Hippopotamyrus castor Pappenheim, 1906
Species overview
-Body moderately deep, snout short, blunt, head round-snouted, mouth subterminal, D and A nearly equal in length, their margins clearly convex; dark band between D and A, on anterior parts of D and A and on longest rays of caudal fin. Size observed: 200 mm SL, 235 mm TL.
H. castor(measurements)
Taxonomic description
-Body moderately deep, 22-25 % SL, greatest depth close to D; head about as long as body depth, length of head 22-26 % SL, head depth 19-12 % SL, 68-80 % body depth.
-Outline of back slightly convex, smoothly continuing into upper profile of head which is convex, underside of head concave, outline of belly slightly convex.
-Snout rounded, protruding mouth, snout length 25-30 % length of head.
-Mouth subterminal, its edge below anterior rim of eye; upper jaw on a level with lower edge opercular cleft.
-Chin with moderate submental swelling.
-Teeth notched or truncate when worn down, 5/6, the median pair in lower jaw much larger than the others.
-Nostrils circular, positioned below level of eye, distance between nostrils 16 - 22 % snout length, posterior one 33-50 % snout length away from eye; axis of nostrils runs more or less parallel to axis of head.
-Eye circular or suboval, 15-20 % length of head, about 1/2 its diameter away from front.
-Opercular cleft curved, about 30 % length of head, 38-42 % head depth.
-Dorsal fin 31-33 fin-rays, its base 17-27 % SL, anal fin 30-35 rays, its base 24-27 % SL, D originating and ending more or less opposite to origin and end of A, respectively; predorsal length 57-62 % SL, preanal length 57-60 % SL.
-Pectoral fin short, pointed or obtusely pointed, extends beyond base of pelvic fin which is closer to P than to A.
-Caudal fin pointed, both membranes and scaled lobes which extend to 1/2 its length. Lateral line 77-93 scales, 16 round caudal peduncle.
-Caudal peduncle 17-26 % SL, its depth 4-5 % SL, 17-28 % its length.
Coloration: body uniform dark brown with one or two blackish bands between origin of D and A, first part on D and A black, also basal parts of these fins as well as of C, and longest rays of C.
Type locality
H. castor: »Lokundje bei Bipindi, (Kamerun)« (03° 10 ‘ N 11° 30 ‘ E); P. aequipinnis: »Nanga Eboko (Sanaga)«
(00° 41 ‘ N 12° 22 ‘ E).
Distribution
Sanaga and Lokundje rivers, Cameroon.