Snail Sleep: A Closer Look at Their Resting Behavior

Snail Sleep A Closer Look at Their Resting Behavior

Do snails sleep? The short answer is yes. Snails do sleep, but since they do not have a centralized nervous system (like humans), their sleep patterns are not as well-defined or predictable. Generally, they sleep for short periods throughout the day and night, rather than in one continuous period.

When snails sleep their state is characterized by postural relaxation of the foot, mantle, and tentacles, and cessation of radula rasping.

Many people mistake a snail’s typical sleep for a state of hibernation. To distinguish between these two states, it is important to understand why snails sleep and how long they typically sleep for.

In this article, I will explore these and other related questions by referring to scientific research.

Snails’ Behavior

Any direct visual observation of snails in the tank will reveal that it can be divided into 6 categories:

  1. locomotion,
  2. feeding,
  3. defensive withdrawal,
  4. oviposition,
  5. respiration and
  6. quiescence (inactivity state).
Due to the fact that snails lack sleep as we understand it in the usual sense, for example, for humans, the state of inactivity has been named “quiescent”.

Quiescent behavior refers to a state of inactivity or rest in which an organism appears to be sleeping or at rest, scientists call it a sleep-like behavior.

Unlike the five types of active behavior listed above, this state of inactivity is closest to the description of sleep for snails.

Quiescence State and Sleep State

According to the study, quiescence is not absolutely equal to sleep, the point is that resting wakefulness, paralysis, hibernation, torpor, akinesis, diapause, aestivation, anesthesia, and coma all share almost the same characteristic.

Therefore, scientists use other characteristics that define the sleeping state. To be considered sleep-like, a state must meet 2 criteria.

  1. The inhibition of motor output must be quickly and easily reversible.
  2. The suppression of sensory responsiveness must also be reversible, which differentiates it from alert rest.

Results of the experiments showed that quiescent snails responded even though significantly slower, and had a lower initial bite rate compared to active snails.

Signs of Sleep in Snails

  1. The aspect ratio of the foot decreases relative to that during locomotion, becoming less elongated both anteriorly and posteriorly, but the snails did not withdraw fully into the shell.
  2. The tentacles also shorten to a variable extent (but did not withdraw completely) and appeared less turgid and sometimes curved.
  3. Rasping movements of the radula are absent.
  4. Quiescent snails remain attached to the substrate. However, when attached to a vertical surface, the shell was often observed to fall away slightly, suggesting partial relaxation of the columella muscle.

During sleeping, snails usually do not assume any particular orientation or occupy a specific site within the tank.

Note: Snails often fall off the walls of the aquarium even when they are active. Generally, it is not a problem for small aquatic snails but not for large land snails. That is why, it is not recommended to choose an enclosure with high walls for keeping African snails. When falling, the shell can be damaged, causing the snail to become sick. Shell recovery is a complex and lengthy process.

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How Long Do Snails Sleep?

Snails are known to be primarily nocturnal creatures, which means they are more active at night and tend to rest during the day. Also as low-tier animals in the food chain, snails cannot afford to sleep for long, uninterrupted periods as it significantly increases the risk of being eaten.

Therefore, all snail species are found to become spontaneously quiescent at frequent but irregular intervals.

For example, during the study of the state of so-called sleep in the great pond snails (Lymnaea stagnalis). It was found that these snails spontaneously enter a relatively brief (22±1min) quiescent state. Over the long term, pond snails spend about 8-10% of the total time in the quiescent state which equals around about 2-2.5 hours per day.

Obviously, the duration of this state can vary depending on the species. For instance, according to observations, Large African land snails (such as Achatina sp. and Archachatina sp.) spend significantly more time in a sleep state, approximately 4-5 hours.

Difference between Sleeping, Hibernating, and Withdrawal into Shell

Hibernation and sleep are two different states of reduced activity.

  • Hibernation

Snail Hibernation EpiphragmIn snails, hibernation is one of the most widespread strategies to cope with unfavorable conditions (such as low temperatures, inadequate humidity, limited access to food resources, etc.). Snails that are unable to hibernate during unfavorable conditions can die or their species may even go extinct.

In this state, snails enclose themselves into their shells with epiphragm, reduce metabolic activity and temporarily suspend movement, nutrition, and growth. Basically, this mechanism ensures their survival.

