Antioxidant defense mechanisms against metal stressors in the commensal polychaete Branchipolynoe seepensis and the host mussel Bathymodiolus azoricus from the Mid-Atlantic-Ridge (MAR)

Trabajo presentado en el 14th Deep-Sea Biology Symposium, celebrado en Aveiro del 31 de agosto al 4 de septiembre de 2015.Hydrothermal vent biology has been studied in an attempt to understand the mechanisms involved in vent organisms that permit their survival and reproduction in extreme conditions. Symbiosis is very important for the subsistence of these deep-sea organisms. The scale-worm Branchipolymoe seepensis lives in the palleal cavity of the mussel vent Bathymodiolus azoricus, the dominant species in the MAR. Polychaetes are known to absorb particles in excess deposited in mussel gills and at the same time get protection. The aim of this study was to understand the metal accumulation in this symbiosis relationship. Mussels B. azoricus were collected from two sites from Lucky Strike Hydrothermal vent (1700m), Montségur-MS and Eiffel Tower-ET and from Rainbow-Rb hydrothermal vent (2300m) where B. seepensis is present. To compare the interaction between both species, mussels were also collected from Menez Gwen hydrothermal vent (MG2, MG3 and MG4) (850m) where polychaetes are not present. Induction of metallothionein (MT) and lipid peroxidation (LPO) levels were higher in polychaetes from Rb and MS vent sites, while in mussels were higher in the gills followed by the digestive gland and mantle in all vent fields. Enzymatic activities (CAT and GST) showed that mussels had higher CAT activity in digestive gland, followed by gills and mantle, while GST levels were higher in gills. In polychaetes , both CAT and GST activities were higher in ET. Metal concentrations (Ag, Cd, Co, Cu, Fe, Mn and Zn) in the cellular and subcellular fractions determined in mussels tissues and polychaetes whole body by ICP-OES suggest intra-and inter-variation of fluid chemistry between hydrothermal vent sites. The subcellular metal partitioning in polychaetes was higher in insoluble and soluble (thermolabile and heat-stable) fractions from ET, MS and Rb, respectively. In mussel tissues, me tal partitioning was higher in gills and digestive gland. Overall, the data suggest that the presence of the scale-worm is an adaptation to the elevated metal concentrations present in vent sites.N