Effects of cadmium on gill Na,K-ATPase activity of the estuarine crab Chasmagnathus granulata (Decapoda, Grapsidae) during postmolt: in vivo and in vitro studies

RODRIGUEZ MORENO P, SCHWARZBAUM PJ, RODRIGUEZ EM

BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY

SPRINGER

Año: 1998 p. 626 - 629

0007-4861

Adult and juvenile crabs of the species Chasmagnathus granulata live on themuddy flats of Samborombón bay, the external sector of the Río de la Plataestuary (Argentina), where they constitute a source of food for several fishspecies of commercial value. As a correlate to the fluctuating salinity of theenvironment, these estuarine crabs proved to be a strong ionic regulatorspecies (Bromberg et al. 1995). This is mainly because of the gill Na,KATPase,whose activity allows a steady-state distribution of ions across thebasolateral membrane to be maintained (Towle 1990).Size growth of crabs implies molting. During this process, the resorption of theold exoskeleton takes place during the premolt stage; whereas the newcuticle is formed below (Passano 1960). During postmolt, on the other hand,the uptake of calcium into the organism is required for carapace calcification(Cameron 1989). Calcium influx is mainly driven by transport systems locatedin the gills. These include primary active transport through calcium ATPasesand/or secondary active transport using the electrochemical gradientgenerated by Na,K-ATPase activity (Roer 1980; Towle and Mangum 1985).In the estuary of Río de la Plata, cadmium was detected above thepermissible levels in 82 % of the water samples analyzed (ComisiónAdministradora del Río de la Plata 1990). This might put crab osmoregulationat risk, since cadmium has been reported to inhibit Na,K-ATPase activity inhomogenates and subcellular fractions from different tissues (Kinne-Saffranet al. 1993; Lijnen et al. 1991). Moreover changes in gill ultrastructure ofcrustaceans occurred during chronic exposure of individuals to sublethalconcentrations of cadmium (Papathanassiou 1985). Thus, this study seeks toevaluate the impact of cadmium on branchial Na,K-ATPase activity frompostmolt crabs. This work represents a first step in a global research on theeffect of cadmium on the molting process of the crab C. granulata.