Effect of short-term intermittent exposure to estradiol on fish reproductive physiology

What is it about?

The objective of this study was to determine how the short-term exposure to a supraphysiological concentration of waterborne 17β-estradiol (E2) influences on melatonin (Mel) and thyroxine (T4) concentrations in plasma and E2 and 11-ketotestosterone (11-KT) concentrations in plasma and gonads in both sexes of round goby (Neogobius melanostomus) during the pre-spawning, spawning, late spawning and non-spawning phases. The experimental protocol was based on short-term, repeated exposures of fish to a supraphysiological dose of waterborne E2. Mel level was unchanged on exposure to E2 during the investigated phases, and its role in determining a time frame for spawning in both sexes of round goby seems to be stable in those conditions. T4 and sex steroids (E2 and 11-KT) were sensitive to the exposure of E2, and those changes influence gonads by accelerating oocyte development, ovulation and regression and inhibiting spermatogenesis in this species. The results demonstrate that the physiological responses of fish in all investigated phases were altered over a short window of exposure, indicating that short-term exposure to a supraphysiological dose of E2 may impact fish in the wild. Furthermore, round goby can be recommended as a very suitable model for studying endocrine disruptors, which is sensitive to even short exposure to E2.

Featured Image

Why is it important?

This is the first study to determine the influence of short-term, intermittent exposure to a supraphysiological concentration of waterborne E2 on Mel and T4 concentrations in plasma and E2 and 11-KT concentrations in plasma and gonads, supported by histological analysis of gonads, in both sexes of N. melanostomus during the reproductive cycle. In the present study, Mel level is unchanged in the short time exposure to a supraphysiological dose of E2 during investigated phases and its role in determining a time frame for spawning in N. melanostomus females and males seems to be stable in those conditions. It should be noted that this stable level of Mel can protect against serious histopathological changes in gonads as a consequence of E2 exposure. However, T4 and sex steroids (E2 and 11-KT) were sensitive to even short exposure to E2. It is possible that T4 and sex steroids are integral in affecting the gonads of N. melanostomus by hastening oocyte development, ovulation and regression and inhibiting spermatogenesis in response to exogenous E2 during the reproductive cycle. It seems that hormonal changes due to estradiol exposure cause greater disturbances in the reproduction of males than females. In males, there is shortening spawning and fertility disturbances. In turn, in females, the acceleration in oocyte development, ovulation and regression may paradoxically enhance their reproductive potential.

Perspectives