Thyroid and Sex Steroid Hormones of Immature and Precocious Brown Trout Salmo trutta

• Published in: Biology bulletin of the Russian Academy of Sciences 2023-02, Vol.50 (1), p.1-7
• Main Authors: Ganzha, E. V., Pavlov, E. D., Ruchiev, M. A., Pavlov, D. S.
• Format: Article
• Language: English
• Subjects: 17β-Estradiol; Biochemistry; Biomedical and Life Sciences; Body length; Cell Biology; Ecology; Hormones; Life Sciences; Males; Salmo trutta; Sexual maturity; Steroid hormones; Steroids; Testosterone; Thyroid; Thyroid gland; Thyroid hormones; Thyroxine; Triiodothyronine; Trout; Zoology
• ISSN: 1062-3590; 1608-3059
• DOI: 10.1134/S1062359023010053

The concentrations of thyroid and sex steroid hormones in the blood of immature and precocious brown trout Salmo trutta at the final stage (age 1+, 2+) of the formation of early maturing fishes in the population were determined. The formation period of precocious males varied in different years in the Alatsoya River (Karelia); fish reached sexual maturity at ages 1+ or 2+. Immature and precocious fish at ages 1+ and 2+ do not differ in the concentrations of free and total triiodothyronine, of free thyroxine. Immature females and males at ages 1+ and 2+ also do not differ in the concentrations of sex steroid hormones. In contrast to immature brown trout, precocious males at age 2+ were characterized by an increased concentration of testosterone and decreased level of estradiol-17β in the blood. It has been established that the final stage in the formation of precocious fish in the population was characterized by the poor involvement of the thyroid gland in the maturation process of males and a significant decrease (by four times) in the rate of conversion of testosterone to estradiol-17β. This transformation in all studied females and males of brown trout was associated with their body length: the rate of conversion of estradiol-17β was increased with body length growth.