Pethia didi Pethia didi Pethia didi is a species of cyprinid fish which has only been recorded in the vicinity of Myitkyina and Indawgyi Lake in the north of Myanmar. This is a small fish which can reach a length of SL. It is generally brownish with a dark vertical bar just behind the operculum and a round dark blotch on the caudal peduncle. The species "P. tiantian" – with a range close to "P. didi" – is similarly marked, but "P. didi" can be distinguished by its truncated lateral line, deeper body and longer dorsal fin, with two rows of dark
Whitefin dogfish is distinctive in being the only "Centroscyllium" species with abrupt black markings beneath its head, trunk, and pectoral fins, with a black stripe running from under the caudal peduncle to over the pelvic fins. These markings are in fact concentrations of tiny light-emitting photophores. Unusually, this shark also has photophores along the undersides of its upper eyelids. What function these structures could serve is unclear; Tchernavin speculated that they could be used to illuminate prey or stimulate the eye. The rest of the body is gray-brown, with white fin margins. There are numerous small cone-shaped, hooked prickles over the body,