INTERSPECIFIC COMPARISONS OF RELATIVE ASSIMILATION EFFICIENCIES FOR ZINC AND CADMIUM IN AN ECOLOGICAL SERIES OF TALITRID AMPHIPODS (CRUSTACEA)

A dual-labelling radioisotope technique has enabled the relative assim ilation efficiencies of an essential (Zn) and a non-essential trace me tal (Cd) to be determined in an ecological series of talitrid amphipod s from low-shore to fully terrestrial habitats. All species exhibited high assimilation efficiencies for zinc and cadmium (within the range 66.7-96.4%). Interspecific differences in assimilation rates showed no trend with increasing terrestriality of the habitat. Elevated dietary zinc concentrations failed to enhance zinc assimilation efficiency. I ncorporation of antibiotics into the diet to eliminate gut microflora did not affect zinc assimilation efficiencies. The implications of hav ing high trace-metal assimilation efficiencies are discussed in terms of land invasion by talitrids.