Induction of gonadal maturation at different temperatures in burbot Lota lota.

A rearing experiment was conducted to test whether temperature protocols that differed from a simulation of natural conditions might induce maturation after isothermal grow-out in burbot Lota lota. Lota lota were acclimated to two different temperature regimes: low temperature (LT), close to natural temperature at 4·0° C and elevated, high temperature (HT) at 8·5° C over 40 and 27 days respectively, with all fish then wintered for 47 days. Every second fish was treated with a gonadotropin-releasing hormone analogue.

Influence of temperature on puberty and maturation of pikeperch, Sander lucioperca.

Among external factors, temperature is known to exhibit a prominent role in reproduction of temperate fish species. Here, temperature related induction of puberty in pikeperch Sander lucioperca was investigated. For the first time the key factors of the pikeperch brain-pituitary-gonad axis, targeting the mRNA expression of the luteinising hormone (LH) and the follicle stimulating hormone (FSH), as well as the plasma sex steroids estradiol (E2), testosterone (T), 11-ketotestosteron (11-KT) and 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P) were addressed in the experiment.

Aqueous leaf extracts display endocrine activities in vitro and disrupt sexual differentiation of male Xenopus laevis tadpoles in vivo.

The occurrence of natural substances acting as endocrine disrupting compounds (EDC) in the environment is to date poorly understood. Therefore, (anti)androgenic and (anti)estrogenic activities of three different aqueous leaf extracts (beech, reed and oak) were analyzed in vitro using yeast androgen and estrogen screen. The most potent extract was selected for in vivo exposure of Xenopus laevis tadpoles to analyze the potential effects on development and reproductive biology of amphibians.

Endocrine disruption in aquatic vertebrates.

Environmental compounds can interfere with endocrine systems of wildlife and humans. The main sink of such substances, called endocrine disrupters (ED), are surface waters. Thus, aquatic vertebrates, such as fish and amphibians, are most endangered.