Sublethal effects of cadmium on arm regeneration in the burrowing brittlestar, Microphiopholis gracillima.

: To assess the sublethal effects of sediment-bound cadmium on arm regeneration of Microphiopholis gracillima, a burrowing brittlestar, experiments were conducted to quantify the tissue and morphology of regenerating arms, the uptake of cadmium in various tissues and the effect M. gracillima had on the cadmium pools in muddy sediments. Regenerated arms of cadmium-exposed M. gracillima are thinner, with proportionally less soft and skeletal tissue and a greater number of developing ossicles than animals held in sediment without cadmium. Microphiopholis gracillima decreased pore water cadmium concentrations in muddy sediments. Uptake of cadmium in tissues dominated by the calcium carbonate endoskeleton was proportional to the measured sediment cadmium concentration, while concentrations in whole regenerating arms were more closely related to the pore water concentration. Both calcium and cadmium are accumulated in the early stages of arm regeneration with an apparent interaction which interferes with ossicle construction. Sediment-bound cadmium has a negative effect on the organism's recovery from sublethal tissue loss and, ultimately, its long-term survival.