X-ray microanalysis of freeze-dried ultrathin frozen sections of a regulating epithelium from the snail Otala

Abstract

MANY epithelial cells are known to regulate the flow of water and ions across the epithelium. This has been observed in various animals¹ and is probably an essential feature of all living organisms. Hibernating Otala lactea (Mollusca, Gastropoda, Pulmonata) can survive long periods of drought without access to water by regulating the evaporative water loss from the mantle epithelium². Machin² has shown that these snails are as efficient as insects at controlling water loss when they are hibernating, yet when they are active and crawling they lose water at the same rate as does a free water surface. To achieve this the animals produce an osmotic gradient across the mantle epithelial cells of approximately 4.5 Osm kg⁻¹ from the cell base to the apical plasma membrane². X-ray microanalysis of freeze-dried frozen sections has shown that the levels of silicon, chlorine, potassium, iron and zinc are significantly greater in hibernating (regulating) mantle tissue than in tissues taken from normal actively crawling snails, and a gradient can be observed within these cells.