Life strategies in the long-lived bivalve Arctica islandica on a latitudinal climate gradient-Environmental constraints and evolutionary adaptations

Arctica islandica reaches maximum life span potentials (MLSP) of 405 and 150 years around Iceland and Helgoland, respectively. The combined effects of a low-metabolic lifestyle, low oxidative damage, constant cellular protection and tissue maintenance, appear to slow-down the physiological aging process in A. islandica. Due to low standard metabolic rates and down-regulation of internal pO2, formation rates of reactive oxygen species (ROS) were low in the clam. Proliferation and apoptosis intensities were low, but constant over 140 years of age. Self-induced burrowing and metabolic rate depression (MRD) seem to be key energy-saving and life-prolonging parameters in A. islandica. During shell closure, mantle cavity water pO2 decreased to 0 kPa for longer than 24 h, while anaerobic metabolism was initially detected after 3.5 days of MRD. A ROS-burst was absent in isolated gills of A. islandica following hypoxia-reoxygenation, antioxidant capacities remained equally high under normoxia and MRD. Local impacts of environmental conditions on behavioral and physiological traits in the clams seem to be responsible for different population-specific MLSPs.