Diagnosis: Orthochromis gecki can be readily distinguished from all species currently placed in Orthochromis, except O. torrenticola, which has eggspot-like maculae, by presence of eggspots on anal fin (Ref. 122085). It is further distinguished from O. kasuluensis by having fewer anal-fin rays, 8-9 vs. 10; from O. malagaraziensis by having more scales between upper lateral line and dorsal-fin origin, 5-8 vs. 3-4; from O. mazimeroensis by having more horizontal line scales, 29-31 vs. 26-28; from O. rubrolabialis, O. rugufuensis and O. uvinzae by having fewer anal-fin spines, 16-17 vs. 18-20, and in position of pterygiophore supporting last dorsal-fin spine, vertebral count 15-16 vs. 17-19; it is furthermore distinguished from O. uvinzae by having fewer abdominal vertebrae, 13-14 vs. 15-16, and by position of pterygiophore supporting last anal-fin spine, vertebral count 14-15 vs. 16-17 (Ref. 122085). Orthochromis gecki is distinguished from O. stormsi by having more horizontal line scales, 29-31 vs. 26-28, and fewer total gill rakers, 9-12 vs. 13-15; from O. polyacanthus by having fewer dorsal-fin spines, 16-17 vs. 18-20, more dorsal-fin rays, 10-12 vs. 8-9, and it is distinguished by position of pterygiophore supporting last dorsal-fin spine, vertebral count 15-16 vs. 17-18; from O. torrenticola by having fewer anal-fin spines, 3 vs. 4 (Ref. 122085). Meristic values of O. gecki overlap with those of O. luongoensis, O. kalungwishiensis, and O. machadoi but is distinguished by narrower interorbital width, 9.62-12.86% of head length vs. 13.18-21.27% (Ref. 122085). It is distinguished from Schwetzochromis neodon by having more circumpeduncular scales, 16 vs. 12; from Haplochromis snoeksi by having more anal-fin rays, 8-9 vs. 5-6; from Haplochromis bakongo by more horizontal line scales, 29-31 vs. 26-28, more dorsal-fin spines, 16-17 vs. 15, and by position of pterygiophore supporting last dorsal-fin spine, vertebral count 15-16 vs. 13-14; from Haplochromis moeruensis by having more horizontal line scales, 29-31 vs. 27-28, and more scales in upper lateral line, 21-25 vs. 19-20; meristic values of Orthochromis gecki overlap with those of Haplochromis vanheusdeni but is distinguished by having a smaller interorbital width, 9.62-12.86% of head length vs. 14.20-20.30% (Ref. 122085). It is distinguished from O. kimpala by having fewer series of scales on cheek, 0-2 vs. 3-4; meristic values of O. gecki overlap with those of O. mporokoso, O. katumbii, and O. indermauri but is distinguished by having smaller interorbital width, 9.6-12.9% of head length vs. 13.0-21.7% (Ref. 122085).

Description: Rather slender and elongated species with maximum body depth, 20.2-27.4% of standard length, slightly before or at level of first dorsal-fin spine, decreasing rather gradually towards caudal peduncle; caudal peduncle moderately elongated and deep, ratio of caudal peduncle length to depth 1.5-2.0 (Ref. 122085). Head length about one third of standard length; dorsal-head profile moderately curved, from anterior eye region to dorsal-fin origin only slightly curved; no prominent nuchal gibbosity present; eye diameter larger than interorbital width; jaws isognathous; posterior tip of maxilla almost reaching to slightly beyond anterior orbit margin; lips well developed (Ref. 122085). Anterior teeth of outer row of upper and lower jaw bicuspid to subequally bicuspid, large and closely set; towards corner of mouth, teeth smaller and more widely set and becoming unicuspid, rarely tricuspid or subequally bicuspid teeth present in posterior upper jaw; individual bicuspid teeth without or minimally expanded brownish crown, cusps, tips roundish, uncompressed and moderately narrowly set, neck moderately stout; outer row of upper jaw with 33-4 teeth and outer row of lower jaw with 26-42 teeth; larger specimens generally with more teeth; upper and lower jaw with 2-4 inner tooth rows with small tricuspid teeth, rarely 5 rows in upper jaw and 1 or 5 in lower jaw; larger specimens generally with more inner tooth rows (Ref. 122085). Lower pharyngeal bone about 1.1 times wider than long with anterior keel about 0.6 times length of dentigerous area; dentigerous area of lower pharyngeal bone about 1.4 