Is metabolic rate depression (MRD) a life prolonging strategy in long-lived Arctica islandica on a latitudinal climate gradient? Environmental constraints and evolutionary adaptation in the Ocean quahog

北极滩(Arctica Island Andica)是一种北极区海洋泥蚌，分布广泛，分布于不同气候条件的栖息地。它也是所有双壳类和软体动物物种中寿命最长的，动物&gt；100岁在许多种群中很常见，据报道最长寿命为374岁(冰岛种群)。然而，还没有报道所有人口都有这种可敬的年龄。根据珀尔(1928)和哈曼(1956)的自由基存活率理论，我们假设随机发作的自我诱导的代谢率抑制(MRD)会降低活性氧的生成率。这可能是海洋中的一种节能和延长寿命的策略。此外，我们假设寒冷的气候将有利于MRD行为，并与温带种群相比，提高预期寿命。在此，我们建议以年龄相关的方式研究来自不同气温制度(冰岛和北海)的两个岛状姬鼠种群的MRD行为。我们将从能量代谢、抗氧化能力、氧化应激指标和脂褐素积累方面比较两个群体中不同年龄个体的有丝分裂后神经元和增殖组织(鳃、外套膜、内收肌)。生理年龄和应激标记将与两个群体的MRD频率和持续时间相关。此外，我们建议研究在自身诱导的低氧/缺氧暴露过程中，NO信号参与MRD的过程。

The ocean quahog Arctica islandica is an arctic boreal marine mud clam with a wide ranging distribution on the Northern hemisphere, spanning habitats with different climate regimes. It is also the longest-lived of all bivalve and molluscan species, animals >100 yrs are common in many populations, and reported maximum live span is 374 yrs (Iceland population). However, such venerable age has not yet been reported for all populations. Based on the Free Radical-Rate of Living theory by Pearl (1928) and Harman (1956) we assume that random bouts of self-induced metabolic rate depression (MRD) will lower generation rates of reactive oxygen species. This may be an energy saving and life prolonging strategy in the ocean quahog. Further, we assume that cold climate will favour MRD behaviour and raise life expectancy in cold-boreal compared to temperate populations.Here we propose to study MRD behaviour in two A. islandica populations from different temperature regimes (Iceland and North Sea) in an age dependent manner. We will compare postmitotic neuronal and proliferating tissues (gill, mantle, adductor muscle) of differently aged individuals from the two populations with respect to energy metabolism, antioxidant capacities, oxidative stress indicators and lipofuscin accumulation. Physiological age and stress markers will be related to MRD frequency and duration in both populations. Moreover, we propose to investigate the involvement of an NO signal in MRD during self-induced hypoxic/anoxic exposure of the quahog.