Toxic Effects of Cadmium on Reproduction, Development, and Hatching in the Freshwater SnailLymnaea stagnalisfor Water Quality Monitoring

The freshwater snailLymnaea stagnaliswas exposed to cadmium concentrations of 0, 25, 50, 100, 200, and 400 μg liter−1. The influence of this highly toxic metal on various stages of reproduction (number of egg masses, number of eggs, embryo development, and hatching) was studied. Egg production ceased at 400 μg Cd2+liter−1and hatching was reduced to 0.4% with 200 μg liter−1at 20°C. The study revealed that embryo development was the most sensitive stage, the main anomalies observed depending on the Cd2+concentration. At the highest concentration studied (400 μg liter−1) the eggs were blocked in the first cleavage stage. At 100 and 200 μg Cd2+liter−1, development of the eggs was halted at various stages of embryogenesis (cleavage, gastrula, veliger, and prehatching) depending on their position in the egg masses. At concentrations of 25 to 100 μg Cd2+liter−1, development was slowed down and hatching occurred 5 to 15 days later than in the controls (controls hatched 12 to 13 days after laying). The results obtained demonstrate the effects of Cd2+on reproduction and development inL. stagnalisand provide information on the targets affected (neuroendocrine control of laying or cell multiplication and organogenesis of the embryos). It is thus possible to predict the probability of survival of the species in an environment polluted with cadmium and to compare it with the effects of other pollutants in the same or other species.