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Dorsal spines (total): 15-16; Dorsal soft rays (total): 8-10; Anal spines: 3-3; Anal soft rays: 8-10. Diagnosis: A relatively small species with a moderate body depth, laterally compressed, with generalised body shape, a terminal, slightly acute, symmetric mouth, lower jaw protruding, and relatively large eyes, 33.8% of head length vs. 23.7% in Haplochromis nubilus, 29.4% in H. akika, 30.5% in H. commutabilis (Ref. 85068). It shares with other East African fluviatile species, especially the so-called Astatotilapia, the smaller longitudinal scale count, less than 31, compared to lacustrine species, more than 30, with exceptions H. akika, H. ampullarostratus, H. nubilus, from which, except for H. ampullarostratus, it is distinguished by its lesser body depth, less yhan 35% of standard length vs. more than 35% (Ref. 85068). From H. ampullarostratus it differs in, for instance, greater head length, 34.7-37.5% of standard length vs. 32.5-33.5%, and shorter snout length, 21.5-28.7% of head length vs. 29.1-31.4% (Ref. 85068). Additionally it differs from H. nubilus in head shape, dorsal head profile straight vs. concave, and nuptial colouration, solid black in H. nubilus vs. colourful, and colour of anal fin which is plain red in nuptial-coloured males of H. katonga vs. only marginally reddish or different-coloured in all other fluviatile species (Ref. 85068). The overall nuptial colouration of males is also a diagnostic feature: live colouration of males bluish to dark grey-brown on dorsum, flanks greenish, ventral parts yellowish, with reddish areas in unpaired fins; of females greyish blue to greyish yellow with a faint metallic blue hue dorsally (Ref. 85068).
Description: Relatively small species with generalised body shape; body moderately deep, compressed laterally (Ref. 85068). Head moderately large with relatively large eye and small mouth; cheek depth comparatively small, eye depth greater than cheek depth; snout pointed, isognathous, lower jaw slightly protruding, upper and lower profiles equally angled; dorsal head profile almost straight, premaxillary pedicel not prominent; maxillary posterior extension reaching vertical line through iris; lips not thickened, maxilla not bullate; lower horizontal border of preoperculum convex, rounded, curvature extending upward to maxilla; upper vertical border extending downward to meet this curvature; eye almost circular, relatively large, but not reaching dorsal outline of head; pupil slightly drop-shaped, with perimeter tapering caudally (Ref. 85068). Caudal peduncle longer than deep (Ref. 85068). Pectoral insertion located on imaginary line running posteriorly downwards from base of dorsal fin to base of ventral at angle of about 10° from vertical; pectoral not extending to vertical line through origin of anal fin; ventrals extending to this line; in adult males tips of dorsal and anal fins extending past vertical line through base of caudal fin, but not in females, where tips hardly reach that line; caudal fin subtruncate (Ref. 85068). Operculum partially scaled; suboperculum fully covered with cycloid scales; interoperculum fully covered by one row of cycloid scales; cheeks fully scaled; postorbital squamation with two rows of different-sized scales; size of occipital scales not significantly smaller than dorsal scales; predorsal squamation pattern irregular; cycloid and weakly ctenoid scales on dorsum rostrally, more strongly ctenoid scales increasing caudally; flanks with strongly ctenoid scales; granulation of flank scales covering area reminiscent in shape of a Viking axe, with relatively slight broadening horizontally and vertically at focus, but with extent larger than 150° at caudal margin; only caudal part of focus, for short distance to absolute centre of scale, strongly covered with granulae, close to centre having shape of tubercles, partly conjoined, closer to margin with shape reminiscent of short peanut-shells, and then gradually becoming longer towards margin and finally intergrading into large, conical denticles, only weakly curved or hooked; remaining part of focus of flank scale either covered only weakly with slightly thickened tubercles along circular structure or covered completely with grains; radii simple, except for last radii all of primary type; tongues on upper and lower margins short or even extremely short, but well developed at middle axis; first interradial circuli concave or straight, but with convex ridges extending onto tongue; scales immediately behind pectoral origin cycloid, but becoming more strongly ctenoid posteriorly; scales on caudal peduncle strongle ctenoid; scales on chest laterally and ventrally strongly ctenoid; large interpelvic scale present; scales on belly weakly ctenoid, about 1/3 smaller than flank scales and imbricating; scales on anal-genital region of similar size to flank scales, weakly to strongly ctenoid; scales on caudal cycloid, arranged in single row between and along rays; two scale rows between upper and lower lateral line, rostrally and caudally; four scale rows between upper lateral line and base of dorsal; four scale rows between bases of pectoral and ventral fins; lateral line scales 15-20+7-10 (Ref. 85068). Oral teeth in both jaws in adult moderately stout, relatively straight, bicuspid with two well-developed cusps, a mix between sub-equilateral and protracted, partly with flange; anterior teeth larger than posterior ones, latter sometimes replaced by teeth of different form, e.g. protracted and sometimes more slender; as in many Haplochromis species, posteriormost tooth in upper jaw unicuspid; teeth of inner rows smaller and tricuspid (Ref. 85068). Dental arcade rounded; only one row of inner teeth in lower jaw and two rows in upper jaw; wide gap between outer teeth and inner rows; teeth of inner lower jaw row extending further back than teeth of outer row, hence posteriormost lower jaw teeth tricuspid (Ref. 85068). Twenty teeth in lower jaw and 30-43 in upper outer row; teeth regularly positioned at small intervals anteriorly, posteriorly intervals larger or smaller, sometimes with aggregations visible; in smaller specimens teeth set more closely together; in both jaws teeth erect, slightly movable (Ref. 85068). Teeth on lower pharyngeal element bevelled; most teeth slender, only small number in centre of posterior part of dentigerous area enlarged (Ref. 85068).
Colouration: Live colouration of nuptial males: head and dorsum dark brownish, but with bluish grey elements on snout, occipital and anterior dorsal body, additionally with light blue metallic reflective highlights on some scales; laterally and on caudal peduncle greenish to olive with light green metallic reflective margins to scales; ventrally yellowish; greyish white on chest laterally, creamy white immediately behind gill opening; operculum mixed greenish yellowish, with large black opercular blotch; mere impression of oblique grey lacrymal stripe through iris and pupil, only faintly visible on cheeks; iris with yellowish pigmentation in rostral and caudal parts; dorsal fin brownish grey, anteriorly bluish grey, soft part with narrow red margin; caudal fin predominantly red, upper base to centre darkly olive; anal fin almost completely red, with two medium-sized egg spots; ventral fins dense black; pectorals hyaline with grey rays (Ref. 85068). Live colouration of quiescent males like that of females, with exception of ocelli in anal, which are larger and surrounded by hyaline ring (Ref. 85068). Live colouration of females: some females with entire body lightish brown to grey with some yellowish and greenish parts, others more bluish grey to grey; in both cases dorsal, caudal, and anal fins coloured as body, but slightly hyaline; ventrals hyaline with yellowish rays, pectorals yellowish hyaline with grey to yellow rays (Ref. 85068). Colouration in alcohol: males dark brown on flanks, with black-brown lateral stripe and five similarly coloured bars, two scales wide, extending dorsally only short distance above lateral stripe, and ventrally for only one additional scale; dorsally black-brown from tip of snout to base of dorsal fin; lachrymal stripe and preopercular vertical stripe visible; in females no lateral stripes or bars visible, but lachrymal stripe mostly present, otherwise flanks uniformly dark brown coloured; all the specimens of H. katonga exhibited an intense dark surface on some or most of their teeth, possibly an indication of their diet (Ref. 85068). |