To determine the effect of nematode infection on the response of snails to selected toxins, we infected Helix aspersa with 0-, 0.25-, 1-, or 4-fold the recommended field dose of a commercial nematode application for agricultural use. In the first experiment, the snails also were exposed to cadmium via food and soil at concentrations of 0, 30, 60, 120, or 240 mg/kg in a full-factorial design. In the second experiment, snails were infected with nematodes and also fed either Bt (expressing Bacillus thuringiensis toxin) maize or non-Bt maize. The snails were weighed at the beginning and end (after four weeks) of the experiments, and mortality was checked daily. Neither exposure of snails to nematodes nor exposure of snails to cadmium or Bt toxin affected the survival rates of snails. The number of dead snails was highest for combinations of nematode treatments with cadmium concentrations of 120 and 240 mg/kg. In both experiments (Bt and cadmium), the growth rate decreased with increasing nematode dose. The Bt maize was not harmful to the snails in the absence of nematodes, but infected snails grew faster when fed non-Bt maize. The growth rate of snails exposed to cadmium decreased with exposure to increasing Cd concentrations and differed significantly between the no-nematode treatment and the treatments with nematode doses of one- and fourfold the recommended field dose. Snails treated with the highest dose of nematodes accumulated the highest cadmium concentrations.

At five sites located along a metal-pollution gradient in southern Poland, we collected, during the spring and summer of 2000, more than 1,200 individuals of the ground beetle (Pterostichus oblongopunctatus) to examine the relationship between pollution level and body mass. Animals from one additional sampling in May 2001 were used to measure body caloric value to verify whether metal pollution has an effect on the energy content of the body. The study sites were located in an area with a history of zinc and lead mining and smelting dating back to medieval times. Metal concentrations in the humus layer ranged from 200 to 9,600 mg/kg of zinc, 120 to 1,600 mg/kg of lead, and 3 to 82 mg/kg of cadmium. We found a significant increase in body mass with increasing pollution level. The beetles from all sites collected near the end of the season were lighter. However, no statistically significant trend in body caloric value was detected. We suggest that the high metal tolerance of the species, combined with altered interspecies competition at the polluted sites, is responsible for the positive correlation between soil metal concentration and body mass.