Diagnosis: Females and non-breeding males of Melanochromis mpoto are distinguished from all congeners, except M. melanopterus, M. vermivorus, and M. baliodigma, by a dark brown body and a melanin pattern, when discernible, consisting of two dark horizontal stripes combined with dark vertical bars; the only other Melanochromis species with such a pattern is M. baliodigma, but M. mpoto differs from the latter species by having vertical bars that are narrower than either horizontal stripe; in M. baliodigma the vertical bars are much wider than the horizontal stripes; mouthbrooding females of M. robustus can exhibit vertical bars as well, but this species has a greater interorbital width compared to that of M. mpoto, 26.1-29.6% of head length vs. 14.8-21.8% in M. mpoto (Ref. 89864). Melanochromis mpoto differs from M. melanopterus and M. vermivorus by a shallower cheek depth, 15.4-21.7% of head length vs. 22.9-31.7% of head length in M. melanopterus and 28.2-36.2% of head length in M. vermivorus (Ref. 89864). Male M. mpoto in breeding colouration are light blue/blue without any bars or stripes visible on the flank; and Melanochromis mpoto males are thus distinguished from those of most other Melanochromis species except M. lepidiadaptes, M. kaskazini, and M. wochepa; Melanochromis mpoto differs from M. wochepa males and females by its longer lower jaw, 38.1-42.4% of head length vs. 26.7-32.5% in M. wochepa); it differs from M. lepidiadaptes males by the black submarginal band in its anal fin, which is entirely light blue in fully coloured males of M. lepidiadaptes; in partially coloured males of the latter species the black horizontal stripes are visible, but no vertical bars are present, as is the case in M. mpoto (Ref. 89864). Males of M. mpoto differ from those of M. kaskazini by possessing more teeth in the lower jaw, 18-23 vs. 10-16 in M. kaskazini; by having a shallower preorbital depth, 15.4-20.4% of head length vs. 19.3-26.9% in M. kaskazini; and by possessing a shallower cheek, 15.4-21.7% of head length vs. 19.8-28.0% in M. kaskazini; fully coloured males of M. mpoto and M. kaskazini are indistinguishable on the basis of colouration alone, but the basic melanin patterns of the two species, as seen in juveniles and adult females, differ dramatically (Ref. 89864).
Description: Medium-sized mbuna, spindle-shaped body with greatest depth at about 9th to 11th dorsal spine; dorsal body profile with gradual curve towards caudal peduncle; ventral body profile straight to slightly convex in females and convex in adult males between pelvic fins and base of rays of anal fin; posteriorly, ventral body profile gradually curving dorsally toward caudal peduncle; dorsal head profile slightly rounded, with continuous convex curve between interorbital and dorsal-fin origin (Ref. 89864). Horizontal eye-diameter considerably greater than cheek depth; approximately 3/4 of eye, along horizontal axis, located in anterior half of head; snout elongate and straight with isognathous jaws; tooth bands with 3-4 rows in lower and 3-5 rows in upper jaw, with noticeable gap between first and second row; teeth in anterior outer row equally to unequally bicuspid in females and unequally bicuspid to unicuspid in males; teeth in inner rows mostly unicuspid; single series of unicuspid teeth at junction of outer and innermost rows (Ref. 89864). Lower pharyngeal bone triangular with moderate posterior indentation; few median teeth slightly enlarged but with pointed tips; other pharyngeal teeth laterally compressed with blade-like, curved tips (Ref. 89864). Dorsal fin with XVII-XVIII spines and 9-10 soft rays; anal fin with III spines and 7-8 soft rays; first 4 or 5 dorsal spines becoming gradually longer posteriorly with fourth spine about twice length of first; last 12 spines becoming slightly longer posteriorly with last spine longest, about four times length of first; soft portion of dorsal fin with in females rounded tip and in males rounded to subacuminate tip, fourth or fifth ray longest, reaching base of caudal fin in females and to approximately 1/4 length of caudal fin in males; anal-fin spines becoming progressively longer posteriorly; fourth or fifth ray longest, reaching base of caudal fin; caudal fin subtruncate to emarginate; posterior tip of pelvic fin extending to approximately anal fin in females or to second or third spine of anal fin in large males; pectoral fin paddle-shaped, posterior tip extending to vertical line through base of 11th or 12th dorsal spine (Ref. 89864). Flank scales large, ctenoid, with abrupt transition to small scales on breast; cheek with 5-7 rows of small scales; 50-75% of caudal fin covered with tiny scales; no scales present on other fins (Ref. 89864).
Colouration: Breeding males with head and body cyan blue; dorsal fin cyan blue with pale-blue distal margin and white lappets; caudal fin cyan blue with pale-blue submarginal band and narrow yellow distal margin; anal fin gray/blue with light-blue distal margin and 3-5 small yellow ocelli; pelvic fin gray/blue with white/light-blue anterior margin; pectoral fin with light-gray rays and clear membranes; full male breeding colour conceals basic melanin pattern typical of females and juveniles (Ref. 89864). Females have head brown/dark brown with gray/brown gular region; body bluish-brown/dark brown, often with darker midlateral and dorso-lateral stripes and vertical bars; dorsal and caudal fins gray/brown with broad yellow posterior edge; anal fin gray/brown with 1-3 tiny yellow spots; pelvic fin brown with narrow white/light-blue anterior margin; pectoral fin with brown rays and gray/yellow membranes (Ref. 89864).