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Dorsal spines (total): 15-17; Dorsal soft rays (total): 11-14; Anal spines: 3-3; Anal soft rays: 9-12; Vertebrae: 29-32. Diagnosis: head profile steep (Ref. 2, 7248, 12524, 13337, 33478, 52193, 54167) and rounded (Ref. 315, 12524). Toothed area of lower pharyngeal bone with broadly rounded lobes; scales on cheek in 2-3 rows; caudal scales variable, not on the inter-radial membranes except at the base, and never stiffening the fin (Ref. 2). Adults with black (Ref. 2, 12524) or dark brown flecks in the temporal region, on the gill-cover (Ref. 2, 11970) and below the eye, mostly associated with openings of the lateral line system (Ref. 2). Adults without conspicuous mid-lateral blotches (Ref. 2).
Description: body deep (Ref. 52307), fairly compressed (Ref. 56454), with deep caudal peduncle (Ref. 2, 52307). Snout short (Ref. 2, 52307), rounded, sometimes with concave upper profile, a little broader than long, shorter than postocular part of head (Ref. 1887, 54167). Head develops a steep profile (Ref. 2, 1887, 7248, 12524, 13337, 33478, 52193) with increasing size, especially in males (Ref. 33478). Mouth rather small (Ref. 1887, 54167), reaching to just behind level of anterior nostril (Ref. 56454). Outer row teeth in jaw enlarged, slender, most bicuspid, inner teeth minute, tricuspid (Ref. 56454). 2-3 rows of scales on cheek (Ref 1887, 46242, 54167, 56454), width of scaly part not greater than eye diameter (Ref. 1887, 54167). Nape scaled to level of front third of eye; eye round, its diameter almost equals interorbital width in juveniles, a little over half interorbital width in adults; pharyngeal teeth closely packed, slender (Ref. 56454). Otoliths: regular oval outline and moderately developed, rather regular ornamentation; sagittae of juveniles have an S-shaped sulcus with a distinct upward bend near the end of the cauda, often accompanied by a more or less distinct widening of this part of the cauda; sagittae ornamentation consists of more or less regular, rounded knobs (Ref. 56279). Gill-rakers short (Ref. 46242, 54167), lanceolate (Ref. 46242), thick (Ref. 54167). Vertebrae 16+14, including urostyle (Ref. 56454). Scales cycloid (Ref. 1887, 54167, 56454). 18-23 scales in upper part of lateral line (Ref. 1887, 46242, 56454), 11-14 in lower part (Ref. 1887, 11970, 56454). 12 transverse scales; 10-12 predorsal scales (Ref. 46242, 56454). Last dorsal fin spine longest (Ref. 1887, 54167, 56454). Third anal fin spine about equal to last dorsal fin spine (Ref. 56454). Pectoral fins very long (Ref. 2, 7248, 52193), reaching a vertical above some part of the anal fin base (Ref. 2, 56454), a little shorter than head (Ref. 54167). Pelvic fin shorter than pectoral fin, not quite reaching vent; caudal fin covered with small scales becoming sparser distally (Ref. 56454). Caudal peduncle as long as deep or a little deeper than long (Ref. 54167). Genital papilla large and tuberculate or scalloped in mature fishes of both sexes (Ref. 2). Bifid genital papilla without tassels in females, but in males with numerous (Ref. 33478), 2cm or longer (Ref. 2, 33478) semitransparent fringes with a knotted aspect generated by several tuberculate blobs (Ref. 33478).
Coloration: females and non-breeding males: body greenish, silvery or buff, with white or sometimes yellowish belly; snout, upper lip and cheeks with (blue-)green sheen; gill-covers and flanks sometimes with purplish tint; gill-cover with slight marblings and dark green or iridescent spot; forehead with a few dark specks in connection with lateral line openings; eyes with reddish tint; fins light grey, commonly with transparent or dusky end to caudal fin; tilapia-mark may be visible even in adults; some, mainly small, specimens may exhibit up to 7-8 transverse rows of spots on the caudal fin; in some, mainly stressful, situations, 7-9(10) dark vertical bars, including incomplete bars, may appear on the flanks, posteriorly from the eyes; even 1-2 horizontal stripes may appear; sexually active females show some of the male colours but to a lesser degree (a narrower red margin to the dorsal fin, without white underlining; caudal fin ends in dusky zone which may have a red hue); when spawning or mouthbrooding, females often darken partially on the lower jaw, fins, eyebar, tilapia-mark or on indistinct blotches on the flanks; a barred pattern, which includes forehead stripes, can be assumed by defensive brooding females (Ref. 33478). Breeding males: body and median fins dark grey to black with greenish or bluish hue (Ref. 2, 33478). Ventral surface can be lighter; a lighter zone runs from the snout over the top of the head and nape to the anterior part of the dorsum; on the head this light blue or green, even whitish area is dotted with numerous dark spots which may merge to a reticulum; scales on dorsum with dark centers, which extend the speckled pattern (Ref. 33478). Margins of dorsal and caudal fins red (Ref. 2, 4967, 33478, 56454) underlined posteriorly with white, or dusky in small males (Ref. 33478). Tassel-like genital papilla white (Ref. 2, 7248, 52193). Juveniles: silvery, with 6-10 thin straight vertical bars on body (Ref. 1887, 7248, 12524, 13337, 52193). Orange/yellowish fins (Ref. 7248, 12524, 13337, 52193). Caudal fin irregularly spotted centrally (Ref. 2). Preserved specimens: dark brown above, lighter below; base of scales dark, forming indistinct longitudinal streaks between the series; 8-10 dark cross-bars on body, and a faint longitudinal streak from opercle to base of caudal; dark opercular spot; vertical fins with faint dark and light spots forming oblique streaks; tip of dorsal fin and distal extremity of anal fin whitish; a dark spot at base of anterior rays of soft dorsal; snout dark (Ref. 54167). |
| Prefers quiet, deep water associated with aquatic vegetation, but has been collected in other habitats as well (Ref. 12524, 13337). Found at temperatures between 18 and 35°C (Ref. 54042). Has a very low salinity tolerance (Ref. 2, 58). Occasionally forms schools, is mainly diurnal (Ref. 2). Feeds mostly on detritus (Ref. 87, 7248, 44661, 52193, 52307, 56192), (blue-green) algae (Ref. 12524, 13337, 44661) and diatoms (Ref. 246, 7248, 12524, 13337, 52193). Juvenile also accepts small invertebrates and zooplankton (Ref. 7248, 52193, 52307), but lose this tendency with age (Ref. 52307). Maternal mouthbrooder (Ref. 87, 246, 314, 5214, 7248, 8600, 12524, 13337, 36094, 52193, 54042). Mating territory having a central volcano-shaped mound (Ref. 2, 246, 314, 5214, 12524, 55074) with a flat or slightly concave top, surrounded by a ditch and vallum, in contrast to O. mweruensis (Ref. 2). Flesh excellent (Ref. 5214). |
