The ocean quahog A. islandica is among the longest-lived and slowest growing of marine bivalves with maximum ages > 300 years (e.g. Schöne et al. 2003, 2004). The animals exhibit a unique behaviour of self-induced metabolic reduction, by seemingly at random burrowing under to anoxic sediment layers (Taylor 1976). The time burrowed represents a period of deliberate metabolic reduction with heart rates suppressed to 10% of normoxic levels (Taylor 1976). Living at a much slower pace increases individual life span (Yoon et al. 2002) and therewith the chances to participate in yet more reproduction events. However, in mammals, chronic intermittent hypoxia increases oxidative stress (Peng & Prabhakar 2003) and, both, hypoxia and oxidative stress cause functional and biochemical changes (Chi & Karliner 2004). We conjecture that chronic anoxic/oxic exposure fosters the extreme stress resistance in A. islandica. The Ocean quahog is the only animal known to deliberately induce a torpor-like state that does not serve to escape adverse conditions (like hibernation in snails and frogs) but, presumably, to prolong individual life span. This behaviour speaks for a unique level of stress competence (Diaz & Rosenberg 1995, Storey 1996, Abele 2002), presumably based on unique physiological and genetical features.Investigations of quality and plasticity of the hypoxia response and of the biochemical cue for surfacing in young and aged individuals from different populations with distinct maximum life span (Baltic, White Sea, Mid Atlantic) will provide insight into physiological and genetic mechanisms of the extraordinary stress hardiness in Arctica islandica.