SUBLETHAL EFFECTS OF CADMIUM ON ARM REGENERATION IN THE BURROWING BRITTLESTAR, MICROPHIOPHOLIS-GRACILLIMA

To assess the sublethal effects of sediment-bound cadmium on arm regen eration of Microphiopholis gracillima, a burrowing brittlestar, experi ments were conducted to quantify the tissue and morphology of regenera ting arms, the uptake of cadmium in various tissues and the effect M. gracillima had on the cadmium pools in muddy sediments. Regenerated ar ms of cadmium-exposed M. gracillima are thinner, with proportionally l ess soft and skeletal tissue and a greater number of developing ossicl es than animals held in sediment without cadmium. Microphiopholis grac illima decreased pore water cadmium concentrations in muddy sediments. Uptake of cadmium in tissues dominated by the calcium carbonate endos keleton was proportional to the measured sediment cadmium concentratio n, while concentrations in-whole regenerating arms were more closely r elated to the pore water concentration. Both calcium and cadmium are a ccumulated in the early stages of arm regeneration with an apparent in teraction which interferes with ossicle construction. Sediment-bound c admium has a negative effect on the organism's recovery from sublethal tissue loss and ultimately, its long-term survival.