Effects of cadmium on gametogenesis in the sea star Asterias rubensL.

Abstract

The effects of cadmium on gametogenesis in the sea star Asterias rubens were studied after short-term exposure to 200 μg Cd/l or after long-term exposure to 25 μg Cd/l under semi-field conditions. Short-term exposure of female sea stars to cadmium caused a reduction in ovary growth. Part of the oocytes obtained from Cd-exposed females showed no germinal vesicle breakdown (GVBD) upon stimulation with 1-methyladenine, while the other part needed more time to complete GVBD than oocytes from unexposed sea stars. Histological study of the ovaries of exposed females revealed a growth delay in part of the oocytes. No effect of short-term cadmium exposure was found on growth of testes. Long-term exposure of sea stars to 25 μg Cd/l caused a delay in ovary growth. This effect was clear after five months of exposure, but at the end of the reproductive cycle the difference had become smaller. No effects were observed on the overall biochemical composition of the ovaries or oocytes. The cadmium concentration in oocytes of exposed sea stars was only about 30% lower than the level found in whole gonads. Gonadal growth in male sea stars was not affected by long-term cadmium exposure. The cadmium level in testes of Cd-exposed males was about a factor 6 lower than in ovaries. The cadmium concentration in spermatozoa was comparable to that of whole testes.