ABSTRACT
In the present study when the egg masses of Lymnaea stagnalis showing different developmental stages were introduced with the sub lethal concentrations of baygon and nuvan from cleavage to before hatching stages exhibited the development arrest in most of the egg capsules due to deviation in protein fractions in the corresponding development stages in comparison to control groups resulted into high percentage of mortality and low percentage of hatchability in treated groups. Another potent cause of low percentage of hatchability of young snails from their corresponding egg capsules was the phenomenon of polyembryony in nuvan treated egg masses which showed the high rate of mortality due to the lack of metabolites for their progressive development in comparison to control groups. Teratogenesis and deformities in larval stages were also observed in most of the egg capsules which could be correlated with the depletion of most of the protein fractions in the present investigation.