Effect of anti-androgenic substances on the sexual reproduction of the rotifer Brachionus calyciflorus.

Many substances released in the aquatic environment have been reported to have disruptive effects on endocrine systems of vertebrates and invertebrates. In rotifers, some of these chemicals have been shown to depress sexual reproduction at concentrations one to two orders of magnitude below those that affect asexual reproduction. The anti-androgen flutamide impacts sexual reproduction of rotifers at particularly low concentrations. We studied the effect of different types of putative endocrine disruptors on sexual reproduction of Brachionus calyciflorus. Contaminants tested were cyproterone acetate, an anti-androgen with a steroid-like structure, the pesticides fenitrothion and linuron which both have high affinity to the androgen receptor in vertebrates, although they are nonsteroidal molecules, and lindane a widely used pesticide that binds weakly to the androgen receptor in vertebrates. A series of endpoints relative to different steps of sexual reproduction were monitored to define critical functions affected and to get information on mechanisms of action. Fenitrothion, had the strongest impact on the sexual reproduction of rotifers. We observed a decrease in the proportion of mictic females among the ovigerous individuals and in the production of fertilized eggs per female that was proportional to the dose. The most sensitive parameter was the number of males produced per mictic female which was considerably higher in treated animals even at concentrations 10 times lower than the NOEC of asexual reproduction.