Diagnosis: Haplochromis sphex is a small sized (less than 9 cm standard length), slender (body depth less than 32% of standard length) micrognathic species, with mainly bicuspid teeth in the oral jaws; dorsal head profile straight to moderately curved (Ref. 85523). The colouration of the sexually active males is yellow with blackish longitudinal, interrupted bands and vertical bars, producing a so-called 'chess board pattern'; this pattern also occurs in several oral shelling molluscivores, insectivores and algae scrapers, but these species generally are larger, have a deeper body, have a strongly curved dorsal head profile and a lower jaw length/width ratio of less than 1.5, whereas in Haplochromis sphex it ranges from 1.5 to 2.7 (Ref. 85523). It differs from other small species with a 'chess board pattern', H. bwathondii and H. sauvagei, by its shallower body; sexually active males of H. sauvagei generally have a more distinct 'chess board pattern' than H. sphex; in contrast to H. sphex, sexually active males of both H. bwathondii and H. sauvagei develop a red chest and belly; the colouration of females and quiescent males of H. sauvagei is rather similar to that of sexually active males of H. sphex (Ref. 85523).
Description: Body slender; dorsal head profile straight to moderately curved; premaxillary pedicel not prominent (Ref. 85523). Mouth slightly oblique; lips normal; medial part of the premaxilla not expanded; caudal part of the maxilla not bullate; the vertical through the caudal tip of the maxilla runs through the iris; lateral snout outline isognathous to slightly prognathous and obtuse; jaws equal anteriorly or lower jaw slightly protruding; mental prominence not pronounced; retro-articular processes of right and left mandibles generally just not touching each other, slightly interrupting the ventral outline; eye approximately circular; a small aphakic aperture may be present; cephalic lateral line pores generally not enlarged (Ref. 85523). Cheek, gill cover, dorsal head surface, greater part of dorsum and caudal fin base covered with cycloid scales, the remaining part of the body with ctenoid scales; a gradual size transition between scales of chest and flank; four to six scales between the upper lateral line and the dorsal fin origin, five to seven between the pectoral and the pelvic fin bases (Ref. 85523). Pelvic fins just reaching the anal fin origin; first soft rays of pelvic fins slightly produced, occasionally filamentous; anal fin just not reaching caudal fin origin; caudal fin outline truncate to slightly emarginate (Ref. 85523). The number of gill rakers on the lower part of the first gill arch is 12 to 13; the lower two to three rakers are reduced; next one to three rakers are short; these are followed by two to four long, acutely pointed rakers; the remaining rakers are long, their shape is acutely pointed to bifid or quadrifid; the rakers on the first gill arch are touching each other; the number of gill filaments on the lateral hemibranch of the first gill arch ranges from 97 to 100 (Ref. 85523). Premaxillary dentigerous arm slightly shorter than, or as long as ascending arm; the angle between the two arms is 83° to 84°; symphyseal articulation facet not present; lower jaw slightly elongated; the upper half of the dentary has an outwardly directed flaer, which is slightly to moderately distinct; mental prominence not pronounced; teeth in the rostral part, ca. 2/3 of dentigerous area, of both premaxilla and lower jaw generally unequally bicuspid, often with a few tricuspids among them; in the caudal part of the premaxilla, tricuspids, weakly bicuspids and unicuspids can be found; in males the caudal-most teeth are slightly enlarged to enlarged weakly bicuspids or unicuspids, in females the caudal-most teeth are not enlarged and tricuspid; the teeth in the caudal part of the lower jaw may be either tricuspid, weakly bicuspid or bluntly unicuspid; the shape of the major cusp in bicuspid teeth is isoscelene to subequilateral; a very small to small flange is present on rostrally positioned teeth; in caudally positioned teeth the flange can be absent; the tip of the major cusp is elevated above the flange; the cusp gap is wide to moderately wide, the minor cusp is small but distinct; in labial view, the neck is