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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

The present study demonstrates chromatography techniques for purifying immunoglobulin (Ig) from the serum of two fish species, Clarias dussumieri and Etroplus suratensis . Four purification techniques including BSA-affinity chromatography, protein-A affinity chromatography, protein-L affinity chromatography, and ammonium sulfate precipitation followed by ion-exchange chromatography were evaluated. Subsequently, the purified proteins were analysed using SDS-PAGE, gel chromatography and ESI-nano-LC-MS/MS. BSA-affinity chromatography stands out as a versatile and highly effective technique for purifying Ig from both the fish species. Despite the successful isolation of serum Ig using ammonium sulfate precipitation followed by ion-exchange chromatography for both fish species, SDS-PAGE analysis revealed non-specific protein bands and protein-A and protein-L affinity chromatography failed for purification. The purified Ig displayed distinctive profiles, with C. dussumieri showing a heavy chain of ~70 kDa and a light chain of ~25 kDa, while E. suratensis exhibited a heavy chain of ~72 kDa and a light chain of ~28 kDa. Gel filtration chromatography indicated native molecular weights of Ig approximately ~803 kDa for C. dussumieri and ~855 kDa for E. suratensis . Further characterization of heavy chain bands through ESI-nano-LC-MS/MS confirmed homology matches with Ig proteins. This study enhances fish Ig purification protocols, laying the groundwork for future research to refine and expand methodologies essential for sero-diagnostic applications in aquaculture.

Clarias dussumieri , a near threatened freshwater catfish, is endemic to peninsular India and has aquaculture potential. Unlike its sister species, C. magur , the male fish needs not be sacrificed during captive breeding. Thus, the generation of genomic information of this species becomes significant for effective genome mining through the bioprospecting of novel genes for important production traits. In this study, the genome assembly was undertaken to address this gap by generating high quality chromosome level genome assembly using PacBio long reads and Hi-C scaffolding. The total assembled genome was found to be 918.72 Mb in size and showed 95.23% completeness. Its characterization exhibited 41.46% repeats, 1,174,725 SSRs and 25,369 predicted genes with functional annotations. The Single copy orthologs analysis placed C. dussumieri in a distinct position with C. magur . The comprehensive genomic information offers resources for comparative genomics with other Clarias species for improvement of economic traits.