Estivation of Biomphalaria Glabrata (Basommatophora: Planorbidae)

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Abstract
Summary Diapause and estivation were studied in an albino strain of Biomphalaria glabrata. A group of small lamellate B. glabrata showed a persistent tendency, for an average duration of 29 days, to climb out of the water. These snails subsequently produced 36% lamellate offspring, 64% of which showed a spontaneous tendency to climb out of the water. Results suggested that genetic factors influenced the morphologic and physiologic changes that adapted some small B. glabrata for diapause and prolonged estivation. Lamellate snails survived 10 months out of water, and immature Schistosoma mansoni survived in snails 7 months out of water. S. mansoni larvae remained dormant in snails during estivation. In snails remaining in water after exposures to both S. mansoni and Angiostrongylus cantonensis, both infections developed. A. cantonensis developed to third-stage larvae in estivating snails. Estivation provides B. glabrata a survival mechanism against both drought and chemical molluscicides.