Deleterious impacts of heat stress on steroidogenesis markers, immunity status and ovarian tissue of Nile tilapia (Oreochromis niloticus)

• Published in: Journal of thermal biology Vol. 91; pp. 102578 - 9
• Main Authors: Mahmoud, Shawky, Sabry, Asmaa, Abdelaziz, Ahmed, Shukry, Mustafa
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-07-2020; Elsevier BV
• Subjects: 17β-Estradiol; Acclimatization; Aquaculture; Cortisol; Gene expression; Heat shock proteins; Heat stress; Hsp70 protein; Immunity; Immunity (Disease); Lysozyme; Nile tilapia; Oreochromis niloticus; Phagocytes; Ponds; Serum levels; STAR; Star protein; Steroidogenesis; Steroidogenic acute regulatory protein; Thyroid hormones; Thyroxine; Tilapia; Triiodothyronine; Vitellogenin; Water temperature; Heat stress; STAR; Vitellogenin; Nile tilapia; Immunity
• ISSN: 0306-4565; 1879-0992
• DOI: 10.1016/j.jtherbio.2020.102578

The water temperature of aquacultures is a primary factor of fish welfare, reproductive patterns, and immunity. To elucidate the molecular and biological processes of the temperature modulation of reproduction and immunity, female Nile tilapia (190 ± 10g) were allocated into five groups following acclimatization (150 females, three replicates, each n = 10). Each group was subjected to various temperatures (28 °C, 30 °C, 32 °C, 34 °C, and 37 °C), the group at 28 °C representing the control. Their serum levels of estradiol, cortisol, and vitellogenin were measured as well as serum triiodothyronine (T3) hormone, thyroxine (T4) hormone, and non-specific immunity (phagocytic and lysozyme activity). In addition, steroidogenic acute regulatory protein (STAR), vitellogenin gene receptor, and heat shock protein 70 (HSP70) gene expression were evaluated. The serum levels of estradiol, cortisol, and vitellogenin markedly declined (P < 0.05) in fish group at higher temperatures. In addition to T3, T4 was significantly affected (P < 0.05) in the control group. The expressions of the STAR gene (steroidogenesis) and vitellogenin receptors were also considerably down-regulated. The histopathological photomicrograph of fish subjected to high water temperature revealed injuries in ovary tissues, demonstrating its harmful effects. The experimental results verified the possible role of water temperature as a main stressor on Nile tilapia’ physiology through modulation of steroidogenesis-related gene expression and immunity.
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•This study explores the impact of heat stress on Nile tilapia (Oreochromis niloticus) reproductive and immunity status.•Fish imperiled at high temperatures showed significant declines in estradiol, cortisol and vitellogenin (P < 0.05).•High water temperatures displayed degenerative changes in fish ovarian tissues and some reproductive modulator gene.•The results obtained verified that water temperature is one of the key stressors influencing Nile tilapia's health status.