Evaluation of Gonadal Gene Expression in Himalayan Snow Trout <i>Schizothorax plagiostomus</i> during Annual Reproductive Cycle

The snow-trout Schizothorax is a prevalent food fish found in the cold water bodies of Hindukush- Karakoram- Himalayan mountains/foothills and is one of the major sources of animal protein. During the past decade, there has been a rapid fall in the Schizothoracine population due to climate change with unrestricted urbanization and other anthropogenic interventions. Therefore, an in-depth understanding of the annual gonadal development in these fish taxa becomes critically essential for designing appropriate/suitable conservation strategies. Like most freshwater teleosts, hill-stream fishes are typical seasonal breeders. In the current study, the season-dependent developmental gene expression was examined in adult S. plagiostomus gonads (both testes and ovaries) obtained from a natural habitat at Garhwal, Uttarakhand, India. A total of six putative genes (three testicular and three ovarian) were investigated in three different developmental stages, keeping the β-actin gene as the endogenous reference. Our data suggested that Dmrt1 and Gdnfr-α mRNAs were highly elevated during the pre-spawning stage, gradually down-regulated during the spawning stage, and almost undetectable at the post-spawning stage. However, in contrast, Fgf11 was found to be augmented during the spawning stage. On the contrary, Foxl2 and Runx1 transcripts were elevated during pre-spawning and spawning stages compared to those found during post-spawning stages. Finally, Gdf9 mRNA was found to be maximal at the pre-spawning stage and subsequently diminished during the spawning stages. This is the first comparative gonadal transcriptomic data showing the season-dependent developmental gene expressions critically regulating the optimal gametogenic drive/output in any Schizothoracine fish. This study provides fundamental information regarding the gonadal biology of Schizothorax, which will be supportive of designing suitable artificial breeding/conservation programs for this species in the future.