Mormyrus longirostris Peters, 1852
Species overview
Large fish, body moderately elongate, rather deep, head tapering into a trunk-like snout, slightly bent downwards, mouth terminal. Two conspicuous cutaneous sensory organs below the eye. Caudal peduncle rather deep. Back dark, belly whitish, countershaded. Size observed: 417 mm TL.
M. longirostris(measurements)
Taxonomic description
-Body moderately elongate, laterally compressed, cross section oblong-oval, body depth 21 % SL, greatest depth near origin of dorsal fin.
-Head length 26 % SL; head depth 14 % SL, 67 % body depth.
-Outline of back (dorsal fin inclusive) slightly convex, upper profile of head concave or nearly straight, sloping; underside of head concave; outline of belly (anal fin inclusive) curved.
-Snout funnel-shaped, tapering into a tube*, 45 % head length, 91 % postorbital length.
-Mouth terminal, 9 % head length, 21% snouth length, edge of mouth far away from anterior nostril, edge of upper jaw on a level with underside of head.
-Chin without appendage, mandible deeper than upper part of snout, slightly protruding.
-Teeth notched, 5-7/8-12.
-Nostrils separate, posterior one slightly oval, anterior nostril on a level slightly below rim of eye, posterior nostril slightly below anterior, distance between nostrils about half their distance from eye, their axis cutting axis of head at an angle of about 45°.
-Eye small, its diameter 9 % head length, 19 % postorbital length. Two conspicuous cutaneous sensory organs, suborbital tuberous organs, below the eye.
-Opercular cleft curved, 33 % length of head, 59 % depth of head.
-Dorsal fin 65-75 fin-rays, base of D 46 % SL, anal fin 17-19 rays, base of A 11 % SL, origin of D very far anterior to origin of A, almost halfway between pectoral and pelvic fin, end of D far posterior end of A; predorsal length 42 % SL, preanal length 60 % SL.
-Pectoral fin obtusely pointed, extending to middle between pectoral and pelvic fin. V is about equally distant from P and A.
-Caudal fin obtusely pointed, the scaled lobes covering about 3/4 of the entire fin. 88-100 scales in lateral line; 22-28 round caudal peduncle.
-Caudal peduncle 13 % SL, its depth 7 % SL, 49 % its length.
The proportions refer to the syntype ZMB 3672, in the other syntype (ZMB 3671) the snout is badly damaged so that no standard length can be taken. The other museum specimens do not show suborbital tuberous organs.
*) The extreme shape of the snout changes with age/size of the fish, in juveniles it is much less obvious.
-Coloration, olive brown above, whitish or silvery below, countershaded.
Type locality
M. longirostris: »Zambeze«
Distribution
»Lower and Middle Zambezi River, Lower Sabi (21° 00 ‘ S 35° 02 ‘ E) and Lundi Rivers (21° 19 ‘ S 32° 24 ‘ E), Lakes Nyasa (Malawi) (12° 00 ‘ S °34 30 ‘ E), Rukwa (7° 00 ‘ S 31° 20 ‘ E), Tanganyika (6° 00 ‘ S 29° 30 ‘ E). Luapula (9° 26’ S 28° 33 ‘ E)-Moero (9° 00 ‘ S 28° 45 ‘ E)-Bangwelo (11° 30 ‘ S 30° 15 ‘ E) system. Democratic Republic of Congo; Tanzania; Zambia; Zimbabwe; Mozambique; Malawi, respectively.