Mormyrus rume Valenciennes, 1846
Species overview
Large fish, body moderately elongate, head with funnel-shaped snout (tubular-snouted), mouth terminal with protruding lower lip. No conspicuous cutaneous sensory organs below the eye (but see below). Pectoral fin not extending to pelvic fin. Countershaded. Size observed: 870 mm SL, 5300 g.
M. rume(measurements)
Taxonomic description
-Body moderately elongate, laterally compressed, cross section oblong-oval, body depth 21-31 % SL, greatest depth at origin of dorsal fin.
-Head length 23-28 % SL; head depth 15-22 % SL, 70-81 % body depth.
-Outline of back in front of dorsal fin convex, at base of D feebly convex, upper profile of head more or less straight or to feebly concave, underside of head concave, outline of belly, base of anal fin inclusive, slightly convex, no step at base of pelvic fin.
-Snout funnel-shape, pointed, 38-45 % head length, 70-88 % postorbital length.
-Mouth 9-13 % head length, terminal, with thick lips and protruding lower lip, edge of mouth far away from anterior nostril, edge of upper jaw on a level with upper edge base of pectoral fin.
-Chin with moderate submental swelling, lower jaw about as deep as upper part of snout.
-Teeth notched, 3-9/6-14.
-Nostrils separate, circular or oval, anterior nostril on a level with centre of eye, distance between nostrils 7-15 % length of snout, distance from eye 22-32 % length of snout, axis of nostrils makes an angle of 60° to axis of head.
-Eye diameter 11-18 % head length, 20-38 % postorbital length; orbital cavity oval. No conspicuous tuberous organs below the eye.
-Opercular cleft curved, 33-49 % head length, 48-55 % head depth.
-Dorsal fin 72-95 fin-rays, base of D 53-60 % SL, anal fin 16-21 rays, base of A 9-15 % SL, origin of D far before origin of A, about halfway between bases of pectoral and pelvic fin, end of D far behind end of A; predorsal length 31-36 % SL, preanal length 57-67 % SL.
-Pectoral fin obtusely pointed, extending to about 2/3 the distance to pelvic fin, its origin at lower edge of opercular cleft. V is slightly closer to P than to A..
-Caudal fin obtusely pointed to rounded, the scaled lobes obtusely pointed, covering about 3/4 of the entire fin. 92-115 scales in lateral line; 20-26 round caudal peduncle.
-Caudal peduncle 6-13 % SL, its depth 4-6 % SL, 38-72 % its length.
-Coloration »Generally silvery, back darker, from greenish- or yellowish-grey to blackish, belly white or grey but always a little lighter than the back«. Countershaded.
Type locality
»Riv. Sénégal«.
Distribution
Chad, Benue, Niger, Volta Gambia and Senegal basins and some coastal basins of Ivory Coast: Cavally, Bandama and Comoe; Mono and Ueme, Benin; Ogun and Culufi, Nigeria.
Electric organ discharges
Biphasic, head positive, +/–
Total duration 0.966 " 0.109 msec, n = 9, (not significantly different from the EOD of Mormyrus subundulatus, see there.) Conductivity 66-129 µS, pH 6.8-7.1 in natural environment.
Ratio total voltage / voltage phase 2 (– ) 1.441 (range 1.318-1,5).
M. rume(EOD)