Some laboratory studies on freshwater snails and the effect of some plants on their biological control in Beni-Suef governorate

Freshwater snails collected from ditch like ponds near the River Nile in Beni-Suef Governorate during three climatically differed periods. Lymnaea cailliaudi, Biomphalaria alexandarina, Bulinus truncatus, Lanistes carinatus, Cleopatra bulimoids,Physa acuta, Viviparus viviparus, Melania tuberclata and Bivalves species were included. The total number of collected snails in December 2008, March 2009 and July 2009 were 1321, 1370 and 1211 respectively, with larger number in March than in July or December due to optimal climatic conditions in Marsh for most of collected snails. The recorded survival longevity in the laboratory was more than 90 days for Lymnaea cailliaudi, two months for Lanistes carinatus, while in Melania tuberclata, was about three weeks but only two to three days for Bivalves. Cercariae shedding observed from Lymnaea, Lanistes and Biomphalaria species beside stylet cecariae from Lymnaea and Lanistes snails, also rediae and sporocysts were found in crushed snails in all periods of collections with little difference between these periods, about 14% of crushed Lymnaea were containing rediae. Aquatic insects and their larvae were found especially water bug Sphaerodema sp. found predating snails or their eggs, also the mature insect still alive in the breeding container all over the period of the experiment more than three months. Culex larvae attacked egg masses of the snails, estacosa predated the snails while Telapia nilotica fishes showed low affinity to predate such snails. The oleo-gum resin Myrrh (Commiphora molmol) in the concentration of 0. 5gm/1 litre water killed 90 % of the exposed snails after 72 hours.