivalent colonial-era second infraorbital (fig. 1, *21 vs. *20).
placenamespreviouslyutilizedintheliterature Nanochromis shares with Congochromis, its
aregivenwithinbracketsfollowingtheirinitial putative sistergroup, the apomorphic features
appearanceinthebodyofthetext. of an elevated lateral line that is at least
partially contiguous with the dorsal fin (less
PRINCIPAL COMPONENTS ANALYSIS extensivelysoinCongochromis),acharacteris-
tic reduction of the infraorbital series consist-
To investigate species boundaries between ing of a single, elongate element behind the
the morphologically similar members of first infraorbital (preorbital) (figs. 1, 5A), and
4 AMERICAN MUSEUMNOVITATES NO. 3576
Fig. 1. Isolated infraorbitalseries, oral jaws, andsuspensoria of(A) Congochromis dimidiatus, AMNH
8150, (B)Nanochromis parilus,MCZ50202, and (C)Nanochromis minor, AMNH237660.
an exoccipital contribution to the ventral Included species: C. dimidiatus (Pellegrin, 1900), C.
articular surface of the pharyngeal apophysis. sabinae(Lamboj,2005),C.pugnatus,n.sp.
Congochromisisdiagnosedbythefollowing
combination of apomorphic features: four
Congochromis, new genus
pores in the dentary laterosensory canal
(fig. 1, *31 vs. five pores, *30), absence of
Typespecies:Congochromissquamiceps(Boulenger,1902)
a laterosensory canal in the angulo-articular
[Typelocality:Lindi,LindiRiver,UpperCongo,Zaire
(DemocraticRepublicofCongo)]. (fig. 1, *41 vs. *40), and six pores in the
2007 STIASSNY AND SCHLIEWEN: NEW CICHLIDFROM CONGO 5
Fig. 2. Caudal fin skeleton of (A) Parananochromis gabonicus (CU 80730), (B) Nanochromis parilus
(MCZ50202),(C)Congochromispugnatus(AMNH237670),(D)C.squamiceps(recordedfromaradiograph
of IRSNB 13), (E) C. sabinae (recorded from radiographs of AMNH 235651-2), and (F) C. dimidiatus
(AMNH 8150).
preopercle laterosensory canal (fig. 1, *51 vs. halfoftheupperlaterallinecontiguous);fully
seven pores, *50). scaled nape, and partially scaled chest and
The following combination of features cheek (vs. an asquamate nape, chest, and
distinguishes Congochromis from Nanochr- cheek); jaw teeth relatively robust unicuspids,
omis: only the last three to five pored scales not closely spaced (vs. extremely fine, closely
of the upper lateral line are contiguous with spaced unicuspids); and the presence of
the dorsal-fin base (vs. at least the posterior a small, supraneural bone (vs. absence).
6 AMERICAN MUSEUMNOVITATES NO. 3576
insertion. Head short (length 31.2–33.2%,
mean 32.1% SL) and deep (depth 21.2–
25.1%, 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 toshort, deep caudal
peduncle. Ventral body profile more or less
straight (males) or strongly convex (females).
Flanks covered with large, regularly imbri-
Fig. 3. Head squamation of Congochromis cating,cycloidscales.Afewdeeplyembedded,
pugnatus (paratype, AMNH 237670); gray area on cycloid scales scattered over opercle and
cheek indicates region of expanded adductor man-
subopercle. Cheek with small round, cycloid
dibulaemusculature.
scales restricted to one or two rows at
dorsoposterior margin. Occipital region with
Congochromis pugnatus, new species
numerous small, imbricating cycloid scales to
figures 3–5 level of midorbit. Small cycloid scales over
pectoral-fin base, chest naked. Belly scales
HOLOTYPE: AMNH 6079, 48.2 mm SL, slightly smaller with a gradual transition in
adult male, Democratic Republic of Congo, size; scales on ventral portion of belly and
Kisangani (Stanleyville), H. Lang and J.P. anal-genitalregionofsamesizeaslateralbelly
Chapin, May 1915. scales. Upper lateral line originates behind
PARATYPES: Eight paratypes with same occipital margin of opercle, ascends gradually
data as holotype: AMNH 237670, 2 ex., 1 to dorsal-fin base reaching highest point at
C&S, 37.0–51.5 mm SL; FMNH 57121, 3 ex., levelof10thto12thdorsalfinspine,continues
37.8–49.1 mm SL; MRAC 2006-45-P-1, with half an intervening scale or no interven-
50.4 mm SL; ZSM 34981, 2 ex., 37.0– ing scale between lateral line and dorsal-fin
49.2 mm SL. base. Pored scales interspersed with more
DIAGNOSIS: A Congochromis diagnosed by numerous nonpored scales along length of
thepossessionofacompoundurostyle+fused upper lateral line. Lower lateral line short,
hypural plate (fig. 2C). Further differs from usually consisting of only two or three pored
all congeners in possessing a strongly inclined scales interspersed among nonpored scales.
lower jaw and expanded cheek musculature Upperlaterallineseparatedfromlowerlateral
(fig. 3). line by two scales (excluding pored rows).
