Petrocephalus soudanensis Bigorne and Paugy, 1991
Species overview
Small fish, body moderately short and deep, head longer than deep, snout short, eye large, mouth inferior. Particular aggregations of cutaneous sensory organs not indicated. A black spot beneath the first, also black, rays of the dorsal fin, Upper and lower rays of caudal fin black. Size observed: 87 mm SL, 115 mm TL.
P. soudanensis(measurements)
Taxonomic description
-Body moderately short, strongly laterally compressed, body depth 32-36 % SL, greatest depth between pelvic and anal fin.
-Head length 25-28 % SL; head depth not indicated.
-Outline of back slightly convex, profile of head parabolic, outline of belly slightly convex, bases of unpaired fins steeply running to caudal peduncle.
-Snout rounded, short, 15-18 % head length.
-Mouth small, inferior, its edge below anterior rim of lens, upper jaw on a level with upper edge base of pectoral fin.
-Chin inconspicuous.
-Teeth small, notched, 7-12 in upper jaw, 14-23 in lower, depending on the size of the specimen.
-Nostrils closely together, upright-oblong, on a level with lower rim of the eye, axis parallel to axis of head.
-Eye big, diameter 29-35 % head length. Presence or absence of particular aggregations of electrorecpetors on the head not indicated.
-Opercular cleft strongly curved, length not indicated.
-Dorsal fin 24-29 fin-rays, base of D 19-23 % SL, anal fin 29-35 rays, base of A 29-31 % SL, origin of D behind origin of A, end of D well before end of A; predorsal length 58-64 % SL, preanal length 55-60 % SL.
-Pectoral fin pointed, extending beyond middle of pelvic fin. V is closer to P than to A.
-Caudal fin pointed, scaled part short. 37-42 scales in lateral line; 12 round caudal peduncle.
-Caudal peduncle short, 15-17 % SL, its depth 5-6 % SL, 33-37 % its length. (Data based on original description).
-Coloration Silvery. »A black, oblong, vertical spot below the base the first rays of the dorsal fin which are also black, so are the dorsal and ventral most rays of the caudal fin which form a V-shaped marking«.
Type locality
»Guinée, Niandan à Loutou«. (Niandan, tributary of the upper Niger river, 10° 35 ‘ N 09° 45 ‘ W.)
Distribution
Upper Niger, approximately from the central delta up to the upper Guinean tributaries; Benue river and lower Niger. Also in the Chad basin and in the Volta river.
Electric organ discharges
Triphasic, head positive, +/– /+
Duration from beginning to peak of negative phase:9-15 µsec
Total duration of negative phase:25-30 µsec
No sexual differences (Graff and Bigorne, 1990)