Cromeria occidentalis Daget, 1954
photo by MNHN

Family:  Kneriidae (Shellears), subfamily: Kneriinae
Max. size:  4.4 cm SL (male/unsexed)
Environment:  benthopelagic; freshwater; pH range: 6.2 - 7.5,
Distribution:  Africa: basins of upper and middle Niger River, BenouĂ© and upper Volta in Guinea, Mali, Burkina Faso, Ghana, Benin, Cameroon (Ref. 57474), Chad (Ref. 367) and Ivory Coast (Ref. 3066). Probably also in Togo, Nigeria and Niger (Ref. 57474).
Diagnosis:  Dorsal soft rays (total): 9-10; Anal soft rays: 7-8; Vertebrae: 40-43. Diagnosis: pelvic fin origin at level of anterior base of dorsal fin; preorbital stripe present; caudal peduncle depth 6.9-11% of SL; dorsal precaudal fin fold not reaching base of dorsal fin; 8-9 pectoral fin rays; 7 pelvic fin rays; 2 supernumerary rays in anal fin; 8 dorsal fin pterygiophores; 9+9 principal caudal fin rays; cephalic lateral line canals and supraorbital bone present; parasphenoid wide, with foramina for internal carotid arteries; neural spine of 2nd vertebra short and wide, only the length of its vertebral centrum and different from subsequent neural spines (Ref. 57474). Description: body elongate, slightly laterally compressed, caudal peduncle depth nearly identical to body depth; body scaleless; snout rounded; mouth inferior and in front of eyes, protractile, mouth opening very small; lips unculiferous; jaws toothless; opercular opening reduced to a tiny semilunate opening above pectoral fin base (Ref. 57474). Gill rakers long, slender, closely spaced and numerous, up to 90 on first gill arch; elongate finger-shaped epibranchial organ with a central lumen between 4th and 5th gill arch; intestine about 1.5 times SL (Ref. 91276). Precaudal fin fold present, not extending up to dorsal fin base; 7 pelvic fin rays plus pelvic splint; 9-10 dorsal fin rays, including 2 (rarely 1) supernumerary rays; 8 dorsal fin pterygiophores; 7-8 anal fin rays, including 2 (rarely 1) supernumerary rays; 6 anal fin pterygiophores; caudal fin forked with 7-11 dorsal procurrent rays, 9 upper and 9 lower principal rays and 6-9 procurrent ventral rays; 40-43 vertebrae, 27-29 abdominal and 12-15 caudal; ribs on all abdominal vertebrae except first 2; 3 branchiostegal rays (Ref. 57474). For more details on osteology see Ref. 57474 and Ref. 89095 (skull, axial skeleton, suspensorium) and d'Aubenton 1961 (detailed skull morphology). Coloration: in life: translucent, peritoneum greenish with silvery reflection; dark preorbital stripe on side of snout in front of eye, continued as a stripe in opercular region and about 10 bold rectangular mid-lateral blotches along sides of body with 1 blotch (sometimes divided into 2) at middle of base of caudal fin; slightly above mid-lateral row of blotches a thinner row of about 16 black stipple-like marks approaching mid-lateral row on caudal peduncle, but ending before base of caudal fin slightly in front of last mid-lateral body blotch; a series of dark mid-dorsal blotches starting at anterior head region with the one at base of dorsal fin often enlarged and more conspicuous than others and most posterior ones extending along dorsal edge of caudal fin; often with numerous irregular small spots between mid-dorsal series of blotches and lateral series of small stipple-like marks; 2 series of dark spots on interradial membranes of caudal fin forming 2 narrow vertical lines; a mid-ventral row of small black spots along caudal peduncle; a black smudge at base of anal fin; dorsal fin with a narrow stripe at distal third; pelvic, pectoral and anal fins transparent; intensity of coloration in life depends heavily on brightness of substrate and can be adapted within a few hours; anaesthetized live individuals lose most of the color pattern within minutes (Ref. 57474). Preserved specimens not translucent, depending on preservative yellowish brown or pale white; myosepta clearly visible; preorbital black stripe , mid-dorsal series of blotches and color marks on caudal fin, caudal peduncle and base of anal fin persist; some individuals with patches on opercular region or single dots on dorsal flanks (Ref. 57474).
Biology:  Maximum TL was recorded at 4.1 cm (Ref. 3566). Occurs on several substrates from fine mud to rough gravel and plant material; almost never buries into the substrate (Ref. 57474). Feeds on plankton (Ref. 57474, 91322) and phytoplankton (Ref. 91322). Reproduction likely takes place during the rainy season (August to September) (Ref. 57474) at high water levels in floodplains, brooks or rice fields (Ref. 91276, 91322).
IUCN Red List Status: Least Concern (LC); Date assessed: 15 May 2019 Ref. (123251)
Threat to humans:  harmless
Country info:   
 

Entered by: Sa-a, Pascualita - 18.06.94
Modified by: Musschoot, Tobias - 21.09.15

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