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

## TL;DR

This study explores how rising temperatures affect testis development in a type of fish called Thamnaconus septentrionalis, using transcriptomics to identify key genes and biological processes involved.

## Contribution

The study is the first to elucidate the molecular mechanisms of temperature-induced testis development in Thamnaconus septentrionalis.

## Key findings

- Rising temperatures enhance testis development in Thamnaconus septentrionalis.
- Transcriptomic analysis identified 315 differentially expressed genes, including those involved in steroid hormone biosynthesis.
- Upregulated genes like hsd11b2, cyp11b, cyp11a, and hsd17b3 may increase testosterone and 11-keto-testosterone levels.

## Abstract

Fish are rich in species and provide an important food supply, especially high-quality protein sources, for billions of people worldwide. In recent years, aquaculture production of fish has exceeded wild catch production, highlighting the importance of the fish aquaculture industry. As is well-known, regulating the reproductive processes of economically valuable fish is a critical step in artificial breeding. The gonadal development of many fish species, including the greenfin horse-faced filefish in this study, could be influenced by temperature. Thus, the present study first investigated the potential molecular mechanism of Thamnaconus septentrionalis testis development induced by temperature and found that the rising temperature enhanced its testis development. The major findings will provide a valuable and important theoretical and technical basis for the artificial breeding and fishery resources conservation of T. septentrionalis in the future.

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.