Activities of Uricase, Xanthine Oxidase, and Xanthine Dehydrogenase in the Hepatopancreas of Aquatic and Terrestrial Crabs

Abstract

To examine the effect of habitat on urate metabolism in crabs, we measured the activities of xanthine oxidase (XOD), xanthine dehydrogenase (XDH), and uricase in the hepatopancreas of two species of aquatic crabs, the blue crab Callinectes sapidus and the stone crab Menippe mercenaria, and two species of land crabs, the blackback land crab Gecarcinus lateralis and the blue land crab Cardisoma guanhumi. Only aquatic crabs showed measurable activities of uricase: 11.5 ± 1.1 nmol urate oxidized per min and per g tissue for C. sapidus (N = 4) and 1.2 ± 0.7 nmol min-1 g-1 (N = 11) for M. mercenaria. These crabs also exhibit a higher XDH activity than XOD activity (approximately 4-5 fold). This is also the case for C. guanhumi but not for G. lateralis which has similar low activities of both enzymes. The possible physiological implications of these results are discussed regarding nitrogenous excretion, blood oxygen transport, and the adaptation of crabs to a terrestrial habitat.