Factors Affecting the Predation of Marisa cornuarietis on Bulinus (B.) truncatus, Biomphalaria alexandrina and Lymnaea caillaudi

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Abstract
The rate of which adult individuals of Marisa cornuarietis prey on adult and juvenile Bulinus truncatus and Lymnaea caillaudi increases with temperature up to about 30C, then decreases slightly. This predatory activity normally decreases in the presence of abundant vegetable material, however adult Marisa, while preying on Bulinus and Lymnaea, become habitual predators, regardless of the presence of vegetable food. The rate of predation directly proportional to the ratio of predators to prey, and is little affected by population densities. Adult and juvenile Marisa are capable of preying freely on newly hatched individuals of Bulinus, Biomphalaria alexandrina and Lvmnara and ingesting them whole; with larger specimens they attack only the soft parts. Adult Marisa consume egg-masses of the 3 vector snails more voraciously than do newly hatched and juvenile Marisa Marisa of all ages considerably reduce Bulinus, Biomphalaria and Lymnaea population.