Transcriptomics Analysis of Testis Development in Thamnaconus septentrionalis Responding to a Rise in Temperature

Thamnaconus septentrionalis is an emerging commercially important aquaculture species in China, distributed extensively in the Indo-West Pacific Ocean. Recently, because of the seriously declining population and considerable economic potential of this aquaculture fish, increasing attention has been paid to the conservation and development of T. septentrionalis. Artificial fish breeding is essential and has become progressively implemented on local farms in China, which benefits the protection of T. septentrionalis resources and facilitates the development of its fishery industry. Previous studies have demonstrated that temperature could significantly influence ovary development in T. septentrionalis. However, the potential molecular mechanisms underlying the influence of temperature on testis development in T. septentrionalis have been scarcely studied. Thus, this study comprehensively explores the effects of temperature on testis development in T. septentrionalis using histological observation and transcriptomic techniques. Histological and transmission electron microscopy analyses indicated that T. septentrionalis testes, undergoing a rise in temperature, developed from phase III to IV. Transcriptomic analysis identified 315 differentially expressed genes, including 200 upregulated and 115 downregulated genes. Moreover, rising temperatures may enhance testis development by regulating steroid hormone biosynthesis, cellular senescence, and nucleotide metabolism. The upregulation of four genes (hsd11b2, cyp11b, cyp11a, and hsd17b3) involved in the steroid hormone biosynthesis process may significantly contribute to the increased level of testosterone and 11-keto-testosterone. This study is the first to elucidate the potential molecular mechanism involved in T. septentrionalis testis development induced by temperature, offering valuable and novel insights for its artificial breeding and fishery resources conservation.