INFLUENCE OF AN INSECTICIDE, K-OTHRINE, ON THE REPRODUCTION AND MORTALITY OF THE POND SNAIL (LYMNAEA-STAGNALIS L)

The toxicity of K-Othrine, an insecticide containing a synthetic pyret hroid derivative (deltamethrin) as an active ingredient, was studied o n the pond snail, Lymnaea stagnalis L. This insecticide is used for th e control of mosquitoes around Lake Balaton, Hungary. The adult snails were kept in a variety of concentrations (1, 10, and 100 mug/L) of K- Othrine solution (1st, 4th, and 7th weeks) as well as in clean tap wat er (2-3rd and 5-6th weeks) over a 7-week period. The pesticide treated snails deposited significantly more eggs than those in the control, b ut the hatched snails showed a survival rate significantly lower than the control values. The snails that were hatched in the insecticide so lution and survived were kept in clean water (2nd generation, group 1) . By the end of the experiment (18th week) the survival rate of the sn ails was 30% lower than that of the snails hatched and kept in clean w ater (2nd generation; control, group IV). The number of deposited eggs was 45% less than in the control. The snails hatched in insecticide-s olution and treated with K-Othrine similarly to their parents from the 1st till the 7th week (2nd generation, group II) showed a survival ra te 35% lower than that of the control. The snails reached maturity wit h a significant delay, and 73-94% fewer eggs were deposited than in th e control. The survival rate of the snails hatched in clean water and kept in K-Othrine solution similarly to group II (2nd generation, grou p III) was 15-20% lower, and the number of deposited eggs were 73-85% fewer than in the control. The data on survival and reproduction suppo rt the hypothesis that the considerable toxic aftereffect of K-Othrine is of a cumulative nature.