Hydrothermal Vents as a Possible Natural Pollution Laboratory: Metal Detoxification Mechanisms in Mussels and Fishes from Lucky Strike

Abstract

Deep-sea hydrothermal vent environments are considered highly toxic with high temperatures, sulphide, methane, carbon dioxide and heavy metals. Paradoxically, life at the vents exhibits high productivity and therefore provides a unique way to study the effect of long-term adaptation to environmental stress. The aim of this study was to compare the responses of some biomarkers of metal exposure between two hydrothermal species, the mussel Bathymodiolus azoricus and the chimaera fish Hydrolagus pallidus from Lucky Strike vent field. Results show high metal levels in B. azoricus compared to their coastal counterparts, especially for Ag, Cd, Cu and Zn in the gills. However, metallothionein (MT) levels were surprisingly low taking into account the metal accumulation. H. pallidus also exhibited significantly higher metal concentrations in the gills than the muscle, however with MT levels 2-fold higher in the muscle. Superoxide dismutase (SOD) and catalase (CAT) activities in the mussels were significantly higher in the gills, while glutathione peroxidases (GPx) were present mainly in the mantle, suggesting the two tissues have different antioxidant responses to deal with stress factors. Lipid peroxidation (LPO) was more evident in the gills, indicating that defence mechanisms in this tissue may not be completely effective against metal toxicity. Although the major food source for H. pallidus consists in metal overloaded mussels, no evidences of metal bioamplification were found. Chimaeras may possess other detoxification mechanisms that can be more important than MT.