- Article
Water temperature critically influences growth and gonadal development in teleosts, yet its effects on adult black scraper (Thamnaconus modestus) remain unclear. To address this, 590-day-old T. modestus were reared for 4 months under three thermal regimes: natural ambient temperature (control, CG), or constant 21 °C (T21) or 24 °C (T24). Growth indices were measured monthly. Gonadal development was assessed histologically, and serum 17β-estradiol (E2), testosterone (T), FSH, and LH levels were quantified by ELISA. Heat stress responses were further examined at 24 °C, 27 °C, and 30 °C. Gill and liver tissues were analyzed histologically, and HSP70 mRNA (qRT-PCR) and protein (Western blot) expression were measured. The results showed that after 120 days, growth indices in both sexes from the T21 group were significantly higher than in the control (CG) and T24 groups (p < 0.05). The gonadosomatic (GSI) and hepatosomatic (HSI) indices were also highest in the T21 group. In females, oocytes in the T21 and T24 groups reached the secondary and tertiary yolk stages, respectively; in males, testes advanced to the spermatid and spermatozoon stages, respectively. By contrast, CG fish remained in the yolk vesicle and secondary spermatocyte stages, indicating that constant exposure to 21 °C or 24 °C accelerates gonadal maturation in T. modestus. At day 120, E2 and FSH levels in females from T21 and T24 were significantly higher than in CG (p < 0.05). In males, FSH and LH levels in T24 exceeded those in CG (p < 0.05). These hormonal changes suggest E2 and FSH drive female maturation, while FSH and LH are key for male maturation. Furthermore, heat stress experiments showed that 27 °C and 30 °C, compared with 24 °C, caused histopathological damage in gill and liver tissues. Concurrently, HSP70 mRNA and protein levels were significantly upregulated in gills (p < 0.05), indicating that thermal stress impaired gill and liver integrity and altered HSP70 expression in these tissues. Collectively, compared with the nature temperature, 21 °C and 24 °C supported fast growth and sexual maturation, whereas 27 °C and 30 °C induced significant tissue damage in T. modestus.
14 November 2026



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