stout, the crown not expanded to slightly expanded; in lateral view, the crown is slightly compressed; premaxillary outer row teeth slightly to strongly recurved, lower jaw outer row teeth slightly recurved; the inner row teeth of both premaxilla and lower jaw are tricuspid; teeth are relatively small and slender (Ref. 85523). Dental arcade rounded and U-shaped; premaxilla two to three or four inner rows anteriorly, none posteriorly; lower jaw, one to three inner rows anteriorly, none posteriorly; there are 42 to 56 teeth in the outer row of the upper jaw; the outer row teeth in both premaxilla and lower jaw are normal to closely set, caudal-most positioned teeth may be somewhat more widely set; outer row teeth of premaxilla erect, inner row teeth recumbent; lower jaw outer row teeth erect to slightly procumbent, inner row teeth erect (Ref. 85523). Lower pharyngeal element relatively slender, as broad as it is long or slightly longer than broad; the dentigerous area is broader than long; the suture is straight; there are 31 to 34 pharyngeal teeth in the caudal-most transverse row, 9 to 11 teeth in the medial rows; caudal-most one to two transverse rows hooked, major cusp only slightly incurved and blunt; other teeth pronounced or bevelled; all teeth relatively fine and slender, medial teeth not coarser than other teeth (Ref. 85523). The total number of vertebrae is 29-31, comprising 13-14 abdominal and 15-17 caudal vertebrae (Ref. 85523).
Colouration: Live colouration of males: snout and dorsal head surface yellow; eye with a dusky outer ring and a yellow inner ring; lips yellow to sooty; lower jaw yellow to ivory; interoperculum and gill cover yellow; cheek, chest, dorsum, flank and belly yellow, with sometimes a silverish ground colour shining through; ventral side yellow to ivory, sometimes a bit sooty; nostril-, interorbital-, lachrymal-, supraorbital-, preopercular vertical stripes and nape band present; there are four to six, rarely seven vertical bars on the flank; a interrupted mid-lateral- and dorsal lateral band are present, as well as traces of a dorsal medial band; the mid-lateral band is anteriorly extended until the eye and posteriorly over the entire caudal fin; the markings are dusky to black; in cases where vertical bars are present and the horizontal bands are uninterrupted a so-called 'chess board pattern' emerges; pectoral fins hyaline with a sometimes brown-red or dusky base, pelvic fins laterally black, medially yellowish-hyaline; the anal fin is hyaline-grey, caudally becoming more hyaline, generally with three yellow to yolk-yellow egg dummies surrounded by a hyaline ring; caudal fin hyaline with faint brown-reddish streaks and spots, a dusky base and the extension of the mid-lateral band; dorsal fin sooty-yellow, caudally becoming hyaline, with faint red-brown streaks and spots; dorsal fin base partly black, lappets dusky (Ref. 85523). Live colouration of females: coloured like males but the yellow parts generally are olive-green, though a faint yellow flush is present at the ventral side of the flank; in the centre of the flank, some traces of blue may be present; chest, belly and ventral side silverish; branchiostegal membrane yellowish; faint traces of lachrymal-, supraorbital- and preopercular vertical stripes and nape band may be present; there are four to six vertical bars on the flank, which are less distinct than in males; black opercular blotch present, as are an interrupted mid-lateral-, dorsal lateral- and dorsal medial band; mid-lateral band extending to one third of the caudal fin; pectoral fins hyaline, pelvic fins yellow; anal fin hyaline-yellow with yolk-yellow spots; dorsal and caudal fin hyaline-grey with brownish streaks and spots (Ref. 85523). Preserved colouration of males: entire body grey-brown to yellow-brown, generally ventrally lighter than dorsally; markings as in live, sexually active males; pectoral fins brownish-hyaline; pelvic fins laterally black, medially brownish-hyaline to dusky; dorsal fin brownish-hyaline, occasionally with darker streaks and spots, lappets sometimes dusky (Ref. 85523). Preserved colouration of females: females are coloured like males, except for the nostril-, interorbital-, lachrymal-, supraorbital- and preopercular vertical stripes, which are absent (Ref. 85523).