times wider than long, with 10+9 teeth along posterior margin and 6 teeth along midline; anterior pharyngeal teeth, towards keel, beveled to pronounced and slender; those of posterior row larger than anterior ones, beveled, minor cusp not well developed; largest teeth medially in posterior tooth row; teeth along midline slightly larger than more lateral ones (Ref. 122085). Total gill raker count 9-12, with 1-2 epibrachial, one angle, and 7-9 ceratobranchial gill rakers; anteriormost ceratobranchial gill rakers smallest, increasing in size towards cartilaginous plug; anterior gill rakers on ceratobranchial unifid, towards cartilaginous plug sometimes bifid or trifid; raker on cartilaginous plug largest in size and in most cases trifid, sometimes bifid; epibranchial gill rakers then decreasing in size (Ref. 122085). Dorsal fin with 16-17 spines and with 10-12 rays; first dorsal-fin spine always shortest; dorsal-fin base length between 52.1-61.0% of standard length; posterior tip of dorsal-fin rays reaching slightly beyond caudal fin base; posterior tip of anal fin reaching slightly before or at caudal-fin base; caudal fin outline subtruncate and composed of 27-29 rays, 16 principal caudal-fin rays and 11-13 procurrent caudal-fin rays; anal fin with 3 spines, 3rd spine longest, and 8-9 rays; anal-fin base length between 15.6-20.7% of standard length; pectoral fin with 15-16 rays; pectoral-fin length between 19.6-25.0% of standard length; longest pectoral ray not reaching level of anus; first upper and lower pectoral-fin rays very short to short; pelvic fin with 1st spine thickly covered with skin and 5 rays; pelvic-fin base at level or slightly anterior of pectoral-fin base; pelvic fin ending at same level as pectoral fin; longest pelvic-fin ray not reaching anus, ending approximately 2-3 flank scale widths before (Ref. 122085). Two separate lateral lines; flank above and below lateral lines covered with comparatively large ctenoid scales; anterior dorsal and ventral flank covered by cycloid scales; margin of belly with deeply embedded minute to small sized scales; central belly region scaleless; chest completely scaleless, except for deeply embedded cycloid scales ventro-anteriorly of pectoral fin; chest to flank transition relatively abrupt with small, embedded cycloid scales; snout scaleless; interorbital region scaleless or with minute, deeply embedded cycloid scales; nape region covered with minute to small, embedded cycloid scales becoming slightly larger towards occipital region; occipital region with small to medium sized cycloid scales; cheek covered with small, partly deeply embedded cycloid scales sometimes almost appearing scaleless; 0-2 scale rows on cheek; cycloid scales on operculum of variable size, small to medium, and variable shape, ovoid to circular; opercular blotch only on anterior margin covered with medium sized scales, main area of opercular blotch scaleless; 1-3 scales in column from edge of postero-dorsal angle of operculum to anterior edge of operculum; upper lateral line scales 21-25 and lower lateral line scales 8-12; horizontal line scales 29-31; caudal fin with 0-1 pored scales; upper and lower lateral lines separated by two scales; 5-8 scales between upper lateral line and dorsal-fin origin; anterior part of caudal fin covered with 2-3 columns of small cycloid scales; with median scales being slightly larger; scaled area of caudal fin extended posteriorly, especially at upper and lower end, with minute, interradial scales, approximately up to one half of caudal fin; sixteen scales around caudal peduncle (Ref. 122085). Total vertebrae 29-31, excluding urostyle element, with 13-14 abdominal and 16-18 caudal vertebrae; pterygiophore supporting last dorsal-fin spine inserted between neural spines of 15th and 16th or 16th and 17th vertebra, counted from anterior to posterior; pterygiophore supporting last anal-fin spine is inserted between haemal spines of 15th and 16th vertebra or between rips of 14th and haemal spine of 15th vertebra; single predorsal bone present; hypurals 1 and 2 fused into either single, seamless unit or separated by clearly distinct seam; hypurals 3 and 4 always fused into single seamless unit (Ref. 122085).

