The first frost was a couple of weeks ago, and the flora and fauna of the Arboretum are preparing for the approaching winter. Some of the Arboretum’s animals hibernate, like chipmunks and bats, some enter states of dormancy – birds have “torpor,” a short-term reduction in metabolic activity – and some tough out the cold. Have you ever wondered how the Arboretum’s snails and slugs respond to extreme weather?
Snails and slugs are gastropods. They are slow-moving and demonstrate pronounced relaxation in extreme weather conditions, hot or cold. In the summer, gastropods spend the hottest hours of the day in a resting state called “aestivation” (see https://www.molluscs.at/gastropoda/terrestrial.html?/gastropoda/dormancy.html). During aestivation, most land snails seal the opening of their shells with a mucus membrane called an “epiphragm.” Door snails (Clausiliidae) have a unique closure mechanism that uses a small calcareous plate called a “clausilium” to close the shell when they recede. Snails that aestivate outside often have lighter colored shells, which minimize evaporation. Slugs, on the other hand, do not have protective shells and aestivate underground in burrows.
Snails use similar techniques of enhanced relaxation to overwinter. They cannot easily withstand extreme cold, so many species hibernate. They bury themselves in soil and litter, or find shelter in rotting wood, and seal their shells with an epiphragm. Some species also lower their water content to prevent freezing and produce glucose, which can minimize damage from freezing. For the extent of the winter, snails enter a stage of dormancy and are able to survive extremely cold temperatures. Hibernation allows snails to survive up to a couple of years, while slugs live shorter lives. They lay eggs in autumn and die as temperatures drop.
From a materials science perspective, epiphragm is fascinating. Scientists have struggled to create reversible superglues (glue that can be later removed without damage). Epiphragm is incredibly strong and entirely reversible. It has inspired modern adhesion methods, helping scientists come closer to creating reversible superglues (see https://pmc.ncbi.nlm.nih.gov/articles/PMC11816236/#sec1-animals-15-00348).
- Dexter Pakula ’26, for the Cole Student Naturalists
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