• View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Aquatic Commons THE A leA JOU L OF (Afr. J Trop. Hydrobiol. Fish) Yo. 1 1994 THE TAXONOMY OF THE GENUS SYNODONTIS (PISCES: SILUROIDEA) IN LAKE KAINJI, NIGERIA N.G. WIlLOUGHBY Kainji Research Project P.M.B. 666, New Bussa, Nigeria Present Address: Fisheries Research Ojjicer, Lower Shire, P/B Chiromo, Malawi ABSTRACT This paper considers the taxonomy of most of the Synodontis spp. present in the main drainage basins of West Mrica. The first section consists of a key to the sixteen species known to occur in Lake Kainji. Nigeria. A second section considers species which are reputed to live in the area and therefore might occur in the lake. It is suggested that several of the latter group are synonymous with better known species. INTRODUCTION (pers.comm.) consider thflt the differences Thispaperis concernedwith the taxonomy cited by Poll do notwarrant generic status, of a group of commercially important cat and thatsince there is little osteological data fishes in the recentlyformed man-made lake, to support it, this divisioN is notjustified. Lake Kainji, ontheRiverNigerinNigeria,West Consequentlythe original classification will Africa. be adhered to in the present work. Systematicswork on the genus Synodontis The key considers only those species startedwith BOULENGER's (1911) catalogue known to be present in Lake Kainji. Other ofthosespeciespresentin the BritishMuseum specieswhich, itis thought, mightoccur, are (NaturalHistory). Thetaxonomyofthe genus described later. Thus the majority of the has recently been revised by POLL (1971), species of Synodontis to be found in West who divided the genus into three genera, Africaare consideredin this paper. However, Synodontis, Hemisynodontis and for more extensive descriptionsand figures, Brachysynodontis, the last two ofwhich are the works of BOULENGER (1911), POLL monospecific. POLL (op. cit.) based this (1971),LEWIS (1974) and WILLOUGHBY division largel)'upon theextended opercular (1974) should be consulted. openings ofS. membranaceusand S. batensoda Synodontisare small to medium sized cat which he placed in Hemisyno-dontis and fishes (Figure 1). They have three pairs of Brachysynodontis respectively. However, well-developed barbels, the two mandibular the presentauthorand DrP.H. Greenwood pairs being branched.The head is enclosed of the British Museum (Natural History) in a heavy bony casing, the cephalo-nuchal 26 N.G. WllLOUGHBY shield. The first ray of the dorsal fin and of Key to the species of Synodontis recorded of each pectoral fin is modified to form a stout from Lake Kainji serrated spine, which can be locked at right 1.(a) No gap between end of rayed dorsal (b) H1 angles to the body axis. In addition to the fin and adipose fin. Ventral surface rid~ rayed dorsal fin, there is an adipose fin, often darker than dorsal surface in life. low ........................................................................2 l (b) Gap present between end of rayed (c) Hl dorsal and adipose fin. Dorsal surface will darker than ventral surface in life. and ........................................................................3 1.4­ 2. (a) 7-16 mandibular teeth. Wide black witt , membrane running full length of max­ illary barbel. Fins pale grey and DA( neve{, spotted.... .Synodontis 6. (a) 6-' ., membranaceus (GEOFFROY-ST.­ time HILAIRE 1809) (pOLL, 1971,placesthis don standard lenath species in the genus Hemisynodontis) Colc (b) 35-60 mandibular teeth. Membrane on maxillary barbel tapers from base to at tip. Caudal fin always spottedwithblack. (b) 15 ·1 ......................Synodontis batensoda 1.5t (RUPPELL 1832) (POLL, 1971, ond« places this species in the genus Colo Brachysynodontis) maxillary tooth band spot! mandibular tootl1 band (c) 53-78 mandibular teeth. Maxillary Be barbels with tubercles or small ramifi­ 7. (a) Sn ~~~ma"lIary barbe' maxil'ary barbel membrane cations anda narrow membrane restricted Eye . outer mandIbular barbel to basal third. inner mandIbular barbel lengl ...................................Synodontis (b) Snl t . resupinatus Eye« BOULENGER 1909 3. (a) Lower partofhumeral process bearing 8. (a) 12· spines Synodontis budgetti tusel BOULENGER 1911. (See also S. omias). gold4 (b) Lower part of humeral process not of e) bearing spines ~. cour, . 4 xiphi Fig. 1. Synodontis Measurements. 4. (a) Maxillary barbels bearing fine rami- (b) 24· fications. Caudal fin red..... .. Synodontis tusel: large, which lacks supporting bony rays. The clarias (LINNAEUS 1758) oliv skin is without scales, butmay havevilli, which (b) Maxillarybarbelsunbranched. Caudal are small hair-like projections from the body fin neverred 5 viol, wall into the over-lying mucous covering. 