Water regulation in aestivating snails

Summary Aestivating snails form abundant lamellate vesicles in the cells of the mantle collar, an epithelium known to regulate the rate at which water is lost from its surface. Since lamellate vesicles are much reduced in hydrated mantle tissue of recently stimulated animals it is tentatively concluded that the vesicles, and their contents, form a barrier to water movement within these cells. X-ray microanalysis of unfixed thin sections shows that there is a concentration gradient of ions within these cells in aestivating animals which is not present in stimulated snails.Financial support from the National Research Council of Canada and the Atkinson Foundation. Toronto, is gratefully acknowledged. The work was performed during the sabbatical leave of one of us, using the facilities of the Department of Zoology and the Faculty of Medicine Electron Microscope Unit (supported, in part, by grant M.A. 4038 of the MRC of Canada), University of Toronto