First evidence of sleep in snails

Feb 18, 2011 by Lin Edwards report
Image credit: The Company of Biologists Limited

(PhysOrg.com) -- Scientists in Canada noticed pond snails spent around 10 percent of their time attached to the side of their tank with their tentacles partly withdrawn, their shells hanging away from their bodies, and with their feet symmetrical and relaxed. The researchers decided to do some experiments to find out if the snails were asleep or just resting, and their results provide the first evidence that gastropods sleep.

There is no single characteristic that defines but sleep is deduced from a number of factors such as being unresponsive and hard to rouse, and adpoting a characteristic position. To determine if their did sleep, Associate Professor Richard Stephenson and Dr Vern Lewis of the University of Toronto observed pond snails (Lymnaea stagnalis) in their tanks and cataloged their behavior.

The researchers reasoned that if the snails were rather than merely resting, they would respond less to stimulation and would withdraw their bodies into their shells sluggishly when prodded with a metal rod, for example. They tested the responses of active and apparently sleeping snails to being tapped on the shell, prodded with a rod, and having their appetites simulated by exposing them to sucrose solution.

The results of their experiments showed that the active snails responded twice as quickly to physical stimulation and seven times faster to appetite simulation than the immobile snails, so it appears that the resting snails were actually asleep rather than just relaxing.

The researchers then monitored eight snails over a period of 79 days to monitor patterns of sleeping and see if the amount of light exposure affected their behavior. They found that the followed a two to three day period rather than a 24 hour cycle with clusters of around seven bouts of sleeping over a 13-15 hour period followed by over 30 hours of uninterrupted activity. They did not need to make up for lost sleep, a process known as sleep rebound.

Dr Stephenson said snails do not sleep at a regular time as most other animals do, and they need very little sleep because their lifestyles are not mentally demanding, so they probably do not need tight controls over their sleeping patterns.

Sleep is believed to be important to many biological processes such as memory formation, but there are still many unanswered questions. The researchers think a study of sleep in simple animals such as pond snails could be useful in aiding our understanding of cellular functions in sleep.

The paper was published in the Journal of Experimental Biology.

Explore further: Lights, camera, blossom! Disney films inspire floral fantasy

More information: Behavioural evidence for a sleep-like quiescent state in a pulmonate mollusc, Lymnaea stagnalis (Linnaeus), First published online February 9, 2011. Journal of Experimental Biology 214, 747-756 (2011) doi: 10.1242/jeb.050591

Related Stories

Snails on methamphetamine

May 28, 2010

Crystal meth (methamphetamine) is a highly addictive drug that seduces victims by increasing self-esteem and sexual pleasure, and inducing euphoria. But once hooked, addicts find the habit hard to break. Barbara ...

Atlantic snails are increasing dramatically in size

Mar 24, 2009

A Queen's University biologist has discovered that the shell lengths of snails in the northwest Atlantic Ocean - an important member of the Atlantic food chain - have increased by 22.6 per cent over the past ...

Can you make a snail forget?

Jun 29, 2010

Predator scent enhanced the ability of pond snails (Lymnaea stagnalis) to form memory following training, whilst overcrowding and reduced calcium had a blocking effect.

Recommended for you

A molecular compass for bird navigation

1 hour ago

Each year, the Arctic Tern travels over 40,000 miles, migrating nearly from pole to pole and back again. Other birds make similar (though shorter) journeys in search of warmer climes. How do these birds manage ...

100,000 bird samples online

3 hours ago

The Natural History Museum (NHM) in Oslo has a bird collection of international size. It is now available online.

New genetic technologies offer hope for white rhino

5 hours ago

With support from the Seaver Institute, geneticists at San Diego Zoo Institute for Conservation Research are taking the initial steps in an effort to use cryopreserved cells to bring back the northern white rhino from the ...

Cats put sight over smell in finding food

20 hours ago

Cats may prefer to use their eyes rather than follow their nose when it comes to finding the location of food, according to new research by leading animal behaviourists.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

zevkirsh
1 / 5 (1) Feb 19, 2011
yes, but do they dream of slimy sheep?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.