Much information is available on the accumulation and effects of toxic substances in aquatic organisms (Malins & Ostrander 1991). Fewer studies, however, have examined toxic mechanisms in marine biosystems. Present experiments provide information on the mechanism by which cadmium penetrates into tissues of the small marine organism known as the brine shrimp. Brine shrimp are of major importance in the aquaculture industry and they have been proposed as a uniform world-wide test system for toxicity of chemical substances (Vanhaeke et al. 1981) and for studies in developmental toxicology (Sleet & Brendel 1985).