Cadmium (Cd) is an environmental pollutant and has posed a potential threat for the growth and survival of freshwater crabs. Low-molecular-weight chitosan (LMWC) may promote growth in crab culture. The present study was designed to investigate the Cd-induced oxidative damage and the protective role of LMWC against oxidation caused by Cd 21 in freshwater crab (Sinopotamon yangtsekiense Bott 1967). The results showed that Cd 21 signi¢cantly inhibited the activities of total antioxidant capacity, superoxide dismutase, catalase, glutathione peroxidase and peroxidase, while it increased malondialdehyde levels in the hepatopancreas and the gill. Moreover, Cd 21 at the concentration tested obviously increased the protein carbonyl contents and DNA^protein crosslinks coe⁄cients in the hepatopancreas, gill, heart and muscle tissues of S. yangtsekiense in a dose-dependent manner. In addition, Cd 21 induced a signi¢cant increase in the levels of nitric oxide and inducible nitric oxide synthase in the hepatopancreas, gill and muscle. The results also showed that LMWC plus Cd 21 signi¢cantly improved antioxidant markers. The observations suggested that the severe oxidative damage in multiple crab tissues was one of the important causes of the adverse in£uence of Cd 21 on S. yangtsekiense growth and indicated that LMWC could provide a protective e¡ect against such an injury.

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