Cromeria nilotica Boulenger, 1901
Naked shellear
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Family:  Kneriidae (Shellears), subfamily: Kneriinae
Max. size:  2.9 cm SL (male/unsexed)
Environment:  benthopelagic; freshwater,
Distribution:  Africa: Upper White Nile basin in Sudan (Ref. 57474) and Ethiopia (Ref. 58460).
Diagnosis:  Dorsal soft rays (total): 9-10; Anal soft rays: 9-10; Vertebrae: 41-45. Diagnosis: pelvic fin origin well in front of anterior base of dorsal fin; preorbital stripe absent; caudal peduncle depth 10.1-12.9% of SL; dorsal precaudal fin fold more pronounced, reaching base of dorsal fin; 6-7 pectoral fin rays; 6 (rarely 7) pelvic fin rays; 3 (rarely 2) supernumerary rays in anal fin; 7 dorsal fin pterygiophores; 8+8 principal caudal fin rays; cephalic lateral line canals and supraorbital bone absent; parasphenoid slender, without foramina for internal carotid arteries; neural spine of 2nd vertebra long and slender, at least 2 times length of its vertebral centrum and similar in shape to subsequent neural spines (Ref. 57474). Description: body elongate, strongly laterally compressed, caudal peduncle depth nearly identical to body depth; scaleless; snout rounded; mouth inferior and in front of eyes, protractile, opening very small; lips unculiferous; jaws toothless; opercular opening reduced to a tiny semilunate orifice above pectoral fin base; deep precaudal fin fold extending anteriorly up to dorsal and anal fin bases; pelvic fin rays 6(-7) plus pelvic splint; 9-10 dorsal fin rays, including 2-3 supernumerary rays; 7 dorsal fin pterygiophores; 8-10 anal fin rays, including (2-)3 supernumerary rays; 6 (rarely 7) anal fin pterygiophores; caudal fin forked with 7-13 dorsal procurrent rays, 8 upper and 8 lower principal rays and 8-12 procurrent ventral rays; 41-45 vertebrae, 27-29 abdominal and 13-16 caudal; ribs on all abdominal vertebrae except first 2; 3 branchiostegal rays (Ref. 57474). Cranium with many pecularities, mainly due to the enormous size of the brain (Ref. 31439). Details on osteology in Moritz et al 2006 (Ref. 57474) and Swinnerton 1903; detailed skull morphology in Boulenger 1907 (Ref. 31439) and Gregory 1933. Coloration: in alcohol: overall light brown background color caused by preservation of musculature with myosepta clearly visible; no marks on flanks except a narrow horizontal stripe along horizontal septum extending from level of posterior dorsal fin base to caudal peduncle; numerous small spots along dorsum, densest on dorsal precaudal fin fold; smaller chromatophores surrounding base of caudal fin; scattered chromatophores on dorsal part of head, and lining fin rays of dorsal fin, present also at base of anal fin and at upper and lower most parts of caudal fin; occasionally with individual spots on opercular region; rarely with well marked black stripe along entire horizontal septum and with dorsal flanks densely covered with brown spots, individual spots also below midline, dark spots on pelvic, dorsal and base of anal fin, and a few chromatophores on ventral midline between anal and pelvic fins (Ref. 57474). Live coloration unknown, but probably colorless translucent with the above mentioned dark marks (Ref. 57474).
Biology: 
IUCN Red List Status: Least Concern (LC); Date assessed: 01 May 2009 Ref. (123251)
Threat to humans:  harmless
Country info:   
 

Entered by: Cruz, Tess - 17.03.92
Modified by: Musschoot, Tobias - 14.08.12
Checked by: Sa-a, Pascualita - 18.06.94

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