Prosobranch snails as test organisms for the assessment of endocrine active chemicals -: an overview and a guideline proposal for a reproduction test with the freshwater mudsnail Potamopyrgus antipodarum

Recently, prosobranch snails have been recommended as promising candidates for test organisms for the assessment of endocrine active chemicals. Three prosobranch snail species, the freshwater mudsnail Potamopyrgus antipodarum, the freshwater ramshorn snail Marisa cornuarietis, and the marine netted whelk Nassarius reticulatus are portrayed and their respective biotests are presented together with results of laboratory experiments and biological effect monitoring surveys in the field. All characterized species are highly sensitive toward xeno-androgens [triphenyltin (TPT), tributyltin (TBT), methyltestosterone (MT) and fenarimol (FEN)], and xeno-estrogens [bisphenol A (BPA), octylphenol (OP), ethinylestradiol], and show effects at environmentally relevant, rather low concentrations in laboratory experiments. For exposure to the xeno-androgen TPT, EC10 values range between 15.9 and 29.0 ng as Sn/L (sediment 0.03 mu g as Sn/kg), for TBT, EC10 values are found between 3.42 and 37.8 ng as Sn/L (sediment 2.98 mu g as Sn/kg) and effect concentrations for FEN are calculated as 18.6 ng/L (EC10) and 0.19 mu g/kg (EC50 sediment; EC10 not calculable). Exposure to xeno-estrogens yielded EC10 values of 13.9 ng/L (0.19 mu g/kg) for BPA, a NOEC of < 1 mu g/L (EC10 of 0.004 mu g/kg) for OP and a NOEC of 1 ng/l (EC10 sediment of 2.2 mu g/kg) for ethinylestradiol. Responses to androgens comprised the development of imposex and the reduction of fertility or embryo production, effects of estrogens included the stimulation of egg production and embryo production, and the increased weight of glands. Also, biological effect monitoring studies with P. antipodarum and N. reticulatus in several rivers or estuarine areas revealed the capacity of the biotests to detect an androgenic or estrogenic potential of sediment samples. A comparison of the three test species with regard to sensitivity and practical aspects in routine application favors the freshwater mudsnail P. antipodarum for a standardized procedure, and this reproduction test will be introduced into the OECD guideline program for standardization in the near future.