Association between cadmium and calcium uptake and distribution during the moult cycle of female shore crabs, Carcinus maenas:: an in vivo study

Net influxes into the haemolymph and tissue distribution of Ca-45 and Cd-109 were studied in vivo in female Carcinus maenas at different moult stages. Net influxes of Ca-45 and Cd-109 from water were higher in postmoult (A and B) C maenas than in C-3- and C-4-intermoult crabs and the net influx of calcium was higher in C-3-intermoult crabs than in C-4-intermoult crabs. The net influxes of Ca-45 and Cd-109 increased in postmoult C. maenas with decreasing external calcium concentrations at constant salinity. At all external calcium concentrations a significant correlation existed between 45 Ca and Cd-109 accumulated in the haemolymph of individual animals. In vivo exposure of postmoult C. maenas to external lanthanum decreased the Ca-45 and Cd-109 uptake rates to 30 and 10%, respectively, of the control values. About 30% of injected Cd-109 were found in the midgut gland, 10-20% in the gills and only a few (1-2) percent was lost to the seawater 24h after injection. No major variations in tissue distribution of 109Cd were observed between moult stages in these tissues. Premoult crabs retained more cadmium in the haemolymph 24 h after injection than other moult stages, and postmoult crabs retained more in muscle. Between 20 and 40%, of the injected 45 Ca were excreted to the water, while only a few percent of the injected 41 Ca were found in the soft tissues 24 h after injection. Large m cult stage variations, however, were observed in the tissue distribution of internalised 45 Ca. This study demonstrates that cadmium and calcium uptakes are elevated in postmoule C. maenas. The results indicate that cadmium and calcium in this stage are taken up via Ca2+-channels located in the apical membrane of gill epithelium cells. When internalised, however, cadmium and calcium are metabolised in fundamentally different ways, determined by the chemical properties and biological significance of the two metals. (c) 2004 Elsevier B.V All rights reserved.