The elasmobranchs (sharks, rays and skates) being the extant survivors of one of the earliest offshoots of the vertebrate evolutionary tree are good model organisms to study the primitive vertebrate conditions. They play a significant role in maintaining the ecological balance and have high economic value. Due to over-exploitation and illegal fishing worldwide, the elasmobranch stocks are being decimated at an alarming rate. Appropriate management measures are necessary for restoring depleted elasmobranch stocks. One approach for restoring stocks is implementation of conservation measures and these measures can be formulated effectively by knowing the evolutionary relationship among the elasmobranchs. In this study, a total of 30 species were chosen for molecular phylogeny studies using mitochondrial cytochrome c oxidase subunit I, 12S ribosomal RNA gene and nuclear Internal Transcribed Spacer 2. Among different genes, the combined dataset of COI and 12S rRNA resulted in a well resolved tree topology with significant bootstrap/posterior probabilities values. The results supported the reciprocal monophyly of sharks and batoids. Within Galeomorphii, Heterodontiformes (bullhead sharks) formed as a sister group to Lamniformes (mackerel sharks): Orectolobiformes (carpet sharks) and to Carcharhiniformes (ground sharks). Within batoids, the Myliobatiformes formed a monophyly group while Pristiformes (sawfishes) and Rhinobatiformes (guitar fishes) formed a sister group to all other batoids.

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The giant river catfish Sperata seenghala has huge demand in South Asian countries due to its low number of intramuscular bones and nutritive value. However, the culture practises for this fish have not been standardized and the current demand for this fish is being met by capture fisheries only. Unregulated and indiscriminate fishing would lead overexploitation of fish stocks subsequently stock depletion. Genetic diversity between populations would give insight about population structure and demography. In the present study, S. seenghala stocks from three rivers, namely Ganga, Brahmaputra and Mahanadi were characterized using cytochrome b gene and D-loop region. Moderate to high haplotype diversity and low nucleotide diversity values were observed in all populations. Analysis of molecular variance and pairwise F values showed significant genetic differentiation among populations. Patterns of diversity, haplotype networks and mismatch distribution strongly suggest a historical influence on the genetic structure of S. seenghala populations. S. seenghala stocks from these three rivers are genetically distinct units and management measures should be formulated separately for each population.

Gobiids constitute a major proportion of fish population in both tropical and temperate freshwater as well as marine ecosystem. Due to their small size, cryptic ecology and ambiguous morphological characters, gobiids diversity was not documented completely. In this study, DNA barcodes were generated for 11 species of gobiids, collected from the Ashtamudi Lake, India. The mitochondrial COI gene was amplified using universal primers and the resulted 650 bp amplicon was sequenced. The COI barcodes clearly distinguished all the species with high interspecific genetic distance values than intra-specific values based on K2P (Kimura 2 Parameter) model. The average genetic distance (K2P model) within species, genus and family was 1.2%, 22.2% and 25.3%, respectively. In addition to barcode-based species identification system, Nucleotide Diagnostic (ND) characters specific for species were identified. The Neighbor-Joining tree revealed distinct clusters shared by the species of same genera.

Morphotypic differentiation is the external manifestation of dominance hierarchy in The intermediate morphotype orange claw (OC) male exhibits the highest growth rate and is subordinate in hierarchy to blue claw (BC) male while dominant on small male (SM). The present study was undertaken to examine the specific role of insulin-like androgenic gland () hormone in morphotype differentiation of To achieve this, RNAi mediated knockdown as well as augmentation of transcripts were effected in ∼60 g OC males using plasmid-based constructs pcD-IAG-lh and pcD-IAGorf, respectively. The treatments were administered to animals maintained in isolation as well as in community. The knockdown plasmid construct that expresses -specific long hairpin RNA caused 16-fold reduction of transcripts in the SSN1 cell line When injected into OC males living in a community, 2.3-fold knockdown was recorded, while in isolated OC males it was 4.2-fold initially, but returned to normal subsequently. Compared with the respective controls, OC to BC transformations in the silenced animals were significantly lower in the community-reared group, while no difference was observed in the isolated animals. It is reported here for the first time that augmentation in OC males resulted in significantly higher OC to BC transformations, when animals were reared in community. This plasmid-based IAG knockdown approach could be developed into a low stress, feed or immersion treatment for controlling heterogeneous individual growth of males in aquaculture.

The giant river-catfish Sperata seenghala is one of the commercially important freshwater catfishes of India with wide distribution in all major rivers and reservoirs. This fish has huge demand in domestic market due to high nutritional value and low number of intramuscular bones. Conversely, the culture practices for this fish have not yet been standardized and capture fisheries is the only source to meet the demand. This may lead to over exploitation of resources and subsequent population reduction. Knowledge on genetic structure of populations is prerequisite to formulate sustainable management and conservation measures. In the present study, 15 microsatellites were used to characterize population genetics of S. seenghala collected from river Brahmaputra, Ganga, Godavari, Mahanadi and Narmada. Locus-wise, the number of alleles varied from 8 to 19 with an average of 12 alleles per locus. The mean observed and expected heterozygosity values varied from 0.622 to 0.699 and 0.733 to 0.774, respectively. Several loci have shown deviation from Hardy–Weinberg equilibrium and no significant linkage disequilibrium between pairs of loci was detected. Pair-wise FST values between populations ranged from 0.135 (Brahmaputra–Ganga) to 0.173 (Brahmaputra–Narmada) and confirmed the moderate to high genetic differentiation among the populations. AMOVA, Structure and Principal Co-ordinate analyses showed significant genetic differentiation among the sampled populations of S. seenghala. A total of 65 private alleles were recorded across populations. This study confirmed the distinctiveness of each population of S. seenghala from five major rivers of India. These populations could be treated as distinct management units (MUs) for assessment and management purpose.