Arsenic occurrence and speciation in Cyclope neritea, a gastropod inhabiting the arsenic-rich marine shallow-water hydrothermal system off Milos Island, Greece

Abstract

Around Milos Island marine shallow-water hydrothermal activity can be found and in Paleochori Bay, where high arsenic concentrations were reported for the hydrothermal fluids. There the gastropod Cyclope neritea was present at high densities despite the extreme conditions associated with hydrothermal venting, feeding on white microbial mats. Surprisingly, C. neritea collected from the hydrothermal vent area accumulated comparatively less arsenic in its tissues than specimens of the same species collected from an area not affected by hydrothermal activity. Inorganic arsenic was found at high percentages with respect to the sum of arsenic species both in the gut and muscle of C. neritea and the amount of arsenobetaine (AB) was less than in specimens collected at an area away from hydrothermal activity. Trimethylarsoniopropionate (TMAP) was found at relatively high percentages in C. neritea and in the surrounding environment (sediment and plankton) in Paleochori Bay. Tetramethylarsonium ion (TETRA) was found at high percentages in the gut and muscle of C. neritea. It was most likely biosynthesized in the gastropod gut, and accumulated in the muscle, because it was not found in any other compartment studied. Based on these observations we conclude that C. neritea is arsenic tolerant. The data suggests that arsenic species distribution is strongly influenced by arsenic species exposure and/or different detoxifying mechanisms, although the exact metabolic pathways could not be completely resolved.