Cell turnover in tissues of the long-lived ocean quahog Arctica islandica and the short-lived scallop Aequipecten opercularis
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Cell proliferation and apoptosis were investigated in tissues of two bivalve species, Arctica islandica from the German Bight (age of bivalves: 33–98 years) and Iceland (7–148 years) and Aequipecten opercularis from the English Channel (2–4 years). High proliferation rates (10% nuclei dividing) and apoptosis in tissues of A. opercularis were in line with high-energy throughput and reduced investment into antioxidant defence mechanisms in the scallop. In contrast, cell turnover was slow (<1% nuclei dividing) in A. islandica and similar in mantle, gill and adductor muscle between young and old individuals. In the heart, cell turnover rates decreased with age, which indicates less-efficient removal of damaged cells in ageing A. islandica. Cell turnover rates, mass specific respiration and antioxidant enzyme activities were similar in German Bight and Iceland ocean quahog. Variable maximum life expectancies in geographically separated A. islandica populations are determined by extrinsic factors rather than by fundamental physiological differences.