Note: The epiphragm is a film made of hardened mucus containing dissolved proteins and grains of calcium carbonate. After sealing the entrance to its shell, the epiphragm dries out. There is a layer of air between the snail’s body and the protective membrane, allowing the snail to breathe.

Interesting fact: Snails have been known to remain dormant for from 2 to 4 years and to become active again when favorable conditions of food and moisture were restored.

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Sleep, on the other hand, is just a state of reduced consciousness. The main difference is that during sleep, the snails’ body metabolic rate also slows down, but the body temperature remains relatively stable.

  • Withdrawal into Shell

This is a dangerous state in which the snail does not wake up on its own. Its body is deeply withdrawn into the shell, and the entrance is not sealed with the epiphragm.

It is important to distinguish between sleep, hibernation, and withdrawal into the shell. Snails can remain in this state for a prolonged period of time, exhibiting symptoms such as lethargy, loss of appetite, and shrinking of the body.

It is essential to identify this condition as early as possible, determine the causes, and begin treatment.

Why Snails Hibernate or Withdraw into Shell

Snails can enter into these states due to several main reasons:

  • Extreme temperature
  • Insufficient humidity
  • Stress
  • Injuries
  • Lack of food
  • Parasites
  • Poor quality of water (for aquatic snails) or substrate (for land species)

If you keep land or aquatic snails as pets, it is important to ensure proper living conditions for them to prevent them from entering hibernation or withdrawing into shells. Thus, regular monitoring and prompt attention to any issues can help keep snails healthy and active.

When a snail enters hibernation naturally, it is recommended to limit its sleep to 1-2 months and no more.

It can be particularly dangerous when the snail wakes up, crawls a bit, and then goes back to hibernating or withdrawing into shell.

The main problem is that each time it wakes up, it loses some moisture (weight) that it does not replace (because it does not eat). As a result, the snail retreats further into its shell. As it wakes up more frequently, it has less energy to build the protective epiphragm, and its body shrinks more am more, making it even harder to wake up.

How to Wake a Snail Up from Hibernation?

If your snail went into hibernation and you decided to wake it up, preparation is necessary.

First of all, you need to prepare optimal water parameters in the tank (for aquatic species) and clean the enclosure, change the substrate, check the humidity (for land snails). In addition, you need to provide all the necessary food.

Once the preparation is complete, you can begin to awaken the snail:

  • Spray the snail with warm water.
  • If it does not wake up, hold the snail under a stream of warm water.
  • Offer food to the snail. Place the snail in the water dish with milk (for land snails).
  • If the snail wakes up, do allow it to fall asleep on its own. After hibernation, the snail’s body will be depleted, and it may not survive a second hibernation.

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Hibernation of Snails in Nature

Hibernation is an absolutely natural process for snails. When the environmental conditions worsen, snails begin to search for a suitable place to hibernate. They search for a suitable spot to do so, with different species preferring different locations.

Some snail species burrow into soil or fallen leaves during droughts and cold weather. Those living in southern latitudes may attach themselves to trees, while mollusks in arid regions attach themselves to plant leaves. Terrestrial snails position themselves in the soil with the opening of their shell facing upward and secrete a substance to seal the entrance to their shell.

During hibernation, snails can lose up to 25-30% of their body weight. The most significant weight loss occurs in the first 2-3 weeks of hibernation.

In Conclusion

Snails do sleep, but since they lack a centralized neural system, their sleep patterns are not as well-defined or predictable as those of humans. Therefore, the term “quiescent” most closely resembles how snails sleep, and it has been used to describe the condition of inactivity.

Snails sleep for brief intervals both during the day and at night, which is indicated by postural relaxation and cessation of radula rasping. Depending on the species, they generally sleep from 2-5 hours per day.

References:

  1. Stephenson, Richard, and Vern Lewis. “Behavioural evidence for a sleep-like quiescent state in a pulmonate mollusc, Lymnaea stagnalis (Linnaeus).” Journal of Experimental Biology214, no. 5 (2011): 747-756.
  2. Gallup, Anna Billings. “LAND SNAILS.” The Museum News (Brooklyn Institute of Arts and Sciences)3, no. 3 (1907): 49-52.
  3. Renwrantz, Lothar, and Frank Spielvogel. “Heart rate and hemocyte number as stress indicators in disturbed hibernating vineyard snails, Helix pomatia.” Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology160, no. 4 (2011): 467-473.

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