Age‐ and size‐related oxidative stress in marine mollusks

Abstract

According to one of the most well developed theories of aging, the “Free Radicals” theory, production of free oxygen radicals causes oxidative damage in aerobically respiring animals, which in turn is associated with aging and death. Products of oxidative damage accumulate in non-proliferating tissues of most of the traditional objects of aging studies (mammals, insects, nematodes). There is a vast number of species, which grow during the whole life and therefore, many physiological processes, including metabolic rate, may depend on both age and size in such organisms. The main objective of our study was to distinguish between effects of age and size on oxidative damage and antioxidant defense in two species of marine bivalve mollusks. We determined the levels of lipofuscin and protein carbonyls as markers of lipid and protein oxidation, respectively, and the activity of antioxidant enzymes catalase and superoxide dismutase in gill and muscle tissues of mollusks. Lipofuscin progressively accumulated in tissues with increasing age of the animals and decreased in intensively growing specimens. Protein carbonyl levels did not show age- or size-related changes. Activity of enzymes tended to decrease with age of mollusks and did not depend of their size. Our data show that signs of aging in infinitely growing species can interfere with growth and can be masked by size effects, which must be taken into account.