Uptake and elimination of arsenobetaine by the mussel Mytilus edulis is related to salinity

The high concentrations of the naturally occurring arsenic compound arsenobetaine in marine animals, in comparison with freshwater animals, has led to the suggestion that salinity is a factor in its accumulation. In separate experiments, we investigated the uptake and elimination of arsenobetaine by the mussel Mytilus edulis when maintained under three salinity regimes (32, 24, and 16 practical salinity units). Both uptake and elimination of arsenobetaine depended on the salinity of the water in a manner leading to higher concentrations at the higher salinity. The data are consistent with a proposed role of arsenobetaine as an adventitiously acquired osmolyte, and readily explain field data for freshwater and marine animals.