Oxidative-stress: comparison of species specific and tissue specific effects in the marine bivalves Mytilus edulis (L.) and Dosinia lupinus (L.)

This study describes a novel approach to the objective of identifying a suitable biomarker of oxidative-stress in marine animals and evaluates an established assay under controlled experimental conditions in vivo and in vitro. Live animals and tissue homogenates of the euryoxic blue mussel Mytilus edulis (L.), and the stenoxic smooth artemis Dosinia lupinus (L.), were exposed to oxidative-stress generated using a 60Co γ-radiation source. In live organisms, mortality-rates were significantly different between species. M. edulis showed zero mortality and D. lupinus 30% mortality over 18 h. Protein-carbonyl (PCO) content was determined by colourimetric assay (total protein-carbonyl) or immunodetection (for individual proteins) in four tissue types: digestive gland, mantle, adductor muscle and foot. In tissue homogenates, digestive gland and adductor muscle of both species showed significant increases (greater for D. lupinus) in PCO content following irradiation in vitro. All tissues from live animals (with the exception of M. edulis mantle and adductor muscle of D. lupinus which died under irradiation) showed significantly different levels of PCOs following irradiation; D. lupinus PCO levels were increased whilst in M. edulis PCO content decreased. In D. lupinus which died during irradiation, PCO content was greater than in those D. lupinus which survived, particularly in the adductor muscle, the former were inceased by 74% above controls. The findings support the hypothesis that species-specific adaptations to euryoxic and stenoxic environments, and metabolic requirements of different tissues, should result in differing ROS defences.