The acclimation and adaptation to cadmium (Cd) by the aquatic oligochaete LIMNODRILUS HOFFMEISTERI was investigated for its role in controlling bioavailability and toxicity of Cd to the predatory grass shrimp PALAEMONETES PUGIO. Acclimation to Cd and its effect on Cd trophic transfer were investigated by varying the concentration and duration to which nonresistant oligochaetes were exposed to Cd and determining the relationship between oligochaete subcellular Cd distributions and Cd bioavailability to shrimp. The consequences of adaptation to Cd on Cd trophic transfer was investigated by collecting oligochaetes along a Cd-contamination gradient in a metal-polluted (Cd, Ni and Co) cove on the Hudson River (Foundry Cove) and determining differences in Cd resistance, subcellular Cd distributions, and Cd bioavailability to shrimp. The toxicity of Cd sequestered within oligochaetes was studied by investigating alterations in prey capture and induction of Cd-binding proteins in shrimp fed Cd-contaminated oligochaetes.

Acclimation to Cd resulted in an increase in the proportion of Cd bound to the cytosol of oligochaetes (possibly due to the production of metallothionein-like proteins) and in the proportion of Cd biologically available to shrimp; Cd bound to cytosol was completely absorbed by shrimp. Oligochaetes chronically exposed to Cd evolved Cd resistance and produced Cd-rich granules. Cd sequestered in granules was biologically unavailable due to the insolubility of these concretions.

Shrimp fed Cd-contaminated prey items (LIMNODRILUS HOFFMEISTERI OR ARTEMIA SALINA) exhibited significant and obvious reductions in their ability to effectively capture live prey (A. SALINA). Just as with oligochaetes exposed to Cd via solution, the percentage of Cd bound in the cytosol of shrimp increased with increased Cd exposure; induction of Cd-binding proteins (metallothioneins) was directly responsible for this increase in cytosol bound Cd. Additionally, prey capture success was inversely related to (1) the percentage and amount of Cd bound in the cytosol of shrimp, (2) shrimp Cd body burdens, and (3) the amount of Cd bound to the high molecular weight protein fraction of shrimp cytosol (i.e., Cd not detoxified via metallothioneins).

This study has integrated physiological induction of metal detoxification systems, development of metal resistance, and effects on metal trophic transfer and toxicity to predators. This scheme represents the development of a physiological approach to understanding the impacts of metals on aquatic environments, and, together with previous work, describes a model linking molecular aspects of metal resistance in prey to direct consequences to predators, and by extension to the ecosystem as a whole. This model extends beyond Cd, oligochaetes and grass shrimp to include other predator/prey relationships in which other toxic metals (i.e., Cu, Zn, Co, Ni, Cr, Ag and Hg) are sequestered and detoxified by similar mechanisms.