Lipofuscin accumulation in tissues of Arctica islandica indicates faster ageing in populations from brackish environments

Environmental factors can affect the rate of ageing and shape the lifespan in marine ectotherms. The mechanisms and the degree of - environmental influence on aging can best be studied in species with wide ranging biogeographic distribution. One of the biomarkers of physiological ageing is the fluorescent age pigment lipofuscin, which accumulates over lifetime in tissues of bivalves. We compared lipofuscin accumulation rate in muscles and respiratory tissues of the extremely long lived bivalve Arctica islandica from five geographically distinct populations (Northern Norway, White Sea, Kiel Bay, German Bight and Iceland). Maximum investigated chronological age across different populations in the present study differed from 40 years in Kiel Bay to 192 years at Iceland. An inverse association between lipofuscin deposition rate and recorded maximum age was observed through inter-population comparisons. In most cases lipofuscin accumulated exponentially over age in a tissue specific manner. The age specific lipofuscin content was significantly higher in respiratory than muscles tissues in all populations. Cellular lipofuscin granule area can be used as indicator of aging across A. islandica populations with the variance in granule accumulation depending on the annual variations of salinity in different marine regions, but not on the habitat specific thermal envelope.