Reproductive effects in two species of native freshwater gastropod mollusc exposed to 17β-oestradiol or an environmentally relevant mixture of oestrogenic chemicals in outdoor mesocosms

摘要

Recent evidence suggests that molluscs may be sensitive to the effects of endocrine disrupting chemicals (EDCs) in a similar manner to vertebrates, such as fish. Despite this (with the exception of TBT-induced imposex in marine gastropods), molluscs have been largely overlooked in the field of endocrine disruption. Life-cycle studies were conducted in which two species of native UK freshwater gastropod molluscs (the hermaphrodite Planorbarius corneus and the gonochorist Viviparus viviparus) were exposed to either 17β-oestradiol or environmentally relevant mixtures of chemicals known to be oestrogenic to vertebrates and to be present in UK treated sewage effluents (TSE) and rivers. Adult snails were exposed for four months in outdoor mesocosms, fed by river water, over the spring and summer (breeding season) in order to examine effects on reproductive output, growth and mortality. Furthermore, offspring (F1s) were also developmentally exposed over the same period. F1 juvenile snails were then depurated in river water for nine months (over winter) after which time their growth, survival, and reproductive success were measured in further un-dosed river water mesocosm studies in the following spring/summer. Histopathology was used to determine immediate effects of chemical exposure on adult and F1 snails’ reproductive health. Histopathology was also used to determine long lasting effects of chemical exposure on depurated F1s. Exposure to oestrogenic chemicals resulted in a range of effects, including modulated fecundity and growth in F0 adults, to retardation of growth, sexual development and fecundity in developmentally exposed F1s. Exposure to mixtures of oestrogenic chemicals also resulted in possible modulation of the immune system, resulting in increased parasitism and over winter mortality of exposed F1s compared to snails exposed to river water alone. Differences in sensitivity and response to exposure between the two species and the generations were also observed.