Some snails like certain land snails can sleep up to 3 years at a time.
The certain land snails that can sleep up to 3 years at a time, do so in a state of deep hibernation or estivation.
The state of deep hibernation or estivation that some snails can do is described as a 3 year sleep.
The snails that sleep up to 3 years at a time, do so to survive extreme droughts, or cold by sealing themselves in their shells with mucus in order to conserve moisture and energy.
However the sleeping for 3 years that snails do, is not a typical or regular sleep like daily sleep.
Instead the 3 year sleep that snails do, is a profound hibernation, (cold) or estivation (warm/dry) state called torpor.
Snails sleep for the 3 years as they need high humidity to survive, and if the weather is too dry or to cold for an extended period, the snails will enter the dormant state to prevent dehydration and help them survive.
The snails survive by sealing their shell opening with a hardened mucus layer, that is known as an epiphragm and then they slow their metabolism drastically.
In normal conditions, snails don't have a 24 hour sleep cycle, although they instead snails cycle through about 15 hours of sleep, that is then followed by 30 hours of activity.
Although snails can sleep for 3 years at a time, it's not all that common, and snails will also wake up sooner if their environmental conditions improve.
Land snails are terrestrial gastropod mollusks that breathe air, have a shell (though slugs are shell-less relatives), and move on a muscular foot, leaving a slime trail.
The land snails are found globally in diverse habitats, from forests to cities, and are known for their slow movement, nocturnal habits, and need for moisture, often eating decaying plant matter and requiring calcium for their shells.
Land snails are classified as mollusks (phylum Mollusca), class Gastropoda, adapted for life on land.
Land snails usually possess a shell, a muscular foot for locomotion, and 2 pairs of tentacles, which includes upper tentacles for eyes and lower tentacles for smell and touch.
Snails that are on land breathe through a lung like organ, with a visible opening, called pneumostome on the right side.
And land snails are also primarily herbivores and eat decaying plants, fungi and sometimes protein and need calcium for their shell growth.
Land snails are also often nocturnal or crepuscular and are active at dawn/dusk and most active in warm, humid conditions.
The land snails can also retract into their shell and seal the opening with a mucus layer called "epiphragm" to survive dry periods also known as aestivation.
Land snails are also found worldwide in nearly all terrestrial environments, which includes deserts and tropics, except in Antarctica.
Land snails are also common in wetlands, leaf litter, gardens and forests.
Common examples of land snails are the garden snail also known as the Helix Aspersa, which is a common European species of land snail
And the Giant African Land Snail or Achatina fulica, which is a very large, invasive species of land snail that is known for damaging agriculture.