DESCRIPTION: Based on the holotype and Caudal-finbasewithasinglelargeporedscale
eight paratypes. See table 1 for a summary of medially (not included in longitudinal scale
morphometric and meristic data for the new count) and numerous small scales over basal
taxon and for comparative data on type eighth of fin.
specimens of all congeners. Morphological Dorsal fin with XVI–XVIII (mode XVII)
characteristics and general pigmentation pat- spinesand6–9(mode8)rays.AnalfinwithIII
tern can be observed in figure 4, and of spines and 5–6 (mode 6) soft rays. Dorsal-fin
congeners in figure 6. A robust, relatively spines gradually increase in length to 14th or
deep-bodied species (depth 29.3–35.5%, mean 15th spine, remaining spines of equal length.
31.7%SL).Greatestbodydepthat(males),or Soft dorsal and anal fins in males with
slightly behind (females), level of pelvic-fin tapering filamentous extensions reaching to
2007 STIASSNY AND SCHLIEWEN: NEW CICHLIDFROM CONGO 7
Largest naeH 3565237.0 32.133.540.346.814.663.239.532.275.4 35.518.916.931.531.520.2 28 XVIII 861125
ps,Two C.sabiAMN 35651248.0 29.631.347.352.015.260.436.731.258.1 34.021.719.339.332.021.3 26 XVII 851024
e 2
c
mi
C.squa atusN 92–12129.0 33.129.344.751.815.961.450.631.770.0 22.417.014.134.124.718.8 27 XVII 76925
of midiNH
Syntypes C.diM 92–12044.5 29.028.552.753.515.761.840.232.675.1 26.019.614.236.229.120.5 26 XVII 76-ve25
o
w
T
atus,n.sp.,C.sabinae miceps BMNH 1902.4.14:1138.9 28.830.8-ve-ve15.257.140.828.267.8 30.0-ve17.537.529.225.8 XVII 87827
gnof ua
pues sq
omisratyp C. SNB 37.5 9.74.05.82.67.34.04.40.90.3 2.12.57.30.77.17.8 5 VIII 8686
ra R 14 233416437 321422 2 X 2
chP I
oo
1gw
TABLEofConandT SD 1.820.815.754.110.821.711.571.454.79 1.701.410.772.271.261.37
atypesdiatus, Max 51.5 35.533.251.757.218.365.445.132.872.5 33.325.117.441.230.628.8
armi
Pdi
dEightsofC. us,n.sp. Min 33.8 29.331.236.045.015.660.439.928.857.4 28.621.215.034.526.924.4
ypeanyntype pugnat Mean 31.732.143.849.317.462.742.430.968.6 30.923.116.338.728.526.2
atafortheHolotS Congochromis N 9 888888888 888888 26(1),27(4),28(3)XVI(2),XVII(4),XVIII(2)6(1),8(6),9(1)5(1),6(7)8(1),9(5),10(2)26(7),27(1)
D
c e
risti otyp 8.2 2.21.50.05.08.05.41.31.71.6 1.35.15.08.80.66.9 5 VIII 8697
Me Hol 4 334416437 321332 2 X 2
d
n
a
Morphometric Character SL %SLBodydepthHeadlengthCplengthCpdepthAnalbaseDorsalbasePostorb.lengthPredorsalPreanal %HLSnLHeaddepthPreorb,lengthLjlengthOrbitalwidthCheekdepth CountsLongitud.scales Dorsalspines DorsalraysAnalraysGillrakersVertebrae
8 AMERICAN MUSEUMNOVITATES NO. 3576
Fig.4. Congochromispugnatus:(A)AMNH6079,holotype,male,48.2 mmSL,DemocraticRepublicof
Congo,Kisangani(Stanleyville),May1915,H.LangandJ.P.Chapin;(B)AMNH237670,paratype,female,
37.0 mm SL,same dataasholotype.
