Consumption of Biomphalaria glabrata egg masses and juveniles by the ampullariid snails Pila ovata, Lanistes carinatus and Marisa cornuarietis.

Lanistes carinatus and Pila ovata from Kenya and Marisa cornuarietis from the Dominican Republic were examined for their ability to consume egg masses and juveniles of Biomphalaria glabrata (M line strain) under laboratory conditions. Adults of all three ampullariid species consumed all egg masses presented to them over a five day period of observation. Juvenile P. ovata consumed significantly more egg masses than juveniles of M. cornuarietis or L. carinatus. Both adult and juvenile ampullariids generally ate more egg masses when maintained under a temperature regime (25-32 degrees C) approximating conditions in coastal Kenya than at 13-25 degrees C which approximates the temperature regime near Nairobi, Kenya. Egg masses attached to floating 'refugia' were not attacked, apparently reflecting the difficulty experienced by ampullariids in reaching free-floating objects. Adults of each ampullariid species ate approximately 25% of all lariids in reaching free-floating objects. Adults of each ampullariid species ate approximately 25% of all 1.5 +/- 0.5 mm B. glabrata juvenile snails presented to them. P. ovata adults consumed significantly more 3.0 +/- 0.5 mm juveniles than adults of the other two species. B. glabrata egg masses and juveniles were consumed even though lettuce was continually present in experimental aquaria. Implications of these results for biological control studies in East Africa are discussed.