Diagnosis: Bathyaethiops baka is distinguished from all congeners by an incomplete squamation with the scale cover variably reduced to no pre-dorsal scales, usually no scales on caudal peduncle, and usually a scale-free patch on middle flank at about level of pelvic-fin origin; furthermore distinguished by a unique colour pattern, i.e., a combination of a humeral spot of about pupil-size and the absence of dark vertical bars along midlateral flanks (Ref. 110423). It is difficult to distinguish from juvenile Bathyaethiops caudomaculatus, from which it differs by the usually absence of unicuspid teeth in the second row of lower jaws vs. presence, and usually the absent or rudimentary supraneural between two neural spines directly in front of the first dorsal fin pterygiophore vs. well developed (Ref. 110423).

Description: A comparatively small species, maximum size 24.4 mm standard length; body laterally compressed, slightly elevated (Ref. 110423). Dorsal fin originating midway along body; pelvic fins originating slightly in front of dorsal fin; anal fin originating approximately at level of end of dorsal-fin base; adipose fin originating at level of caudal end of anal-fin base, positioned closer to caudal than to dorsal fin (Ref. 110423). Scale cover variably reduced; no pre-dorsal scales; usually no scales on caudal peduncle; usually a scale free patch on middle of flank at level of pelvic-fin origin; number of pored scales in lateral line variable, 0-9; lateral line never complete (Ref. 110423). Premaxilla with two teeth in outer row, each with three major and two minor cusps and four teeth in inner row with four cusps in the first, six cusps in the second and third, and seven cusps in the last tooth; dentary with four teeth in outer row, each with six cusps, except the last with only five cusps; an inner single monocuspid tooth usually absent (Ref. 110423). Pectoral fin with 12 rays with dorsalmost and ventralmost rays unbranched; pelvic fin with 8 rays, with first and last rays unbranched; 2 hypurals in lower lobe and 4 hypurals in upper lobe; 3 epurals; small cartilage present in front of anterior-most haemal spine (Ref. 110423). Supraneural directly in front of first pterygiophore of dorsal fin reduced in size or absent (Ref. 110423).

Colouration: In life: body pale translucent; dorsal, adipose and caudal fin bright red; pelvic and anal fin light orange to yellow; pectoral fin yellowish; upper quarter of iris orange; caudal peduncle on its dorsal and ventral margin slightly red; a prominent humeral spot the size of the pupil or larger, and a slightly larger dark spot on the caudal peduncle; the latter is bisected by a dark line along the midlateral line starting slightly in front of dorsal-fin origin and terminating just distal to the caudal peduncle spot; never any vertical stripes or barring along the midlateral line; few melanophores in mid-dorsal line along the back starting on lower jaw and reaching caudal peduncle; thin line of melanophores along anal-fin base; often an elevated line of melanophores proximal to the anal-fin base; a dark bar at the end of the caudal peduncle; melanophores densely set on posterior dorsal half of head; in general, contrast and colouration more pronounced in mature males (Ref. 110423). In preservative: pale whitish to light brown; red, orange and yellow colouration absent; melanophore pattern as in life specimens, but spot on the caudal peduncle less pronounced and smaller, i.e. not reaching the anal fin base; humeral spot more intensively coloured but of same size (Ref. 110423).