Monogonont rotifers constitute, depending on the moment of the year, most of the zooplankton in many freshwater ecosystems. Sexual reproduction is essential in the development cycle of these organisms as it enables them to constitute stocks of cysts which can withstand adverse environmental conditions and hatch when favorable conditions return. However, endocrine disrupting compounds (EDCs) can interfere with the reproduction of organisms. The present work aimed to investigate the effects of cyproterone acetate (CPA, anti-androgen and progestogen synthetic steroid) at 0.5 mg L-1, on the sexual reproduction of Brachionus calyciflorus in a cross-mating experiment. Results show no impact on mixis whereas the fertilization rate and resting egg production were higher in females exposed to CPA (from embryogenesis to adult stage), regardless of the treatment applied to the males with which they were mating (i.e. males hatched from CPA-treated females or from control females). Moreover, neonate females which mothers has been exposed to 0.5 mg L-1 CPA had more oocytes in their germarium than control neonates. Our results suggest that the effects of CPA observed are not related to toxicity but rather are consistent with an endocrine disruption-related impact, probably through disturbance of the mate recognition protein (MRP) production and through interference with a steroid receptor. Moreover, the absence of effect on mixis rate indicates that mixis induction on the one hand and mating process and resting production on the other hand are not controlled by the same hormonal pathways.
Keywords: Anti-androgen; Brachionus; Endocrine disruption; Progestogen; Rotifera; Sexual reproduction.