Snails come out when it rains because they need very high humidity conditions to survive. The shell protects them from predators and helps them retain moisture in their bodies. These animals flee from extreme temperatures. When the weather is very dry, they bury themselves, even up to two meters deep, or hide under rocks or leaves, in sheltered areas near rivers or puddles, always in places where they feel protected from lack of water. This same behavior is carried out during the winter.
Snails move on a muscular structure called a foot, which is full of mucous glands that secrete what we know as slime. This mucus is what allows them to move. The less dry the substrate through which they move, the easier it is for them to move. If there is little humidity, the mucosa dries up and there comes a time when they cannot move and that can cause their death. This drought that we are experiencing in Spain, for example, affects them a lot. In fact, land snails are among the animals most affected by it.
When it rains they can move more easily, which allows them to reach the places where they find food and perform other physiological functions such as mating and reproduction. In addition, snails are oviparous and normally bury their eggs, so they need a moist and soft substrate.
But really, snails don’t usually come out when it’s raining, but later, since raindrops can hurt them by impacting their body and shell. They also do not come out if there is too much water because they cannot move easily in waterlogged terrain and can drown. An optimal situation for them is when the environment has a relative humidity of between 80 and 90%. His preferred hours of the day to go out are at dawn and dusk because they are the times of the day when there is less insolation.
When environmental conditions are unfavorable, snails seek refuge inside their shell and close its opening with the epiphragm, which is a hardened mucous sheet. This helps them to maintain humidity and also to protect themselves from the entrance of predators. In this state they can resist for a long time, during which they do not need to eat because their metabolism is very slow and they do not expend energy. In the case of slugs, which have very small shells or no shells, they bury themselves, take refuge in cracks in wood or rocks or take shelter in areas near water.
Lola Bragado Alvarez She is a biologist and curator of the mollusk collection of the National Museum of Natural Sciences (CSIC).
Question submitted by Ruth Lazkoz.
Coordination and writing:Victoria Bull
we answer is a weekly scientific consultancy, sponsored by theDr. Antoni Esteve Foundationand the programL’Oréal-Unesco ‘For Women in Science’, which answers readers’ questions about science and technology. They are scientists and technologists, members ofAMIT (Association of Women Researchers and Technologists), which answer those questions. Send your questions to[email protected]or by Twitter #werespond.
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