Tissue accumulation and the effects of long-term dietary copper contamination on osmoregulation in the mudflat fiddler crab Minuca rapax (Crustacea, Ocypodidae)

Abstract

We examined copper accumulation in the hemolymph, gills and hepatopancreas, and hemolymph osmolality, Na+ and Cl− concentrations, together with gill Na+/ K+-ATPase and carbonic anhydrase activities, after dietary copper delivery (0, 100 or 500 Cu μg g−1) for 12 days in a fiddler crab, Minuca rapax. In contaminated crabs, copper concentration decreased in the hemolymph and hepatopancreas, but increased in the gills. Hemolymph osmolality and gill Na+/ K+-ATPase activity increased while hemolymph [ Na+] and [ Cl−] and gill carbonic anhydrase activity decreased. Excretion likely accounts for the decreased hemolymph and hepatopancreas copper titers. Dietary copper clearly affected osmoregulatory ability and hemolymph Na+ and Cl− regulation in M. rapax. Gill copper accumulation decreased carbonic anhydrase activity, suggesting that dietary copper affects acid–base balance. Elevated gill Na+/ K+-ATPase activity appears to compensate for the ion-regulatory disturbance. These effects of dietary copper illustrate likely impacts on semi-terrestrial species that feed on metal-contaminated sediments.