Diagnosis |
Diagnosis: recognized by its pointed snout, the rather small mouth, and the width of the premaxillary tooth plate (1/5-1/3.5, usually 1/4, of head length); vomerine dentition represented by a square to rectangular tooth plate which begins to develop at sizes between 60 and 70 mm standard length; palatine dentition developing at sizes over 100 mm standard length, initially as isolated teeth; second or third branched dorsal-fin ray always the longest; upper caudal-fin lobe much longer than lower lobe; gill rakers long and smooth; other characters, such as length of dorsal fin, number of branched rays in anal fin, and number of gill rakers on first gill arch, are subject to intraspecific variations; sexually mature males and (some) ripe females show considerable morphological differences; such specimens have often been labelled as Chrysichthys furcatus; maturity occurs probably at a rather advanced stage (at over 200 mm SL) and leads to the inflation of head, broadening of mouth and premaxillary tooth plate, shortening of spines and overgrowth of fin-spines by thick skin, the fins becoming more rounded, and the caudal-fin lobes sometimes becoming subequal; the body acquires an emaciated, thinned down appearance (Ref. 57126, 81642). Characters only clear in mature males in
reproduction: adipose fin short, base contained 8-11 times in SL and measuring 28-64% of distance between dorsal fin and adipose fin; maxillary barbel not reaching beyond dorsal spine when extended; head swollen; skin mucous; spines thick and covered with skin (Ref. 81642).
Description: nasal barbels present; very short first dorsal spine; well developed second spine, weakly denticulate along posterior margin; pelvic fin with 1 unbranched and 5 branched soft rays (Ref. 57126). Anal fin with 3-7 unbranched and 8-12 branched soft rays (Ref. 57126, 81642). Post-cleithral process well developed (Ref. 75075). In the Sanaga River (Cameroon), close to the Nachtigal waterfalls, the dorsal fin is very long (length 30-40% SL versus 15-30% normally); the species then resembles C. longidorsalis from which it is distinguished by its more pointed snout, the presence of vomerine teeth and a smaller occipital process (Ref. 81642).
Coloration: live specimens greyish-silvery, but may become black under stress; preserved specimens dark brown on head and back, and white on belly; adipose fin often blackish; black spot behind gill cover very distinct; fins black-edged (Ref. 57126, 81642). |