AGE-RELATED CELLULAR AND PHYSIOLOGICAL REACTIONS TO HYPOXIA AND HYPERTHERMIA IN MARINE MUSSELS

Marine mussels Mytilus edulis (L.) from 3 different age/size groups we re exposed for 24 h to combined hypoxia and hyperthermia (28 +/- 1 deg rees C) and subsequently reimmersed in seawater at 10 +/- 1 degrees C. Exposure to the physical stressor induced lysosomal destabilisation a nd enlargement in the digestive cells of mussels of all ages. Recovery of lysosomal integrity was demonstrated after 24 h in seawater by the youngest mussels (2-4 yr) only. Levels of unsaturated neutral Lipids increased in all mussels following exposure and was associated with en larged lysosomes. No consistent pattern or significant change was obse rved in lipid levels in mussels of any age during the recovery period. Levels of Lipofuscin (stress pigment) in mussels exposed to hypoxia a nd hyperthermia and in those subsequently reimmersed in seawater did n ot follow any consistent pattern, but were generally much higher in th e youngest mussels than in the older age groups. Recovery of metabolic rates to control levels was observed 12 h after reimmersion in seawat er in the youngest mussels only. Metabolic rates of the 6-8 and greate r than or equal to 10 yr mussels remained elevated relative to the con trols after this time. These findings indicate that the stress reactio n is independent of age but that the potential for recovery of lysosom al integrity and metabolic rate is age-related.