5. (a) Humeral process rounded with no S. s ridge along lower margin. Both lobes KEY TO WEST AFRICAN SYNODONTIS SSP 27 Synodontis recorded of caudal fin edged with black (c) 29-49 mandibular teeth. Snout large, ji ......................................................................6 depressed and rounded. Colour dark en end of rayed dorsal (b) Humeral process sharply pointed with brown with darker spots ofeye diameter e fin. Ventral surface ridge (sometimes not prominent) along size or smaller. orsal surface in life. lower margin ., Synodontis , 2 ..............................................7 gobroni DAGET 1954. See also S. between end of rayed (c) Humeral process obtusely pointed guttatus). lOse fin. Dorsal surface with n0 ridge along lower margin. Head 9. (a) 44-62 rnandibularteeth. Dorsal fin with entral surface in life, and body strongly compressed (height rays 1-5 prolonged into filaments. Colour ...........................................3 1.4-1.6 times width). Body covered olive to brown with small dark spots. ular teeth. Wide black with fine vernliculated spots. ...................................Synodontis ling full length of max- .................. ..Synodontis vermiculatus eupterus Fins pale grey and DAGET 1954. BOULENGER 1901 potted.... .Synodontis 6. (a) 6-9 mandibular teeth. Snout 1.8-2.1 (b) 23-43 mandibular teeth. Dorsal fin rs (GEOFFROY-ST.­ times post-orbital length. Filament on filaments absent or present on first ray ,(POLL,1971,placesthis dorsal spine shorter than spine. only 10 genus Hemisynodontis) Colour of body uniform grey. 1O.(a) Adipose fin small, approximately 25% mlarteeth. Membrane on ........................... ,.... .Synodontissorex of standard length. Colour mid to dark leI tapers from base to GUNTER 1864 brown with dark spots of less than eye ~ways spotted withblack. (b) 15-23 mandibular teeth. Snout 1.2- diameter size on body and fins. .Synodontis batensoda 1.5 times post-orbital length. Filament ...............................: Synodontis 1832) (POLL, 1971, on dorsal spine much longer than spine. nigrita CUVIERand VALENCIENNES ipecies in the genus Colour of body yellowish with dark 1940 (See also S. melanopterus.) ntis) spots Synodontisjilamentosus (b) Adipose fin medium sized, more than ibular teeth. Maxillary BOULENGER 1901 30%ofstandard length. Colour yellow, lbercles or small ramifi­ 7. (a) Snout 60% or more of head length. brown or olive, with or without spots. rrow membrane restricted Eye diameter less than 30% of snout ., 11 length. ll.(a) Body marked with dark spots larger ,.. , Synodontis (b) Snout 50% or less of head length. than eye diameter. Fins spotted or Eye diameter 30-70% ofsnout length. striped Syn 0 don tis ocellifer Rl909 .......................................................................9 BOULENGER 1900 'humeral process bearing 8. (a) 12-17 mandibular teeth. Snout ob- (b) Body and fins usually unspotted. .... ..Synodontis budgetti tusely pointed with fleshy lips. Colour Spots minute when present. 12 1911. (SeealsoS. omias). golden yellow with dark brown spots 12.(a) Mandibular tooth band less than half of humeral process not of eye diameter size. as wide as maxillary tooth band. Dorsal s ., ,", Synodontis ::" surface of pectoral spine usually more courteti PELLEGRIN 1906 (See also S. coarsely ridged than ventral surface. ....................... , 4 xiphias and S. labeo) Skin generally villose. Crest of rrbels bearing fine rami­ (b) 24-30 mandibular teeth. Snout ob- cephalonuchal shield immediately in lalfinred. ......Synodontis tusely pointedbutlips not fleshy. Colour front of dorsal spine obtusely pointed. AEUS 1758) olive to brown with no spots. ........................... " Synodontis rbels unbranched. Caudal ...................................... .Synodontis schall BLOCH-SCHNEIDER 1801 (See ............ , , 5 violaceus PELLEGRIN 1919 (See also also S. robbianus). ocess rounded with no S. solani). (b) Mandibular tooth band more than half lwer margin. Both lobes as wide as maxillary tooth band. Dorsal 28 N.G.WIl.LOUGHBY surface of pectoral spine wi th ridges and it is unlikely that the two belong to the Synodont ofsamesize as on ventralsurface. Skin same species. S. xiphias closely resembles S. This: seldom bearing any villossities. Crest counetiin body proportions, barbel lengths, violaceus ofcephalonuchalshield immediately the humeral process, and also in the pos­ RiverNi! in front ofdorsal spine rounded. session of a flap of skin running longi­ KainjibyI ....................................Synodontis tudinally between the inner mandibular byLELE: gambiensisGUNTHER 1864 barbels. S. couneti is the only West African unlikeaI Description ofSynodontisspp. reputed to occur Synodontis known to possess this flap, and areaofth in or near Lake Kainji: thus the