Diagnosis: jaws greatly enlarged in mature males; scales in 2-3 rows on cheek; caudal peduncle relatively shorter than in O. mossambicus (Ref. 2). In life greenish grey (Ref. 2), green-blue (Ref. 52307) or grey-blue with a darker spot on each scale (Ref. 2, 52307). Females and immature males often with 1-3 dark mid-lateral blotches (Ref. 2, 52307), which may appear only as the fish dies (Ref. 2). Breeding males: predominantly iridescent blue-green to bronze (Ref. 2, 52307), with iridescent spots on dorsal and caudal fins (Ref. 2), a dorsal fin with a red edge that is not as pronounced as in O. mossambicus, and a narrow (as opposed to wide) red band at posterior end of caudal fin (Ref. 12524, 13337).
Description: moderately deep-bodied; duckbill-shaped snout and large mouth, mostly seen in large males (Ref. 52307). Upper profile of snout concave in large breeding males; maxillary ending between nostril and eye; teeth in 3-5 series, mostly outer bicuspid, inner tricuspid; lower pharyngeal bone narrow with sides of dentigerous area concave; pharyngeal teeth fine (Ref. 2). Gill-rakers dense, slender and long (Ref. 3126). 4-6 scales between bases of pectoral and pelvic fins (Ref. 2). Caudal peduncle shorter than (Ref. 2, 52307) and coloration slightly different from O. mossambicus (Ref. 52307). Caudal fin occasionally with lower or both corners rounded; caudal fin not heavily scaled (Ref. 2).
Coloration: body dark green with occasional black specimens (Ref. 12524, 13337). Body usually white on ventral surface (Ref. 2). Lower parts of cheeks and opercles bluish (Ref. 2, 52307). 2-5 dark but rather obscure mid-lateral blotches or bands may appear (Ref. 54048, 54096), especially as the fish is dying or preserved (Ref. 54096). Dorsal and caudal fins possess red to orange margins that are normally broader and more intense in males (Ref. 2, 52307, 54048, 54096). Numerous green iridescent dots usually visible in dorsal fin (Ref. 2, 52307). Sometimes a group of shining white spots on posterior rays of dorsal and anal fin (Ref. 2, 54096). Caudal fin usually with a grey reticulum (Ref. 2, 54096) on proximal 2/3 with pale or iridescent interstices (Ref. 2). Courting males appear bright blue-green to bronze, with dorsal areas usually darkest and most intense in color; throat exhibits same coloration as body (Ref. 52307), dark grey (Ref. 54048), dark green or black (Ref. 2, 12524, 13337, 54048). Breeding male may have a red flush on the operculum and on the flanks in the vicinity of the pectoral fin (Ref. 54096); the dark opercular spot may have a metalic gold patch above and below it; the breeding female may also develop iridescence, bronzy on the flanks and bluish on the fins (Ref. 54096). Eyes yellowish; golden specimen known (Ref. 54048).