Colouration: In life: body ground colouration brownish to greyish; dorsum, flanks and caudal peduncle greyish, beneath lower lateral line becoming yellowish; belly yellow; chest anteriorly whitish and remaining area yellow; dark grey interrupted midlateral band from eye, anteriorly extended midlateral band, to just behind caudal-fin base ending in well pigmented vertically elongated blotch; midlateral band crossed by 7-9 greyish vertical bars; at level of upper lateral line they sometimes fuse with each other forming dorso-lateral band sometimes interrupted and ending at posterior end of dorsal-fin; on ventral flank at level of pectoral fin vertical bars sometimes fuse to ventro-lateral band, less intensive then previous mentioned ones, that ends well before level of anus; iris dorsally yellow remaining greyish; dorsal head surface, ethmoidal area, preorbital area greyish; cheek greyish near eyes, yellowish below and with vertical stripe-like pattern centrally, less distinct than other stripes of face mask; preoperculum light greyish-yellow; operculum greyish, black opercular spot outlined with yellow; branchiostegal membrane brownish to orange; dark grey lachrymal stripe ending slightly anterior of caudal end upper lip; greyish nostril stripe caudally fused with lachrymal stripe, beneath eye; interorbital stripe greyish; no clearly defined supraorbital stripe or nape band but recognizable to some extent by darker, grey, colouration than remaining dorsal head surface; upper lip and lower lip yellow-orange; upper and lower margin of upper lip greyish; dorsal-fin membrane brownish, especially spinous part, to yellowish, soft rayed part; margin orange; brownish to dark greyish maculae from about posterior half of spiny part to end soft-rayed part arranged in several almost vertical columns; anal-fin membrane transparent proximally becoming yellowish distally, soft rayed part, margin of spiny and soft-rayed part black becoming yellow to brownish towards posterior tip; 3-6 orange eggspots, large orange centre surrounded by yellow concentring ring and outlined by more or less ill-defined transparent margin, on anal fin in both sexes; eggspots arranged into 1-2 rows, first eggspot located centrally on fin just behind last anal spine; caudal fin yellowish, orange distally, margin outlined in grey-black; caudal with brownish maculae arranged into 3-4 vertical columns; pectoral fin transparent, rays greyish; pelvic fin deep black, especially skin around spine, except for small yellow central portion of rayed area (Ref. 122085). Juvenile colouration in life: ground colouration beige, belly whitish; patterns and head mask as described for adults but less prominent; brown to greyish vertical bars on flank appear wider than in adults, dorso-lateral band and ventro-lateral band not visible; last vertical bar on caudal fin base roundish blotch extending onto caudal fin, not a vertical bar as in adults; dorsal fin brownish with several hyaline patches, margin not orange; anal fin light brownish-orange; no eggspots on anal fin present; caudal fin brownish-orange, no maculae present; pectoral fin hyaline; pelvic fin white to yellowish (Ref. 122085). In alcohol: colouration and melanin pattern similar to live specimens, due to preservation procedure of specimens, they tend to lose original colouration, especially melanin patterns more intense than in live specimens; overall body ground colouration brownish; dorsum and flank brownish becoming brighter ventrally; chest and belly light brown to beige ; branchiostegal membrane dark greyish; dorsal head surface brownish; ethmoidal area greyish brown; upper and lower lip beige; upper and lower margin of upper lip greyish brown; cheek light brown to brownish; cheek stripe dark brown; operculum dark brown becoming somewhat darker ventrally; with opercular spot as described above; head mask dark grey; midlateral band, vertical bars, dorso-lateral band and ventro-lateral band dark brown; dorsal fin greyish brown becoming greyish beige caudally, margin blackish with very fine black seam; maculae on spiny and soft-rayed part dark grey; anal fin beige with blackish distal margin and dark grey at posterior margin; eggspots on anal fin faded and not visible in preserved specimens; caudal fin beige to light greyish with dark greyish margin; maculae dark grey; pectoral fin beige to light grey; pelvic fin deep black except small central portion of rayed part greyish (Ref. 122085).