Understanding early development: a detailed study of Clarias dussumieri (Valenciennes, 1840), a near-threatened catfish of the Western Ghats

Summary The study documents the embryonic and larval development of Clarias dussumieri , a Near-Threatened, cultivable, and highly valued food fish endemic to the Western Ghats. Induced breeding facilitated detailed observation of developmental stages using light microscopy. Unfertilized eggs measured 1.5 ± 0.02 mm in diameter and enlarged to 1.7 ± 0.10 mm after fertilization (∼13% increase). The first cleavage occurred at 00:36 ± 00:02 h, reaching 64 cells by 01:35 ± 00:06 h. Epiboly progressed from 30% at 03:20 ± 00:10 h to 50% at 04:30 ± 00:05 h and 90% at 05:50 ± 00:10 h; neurulation was evident by 07:40 ± 01:10 h and somites by 11:08 ± 01:26 h. The first heartbeat appeared during the pharyngula period (17:25 ± 01:30 h), and hatching occurred at 25:30 ± 01:30 h at 26–27°C. Hatched larvae were 4.2 ± 0.02 mm total length, observed few melanophores by 12 h, conspicuous eye pigmentation by 24 h, and body pigmentation spreading by day 2 (5.90 ± 0.04 mm).The yolk sac was fully absorbed by 72 ± 2.50 h post-hatching, marking the onset of exogenous feeding. By day 4 (pre-flexion), larvae reached 7.1 ± 0.02 mm; initial notochord flexion began around day 7 and post-flexion from day 10, with juvenile-like morphology evident by day 25 (15.27–17.80 mm). The standardized timelines and measurements provide a baseline for hatchery practice and conservation aquaculture of C. dussumieri , supporting protocol refinement for improving survival and growth under controlled conditions