TOXIC EFFECTS OF CADMIUM ON REPRODUCTION, DEVELOPMENT, AND HATCHING IN THE FRESH-WATER SNAIL LYMNAEA-STAGNALIS FOR WATER-QUALITY MONITORING

The freshwater snail Lymnaea stagnalis was exposed to cadmium concentr ations of 0, 25, 50, 100, 200, and 400 mu g 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 stud ied, Egg production ceased at 400 mu g Cd2+ liter(-1) and hatching was reduced to 0.4% with 200 mu g liter(-1) at 20 degrees C. The study re vealed that embryo development was the most sensitive stage, the main anomalies observed depending on the Cd2+ concentration. At the highest concentration studied (400 mu g liter(-1)) the eggs mere blocked in t he first cleavage stage. At 100 and 200 mu g Cd2+ liter(-1), developme nt of the eggs was halted at various stages of embryogenesis (cleavage , gastrula, veliger, and prehatching) depending on their position in t he egg masses. At concentrations of 25 to 100 mu g Cd2+ liter(-1), dev elopment was slowed down and hatching occurred 5 to 15 days later than in the controls (controls hatched 12 to 13 days after laying). The re sults obtained demonstrate the effects of Cd2+ on reproduction and dev elopment in L. stagnalis and provide information on the targets affect ed (neuroendocrine control of laying or cell multiplication and organo genesis of the embryos). It is thus possible to predict the probabilit y of survival of the species in an environment polluted with cadmium a nd to compare it with the effects of other pollutants in the same or o ther species, (C) 1998 Academic Press.