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Abstract

Two survival strategies, namely diapause and anhydrobiosis, are exhibited by Biomphalaria glabrata from seasonally drying habitats in the humid eastern coastal areas of N. E. Brazil. Diapause is a syndrome induced by environmental stimuli of predictive value, which enables the snail to avoid seasonal habitat deterioration. It is characterized by a sequence of events, specific to the juvenile phase, which includes lamellae formation at the shell aperture and emigration from the water followed by dormancy, and occurs under favourable conditions. Anhydrobiosis is a state of prolonged quiescence directly elicited by habitat desiccation. It may occur at any life-stage and does not involve lamellae formation or emigration from the water. Diapausing snails are better able to survive out of the water than anhydrobiont snails. The former tend to persist in a dormant state, whereas the latter quickly return to full activity when favourable conditions are restored. The diapause phenomenon by polymorphic B. glabrata has to be accounted for when designing snail control measures in endemic areas of N. E. Brazil.