Pollimyrus isidori isidori (Valenciennes, 1846)
Species overview
Small fish, body short and stout, moderately deep, head about as long as deep, snout short, rounded, slightly protruding mouth; caudal fin obtusely pointed.; coloration varies with localities, silvery all over or with numerous melanophores on head, back and/or flanks. Size observed: 89 mm SL. P. i. isidori(measurement)
Taxonomic description
-Body short, moderately deep, strongly laterally compressed, body depth 27-35 % SL, greatest depth more or less at middle of body.
-Head length 23-28 % SL; head depth 22-28 % SL, 72-84 % body depth.
-Outline of back slightly convex to straight, upper profile of head strongly convex, rarely rather straight, underside of head convex, outline of belly slightly convex, bases of unpaired fins more or less steeply running to caudal peduncle.
-Snout strongly rounded, 12-20 % head length, 19-36 % postorbital length.
-Mouth 16-23 % head length, slightly subterminal, its edge extending to a line below posterior nostril, which is close to anterior rim of eye, upper jaw on a level with upper edge base of pectoral fin.
-Chin inconspicuous.
-Teeth notched, 5-8/6-10.
-Nostrils separate, circular, anterior nostril on a level with centre of eye, posterior nostril on a level above lower rim of eye. The axis of the nostrils cutting axis of head at an angle of about 45°.
-Eye diameter 14-24 % head length, 24-43 % postorbital length. Opercular cleft strongly curved, its posterior margin not or slightly extending beyond base of pectoral fin, 21-43 % head length, 28-40 % head depth.
-Dorsal fin 17-22 fin-rays, base of D 18-23 % SL, anal fin 21-27 rays, base of A 22-27 % SL, origin of D behind origin of A, end of D more or less opposite end of A; predorsal length 56-62 % SL, preanal length 53-60 % SL.
-Pectoral fin pointed, extending to tip of pelvic fin. V is closer to P than to A.
-Caudal fin obtusely pointed, the scaled lobes are short and rounded. 45-64 scales in lateral line; 14-18 round caudal peduncle, depending on area of distribution.
-Caudal peduncle 18-25 % SL, its depth 6-7 % SL, 24-35 % its length.
-Coloration varying with habitat; populations from central regions of a stream are silvery with numerous small melanophores on the body, in particular on the head and the upper parts of the trunk, populations living more upstream are generally much darker with much more extended melanophores.
Type locality
P. isidori »Nil (Egypte)«; M. gaillardi »Bol (Lac Tchad, 13° 30 ‘ N 14° 41 ‘ E)«; M. rudebeckii »Boroba Swamp, Gambia River, MacCarthy Island«, Senegal; P. lhuysi (non Steindachner, 1870) Daget, 1954 »Niger supérieur«.
Distribution
Widely distributed, from Gambia, Senegal, Middle Niger, Benue, Lake Chad, the Volta rivers, coastal rivers of Ivory Coast (Sassandra (4° 48 ‘ N 6° 05 ‘ W), Bandama (5° 10 ‘ N 4° 58 ‘ W), Mé).
Electric organ discharges
Biphasic, head positive, +/– , rather long, with a small spike in the positive phase.
P. isidori(EOD)