A secreted mucus membrane across the opening of the shells of some land snails protects them from drying out by reducing evaporation.

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"And certain land snails, particularly desert dwellers, seal themselves inside their shells to avoid desiccation in dry conditions, secreting a special membrane across their shells' opening that reduces evaporation; they can remain encased for years if need be until rain returns." (Shuker 2001:105)

Book
The Hidden Powers of Animals: Uncovering the Secrets of NatureDecember 9, 2019
Dr. Karl P. N. Shuker

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