basalthirdofcaudalfin.Infemalessoftdorsal Outerrowdentitiononbothpremaxillaand
and anal fins are pointed but not produced dentary composed of relatively robust, re-
and do not reach base of caudal fin. Caudal curved, unicuspid teeth (fig. 5B). Teeth are
fin rounded with 14 branched rays; appears evenly spaced along each jaw, three or four
lance-shaped, subacuminate when adducted. symphysial teeth on dentary somewhat en-
First pelvic fin ray longest in both sexes, larged and procumbently implanted.
reaching anal fin base in males, shorter in Anteriorly in both jaws three to four short
females. Pectoral fin rounded, reaching verti- inner rows of recurved teeth taper to a single
cal approximately at midpoint of spinous row posteriorly.
dorsal fin. Lower pharyngeal jaw (fig. 5D) relatively
Eightto10smallgillrakersalongouterrow gracile, with narrow horns and a short blunt
oflowerlimboffirstgillarch(includinglarger keel. Dentigerous surface sparsely covered
more elongate raker in angle of arch) and with bicuspid teeth. Posterior row teeth
three to five bulbous epibranchial rakers elongate, erect, closely spaced bicuspids with
(fig. 5C). In common with most other chro- strongly hooked major cusp and smaller
midotilapiine cichlids, a prominent visorlike, minor cusp. Anteriorly lower pharyngeal jaw
hanging pharyngeal pad is developed on teeth weakly erect, somewhat shouldered,
epibranchial 2, and no microbranchiospines robust, unicuspids.
are present on outer face of second, third, or Vertebrae column with a total of 26–27
fourth gill arches. (mode 26) vertebrae.
2007 STIASSNY AND SCHLIEWEN: NEW CICHLIDFROM CONGO 9
Fig.5. Congochromispugnatus,AMNH237670,paratype,male,51.5 mmSL:(A)infraorbitalseries,(B)
suspensorium andjaws, (C) 1stgillarch, and(D)lower pharyngealjaw.
MISCELLANEOUS OSTEOLOGY AND ANAT- of five separate hypural elements, each of
OMY: In common with other Congochromis, whicharticulateswithanautogenousterminal
the first infraorbital of C. pugnatus has four urostyle (e.g., fig. 2A, B). In Congochromis
sensorycanalporesandisfollowedbyasingle, variouspatternsofhypuralfusionsareevident
elongate, dorsoposteriorly oriented infraorbi- (e.g., fig. 2C–F), but uniquely in C. pugnatus
talelement(fig. 5A).Fourporesperforatethe hypurals 1+2 and 3+4 are fused into a single
laterosensory canal in the dentary, the angu- element, and the resultant compound hypural
loarticular lacks a canal, and six pores plateisfusedwiththeurostyle(fig. 2C);thisis
perforate the preopercular canal (fig. 5B). the case even in the smallest specimens
The pharyngeal apophysis has an extensive examined. By contrast, C. sabinae (fig. 2E),
exoccipital contribution to the ventral articu- C. squamiceps (fig. 2D), and C. dimidiatus
lar surface of the apophysis. (fig. 2F) have hypurals 3+4 (or 3 and 4 in the
Primitively in the caudal skeleton of chro- case of C. dimidiatus) fused with the urostyle,
midotilapiines the hypural plate is comprised but hypurals 1+2 (C. sabinae) or hypurals 1
10 AMERICAN MUSEUMNOVITATES NO. 3576
Fig. 6. (A) Congochromis squamiceps, IRSNB 13, syntype, male, 47.5 mm SL, Lindi River, Upper
Congo,(B)C.dimidiatus,MNHN1892-0120,syntype,male,44.5 mmSL,Bangui,(C)C.sabinae,AMNH
235651,paratype,male, 48.0mm SL, Loubi River,southwest ofMakoua.
and 2 (C. squamiceps and C. dimidiatus) COLORATIONINPRESERVATIVE(fig.4): Ground
remain autogenous, even in the largest speci- color is more or less uniformly pale brown.
mens available for study. In C. pugnatus the Specimens have been in preservative for more
adductor mandibulae muscle is well devel- than 90 years and pigmentation is faded;
oped, and in large individuals the anterioven- nonetheless, each flank scale has a narrow
tral portion ofthe musclecomplexisenlarged pigmented bar on its exposed posterior edge.
andvoluminous,lendingacharacteristicbulge Scale centers retain traces of a silvery irides-
to the cheek (fig. 3). cence, and this silvery iridescence is most