Oogenesis inhibition, plasma steroid levels, and morphometric changes in the hypophysis in Russian sturgeon ( Acipenser gueldenstaedti Brandt) exposed to low environmental pH

Abstract

Juvenile (5.5–6.5 months old) Russian sturgeon exposed to pH levels of 4.0–4.8 for 25 days were compared to control fish kept at pH levels of 7.2–7.6. By the end of the experiment, the body mass had decreased by 13% in the low pH-exposed fish, whereas the body mass was increased by 16% in the control fish. In the treatment females, the sex cells fund grew more (as means number of oogonia), but the initiation of sexual differentiation was retarded. Statistically significant increases in plasma testosterone concentration were observed in treatment fish at the beginning of the low pH exposure, and in the control females during cytological differentiation. No sex differences in estradiol-17 β concentration were found. The adenohypophyseal gonadotropical region was more active in females than in the males. The percentage of granulated hypophysial gonadotrops appeared to be higher in the treatment females than the control females at the beginning of the low pH exposure. These responses are attributed to an adaptation response in the low pH-exposed fish and to sexual differentiation in both treatment and control females.