RESUMEN
The effect of low concentrations of different synthetic and natural mollusciciding agents may introduce to fresh water environment on reproduction and biochemical aspects of Biomphalana alexandrina was studied. Different mollusciciding agents [copper sulphate, ayluscide, Uccmaluscide, Agave filifera and A. attenuate] inhibited egg production, induced marked increased the percent of abnormal laid eggs and induced marked reduction in their hatchability. The maximal reductions in egg hatchability resulted with Bayluscide [0.0%] and Uccmaluscide [18%], A. filifera [21%] and A. attenuata [15%]. All the antimolluscal materials caused a successful killing effect against miracidia and cercariae of Schistosoma mansoni. CuSo4, Bayluscide and Uccmaluscide killed 40% of the exposed miracidia and 50% of cercariae after an hour exposure. The plants sublethal concentration killed 100% of cercariae and miracidia after 6 hours oexposure. Water leaving behaviour among the exposed snails was noticed especially during the first three weeks, showing maximal percentage [60%] after one week of exposure to Bayluscide. A general decrease in the activity of alkaline phosphatase [ALP] especially with Bayluscide [48.4%] and in acetylecholine esterase activity in the haemolymph especially on applying plant molluscicide A. filifera [50.8%] was noticed. Transaminases showed marked elevations in activities during the three weeks, then began to drop [ASAT: 6 1.5%, with Bayluscide and ALAT: 50.8% with Uccmaluscide]. The results reflect the effect of the metabolic disorders on life, egg laying, egg hatchability, hepatic cells damages, lack of smooth trans-mission at nerve junction, loss of muscular coordination and convulsions, then snails' death