Endocrine disruption and altered sexual development in aquatic organisms: an invertebrate perspective

Contaminants causing sex-altering, endocrine disrupting-like (ED) effects, or otherwise influencing reproduction, have been of growing concern to humans for more than 50 years. They have also been a perturbing, though less well-studied, phenomenon in marine organisms, following the recognition of tributyltin (TBT)-induced imposex and population extinctions in (neo)gastropods in the 1970s. Whilst ED impacts in mammals and fish are characterized by mimicry or antagonism of endogenous hormones by environmental contaminants (acting through Nuclear Receptors which are present in all metazoans) much less is known regarding pathways to effects in invertebrates. Despite the absence of a defined steroidal/mechanistic component, the extent, severity and widespread nature of ED-like manifestations and altered sexual characteristics observed in marine invertebrates gives rise to comparable concerns, and have been a long-term component of the MBA's research remit. The manifestations seen in sensitive taxa such as molluscs and crustaceans confirm they are valuable indicators of environmental quality, and should be exploited in this capacity whilst we seek to understand the pervasiveness and underlying mechanisms. In so doing, invertebrate indicators address aims of organizations, such as the EEA, OECD, UNEP and WHO, charged with management and monitoring of chemicals and ensuring that adverse effects on humans and the environment are minimized (Bergmanet al., 2013). In view of the recent general declines in marine biodiversity, and the potential contribution of ED-like phenomena, safeguarding against deleterious effects through increased research which links pollutant exposure with reproductive dysfunction among invertebrates, is seen as a high priority.