Sabine Schäfer

• Environmental contaminants are suspected to impair reproductive health of exposed organisms. In the present study, the effects of environmental contaminants on gonadal biology of adult sea urchins as well as cellular events in sea urchin eggs during fertilization were investigated. Female Psammechinus. miliaris exposed to a high dose (500 µg L-1) of the polycylic aromatic hydrocarbon phenanthrene for 20 days showed severe gonadal lesions which are similar to histopathological changes in other invertebrates as well as in fish following exposure to PAHs or oil. High (150 µg L-1) and environmentally relevant (5 µg L-1) concentrations of phenanthrene on reproductive tissue induced either no or only minor histological and biochemical changes in the gonads. But, profound sex-specific differences indicate that testes are much more susceptible to oxidative stress than ovaries. Samples from a population of P. miliaris in the northern Wadden Sea showed that sex, gonadal stage and spawning affect gonadal histology and histochemistry. Phenanthrene as well as various other chemicals is known to interfere with cellular calcium signalling. One of the best studied Ca2+ signals and essential for successful reproduction is the Ca2+ wave at fertilization. For the first time, the Ca2+ signal at fertilization was recorded using the Ca2+ indicator dye Fura-2 acetoxymethylester (AM) in combination with MK571, an inhibitor of multidrug resistance associated proteins. The metal copper and the brominated compound 2,4,6-tribromophenol (TBP) significantly increased the fertilization Ca2+ signal in P. miliaris at 6.3 µM and 100 µM, respectively, which might contribute to the observed reduced fertilization rates following exposure to these compounds. The shown histopathological and cellular investigations provide a promising basis for future studies on pollutant-induced reproductive disorders not only in sea urchins but also in other invertebrates.