Mechanisms of maternal transfer of organochlorine contaminants and mercury in the common thresher shark (Alopias vulpinus)

A putative mechanism for maternal transfer of organic contaminants and total mercury was empirically demonstrated in a near-term pregnant female common thresher shark (Alopias vulpinus). Contaminants were measured in the liver and muscle tissue of the mother and her four embryos, as well as the embryos' stomach contents. Concentrations of organic contaminants and mercury were found to be lower in the embryos' livers than in the mother's and were clearly measurable in the embryo stomach contents, which consisted of consumed ovulated eggs. Presence of high concentrations of organic contaminants and mercury in embryos, prior to any exogenous exposure, provides clear evidence of maternal offloading in this species. In addition, the detection of these chemicals in the yolky stomach contents provides a mechanism by which oophagous elasmobranch females offload contaminants onto their young.