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Dorsal spines (total): 15-18; Dorsal soft rays (total): 10-13; Anal spines: 3-4; Anal soft rays: 9-11; Vertebrae: 27-29. Diagnosis: A small medium-sized tilapia, with a relatively deep, flattened body and small head and jaws (Ref. 118638). Lower jaw not longer than 34% of the head, preorbital depth not more than 23.2%; teeth of jaws and pharynx very small, those of the lower pharyngeal restricted to the posterior part of the pad; 27-29 vertebrae (Ref. 2). Scales on lateral line 28-30 (Ref. 2, 34290, 54836), rarely 31 or 32 (Ref. 2). Gill-rakers on lower part of first gill-arch 19-24 (Ref. 34290, 54836). Length/depth ratio of caudal peduncle 0.5-0.8 (Ref. 34290). Males are black with white spots on the flanks and fins; females are more olive coloured, with pale ventral regions, faint vertical barring and dark anal and tail fins (Ref. 2, 4903, 34290, 118638). Lower lip often bluish-white; 8 to 12 dark vertical stripes sometimes visible on flanks (Ref. 2, 4903, 34290). Dorsal, anal and caudal fins dark; soft dorsal, entire caudal and anal fins with well-defined bluish-white spots (Ref. 4903, 34290). Genital papilla intensely white in both sexes (Ref. 2). Ground color in breeding males changes to dark blue-black, whilst whitish spots on body and fins are intensified; eye outstanding with its bright amber iris crossed by a black bar (Ref. 2, 4903, 34290).
Description: body moderately deep in very young fish, becoming slender and lozenge shaped with increase in length (Ref. 55020). Maxillary ending below nostril (Ref. 55985) or a little behind it, between nostril and eye (Ref. 55074, 55985). Teeth very small, in 3-6 series, outermost bicuspid, inner tricuspid (Ref. 2, 55985). 2 series of scales on cheek (Ref. 2, 55985), rarely 1 or 2 scales of a third series (Ref. 2). Lower pharyngeal bone slender, its width usually less than, occasionally equal to, its median length (Ref. 2). Pharyngeal teeth very fine and crowded (Ref. 2), restricted to the posterior part of the pad in adults (Ref. 2, 55985). Flanges on either side of the apex of the triangular area of the lower pharyngeal bone unusually broad; microbranchiospines on outer surfaces of second, third and fourth arches; 7 scales over top of caudal peduncle above lateral line (Ref. 2). Generally 4, rarely 3, scales along the lateral series in the length of the caudal peducle (Ref. 56137). Genital papilla small, but white (Ref. 2, 56136) and conspicuous throughout life, crenellated in mature fishes of both sexes (Ref. 2). Dorsal fin reaching caudal fin base in juveniles and middle of caudal fin in adults; anal fin reaching as far backwards as dorsal fin; pectoral fins reaching anal fin base; pelvic fins reaching vent (Ref. 55074). 3-5 scales between bases of pectoral and pelvic fins; last anal fin spine about as long as last dorsal fin spine (Ref. 55985).
Coloration: adults generally dark olive-green with white spots (Ref. 2, 4967, 56137) on the flanks formed by the paler centre of each scale (Ref. 2, 54836, 55074, 56136, 56137). If a pattern is present on the caudal fin, it consists of bluish white spots in a dark reticulum, but this may be restricted to the base or middle of the fin or masked by melanin; iridescence of opercular blotch and preorbital bone produces a dark violet effect (Ref. 2). Lower lip white (Ref. 56136). Dorsal fin usually without red marginal band (Ref. 2, 54836). Dorsal, soft anal and caudal fin spotted (Ref. 55985). Breeding males with a very dark blackish (Ref. 2, 55074, 56137) to blue-green body (Ref. 2, 56137) covered with intense white spots above the anal fin (Ref. 2), and a bright yellow iris that is crossed by an oblique dark bar in life (Ref. 2, 55074, 56136, 56137). Dorsal fin in breeding males may have some red color (but not opaque bright red as in other species) mixed with melanin, which disappears as the fish dies, leaving the lappets black (Ref. 2). Lower lip may be bluish green or greenish white in living male (Ref. 2, 56137), but becomes dark in preserved fish (Ref. 2). Branchiostegal membrane may have yellow patches in non-breeding fish and females, but is black in brooding females (Ref. 2, 56137). Juveniles: body usually dark blue (Ref. 55020) or greenish grey (Ref. 55020, 55074, 56136), with lighter ventral surface and scales showing up distinctly (Ref. 56137). 8-12 dark vertical bars on body (Ref. 2, 55074, 56137), extending from dorsal fin to belly (Ref. 56136). Bars may fade quickly in dead fish; one horizontal stripe is often prominent and appears to be caused by the localized intensification of the pigment of the vertical bars; iris usually with orange spot, intensifying with age (Ref. 55020). Indistinct Tilapia-mark (Ref. 2, 4903, 56136) marbling on a yellowish background (Ref. 2, 4903, 56137), taking the form of a dark bar reaching the depth of the dorsal fin and edged by a translucent area (Ref. 55020), but no longer distinguishable at 6.5-7.0cm SL (Ref. 2, 55020). Soft part of dorsal fin (Ref. 55020, 56136), and caudal and anal fins spotted with light circular spots which appear first at about 2.5cm and intensify with age (Ref. 55020). |
| Occupies an inshore zone and is common in lagoons (Ref. 87). Occasionally forms schools (Ref. 2, 39939). Is mainly diurnal (Ref. 2). Can tolerate considerable deoxygenation (Ref. 2, 1739, 4903, 13046, 32297) and warm temperatures (Ref. 2060), known to occur at 38.0 °C (Ref. 2). Feeds on phytoplankton (Ref. 2, 21, 4903, 34291, 55486) and detritus (Ref. 34291, 55486, 56058). Ovophilic (Ref. 2060), a maternal mouthbrooder (Ref. 4903, 34291, 55074, 118638). Males dig simple pits in shallow water (Ref. 118638). Strongly prone to precocious maturity; this makes it an undesirable aquaculture species (Ref. 118638). Caught in large numbers by small-meshed nets in shallow swampy areas, where it has become established (Ref. 118638). When stocked along with Nile tilapia, probably will assist in filling all suitable niches and competitively excluding native species (Ref. 118638). |
