Effects of temperature on growth performance, antioxidant capacity, ovary development and gene expression in Micropterus salmoides

Temperature plays a crucial role in the gonadal development and maturation of fish. However, the mechanism by which fish perceive temperature signals and respond accordingly, thereby altering their developmental trajectory, remains incompletely understood. In this study, the largemouth bass (LMB) broodstock were reared at ambient temperature, 18℃, 23℃ and 28℃ for 60 days respectively. The growth differences, antioxidant capacity, serum hormones and ovarian development were compared, and comparative transcriptome analyses of ovarian tissues were performed. The results revealed that the weight gain (WG, %), specific growth rate (SGR, %/day), and gonadosomatic index (GSI, %) of LMB at 18℃ were significantly higher than those in other groups ( p < 0.05). Compared to the control group under natural water temperature, fish maintained at constant temperatures (18 °C, 23 °C and 28 °C) exhibited significantly higher activities of total antioxidant capacity (T-SOD) and catalase (CAT), along with a markedly lower malondialdehyde (MDA) content. Histological analysis showed that under 18℃ and 23℃ conditions, most oocytes were in the vitellogenic stage, while oocytes in the 28℃ group were mainly in the primary growth stage and cortical vesicle stage, with some oocytes atretic. Additionally, transcriptome sequencing detected a total of 30,523 genes, and comparative analysis found 854, 1344, 1823, 322, 1400, and 1349 DEGs in 18℃ vs control, 23℃ vs control, 28℃ vs control, 23℃ vs 18℃, 28℃ vs 18℃, and 28℃ vs 23℃, respectively. KEGG analysis revealed that these DEGs were mainly enriched in pyruvate metabolism, thermogenesis, apelin signaling pathway, PPAR signaling pathway, GnRH signaling pathway, ovarian steroid biosynthesis, PI3K-AKT, TGF-β signaling pathway, prolactin signaling pathway. The results can provide a reference for a deeper understanding of the molecular mechanism by which temperature regulates the gonadal maturation of fish, and also contribute to the analysis of the mechanism of environment-gene interaction. • Growth and antioxidant capacity in largemouth bass are significantly affected by different temperature. • Temperature altered serum hormones and ovary development of largemouth bass broodstock. • Transcriptomics revealed enrichment of pathways in energy metabolism and reproductive regulation under temperature stress.