Embryonic and larval development of an endangered catfish, Horabagrus brachysoma

The fertilised eggs of Asian sun catfish, Horabagrus brachysoma (Gunther 1864) were demersal and pale yellow in colour with equal perivitelline space. First cleavage appeared at 49 min (+/- 3 min) and the size of the blastomeres reduced as the development stage proceeded. Morula stage was reached 3 h 37 min (+/- 15 min) post-fertilization. The embryonic development from morula to hatching took about 16-17 h. The hatching of eggs started at 20 h 46 min (+/- 28 min) post-fertilization. The newly hatched yolk-sac larvae were 3-4 mm in length. A membranous layer was found covering from behind the head to posterior part of yolk-sac. Eye, mouth, alimentary canal, barbells and pectoral fins were appeared in the 3 days after hatch (dah). The membranous layer started rupturing at fifth day of post-hatch and disappeared during 9-12 dah with the appearance of fins in different parts of body. Pigments on dorsal side of body appeared in 2 dah larvae and the 10-12 dah larva looked pale brown in colour. After 12 dah, the larva morphologically resembled like an adult fish.