The mind of a snail

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The mind of a snail

Postby ittybittynickel on Thu Mar 17, 2005 2:44 am

The mind of a snail

If you give a marine snail an easy life, it will, like most creatures, sit back, think about things, then eat a leisurely meal. On the other hand, if you introduce an element of risk into its neighbourhood, it will display some sharp-witted ways, such as figuring out hunting tricks from a repertoire it has not used in a million years or more.

To feed, snails use a body part called a proboscis radula - a tongue with teeth on the end of it - along with a cocktail of chemicals that soften the shells of its prey.

Drilling through a clam shell using only a tongue is not a task to be undertaken lightly. If the snail attacks at the centre of the clam - the

thickest portion of the shell - it can take six days to get through to the meal. This leaves it potentially vulnerable for quite some time to predators or simply to other competitors who want to steal its food after it does all the work.

The alternative - but potentially riskier - strategy is to drill at the edge of the clam shell. This approach can take only two days, but it leaves the snail at risk of having its drilling tongue cut off if the clam opens and closes its shell.

Gregory Dietl and researchers at Yale University, USA, looked at thousands of fossil clam shells from before and after the extinction and compared them with modern shells. Edge-drilled shells were common before the Pleistocene era, but after it, they disappeared entirely. No modern shells show edge-drilled holes.

They then experimented with live snails in the lab, creating environments both with and without the presence of predators. When no predators were present, the snails conducted their leisurely drilling in the centre of the clams' shells, just like they do in the wild.

Yet when the snails – who are never exposed to predators in the wild, and have not done any edge drilling in nearly 2 million years - were exposed to predators in the lab, they rapidly resumed the edge-drilling behaviour, in some cases taking only a week for a single animal.

It sounds suspiciously like the snails - whose reputation for intelligence is not widespread - considered the problem and figured out a solution.

People have known for a hundred years that invertebrates can learn, said David Glanzman, Professor of Physiological Science and Neurobiology at the University of California, Los Angeles, USA. "When you look at the neural basis of learning in marine snails, it turns out to be similar or identical to the neural basis in higher organisms."

These nervous-system components evolved very early, Glanzman explained, "hundreds of millions ago, and you can see them in very simple invertebrate organisms. Their nervous systems have the neural mechanisms that our brains use."

Source: Washington Times
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Ancient Snail Wars

Postby Pollux on Thu Dec 07, 2006 9:39 am

Ancient Snail Wars

A three million year war between snails and their prey has been described by two American palaeontologists.

The research paper detailing this epic battle have been published on-line.

Peter Roopnarine and Amy Beussink studied fossil snails and other shellfish from Florida. The snails preyed upon the shellfish by drilling holes through the shells and attacking the soft animal inside. Both the shells with bored holes and snails are preserved as fossils.

According to the Theory of Escalation, more commonly known as the Biological Arms Race, one of the main factors in evolution is the presence of biological enemies. Prey develop better defences while predators develop better ways of attacking prey.

Roopnarine and Beussink looked at what happens to the relationship between hunters and the hunted when the prey species is replaced by a similar but subtly different relative. Different species of snail are very specific about the size of their quarry, as well as the drilling location on the shell.

Roopnarine and Beussink found that shellfish responded to the snail's onslaught by evolving thicker shells, which were harder for the snails to penetrate. Further, when the shellfish was replaced by another species, predatory snail species responded initially by selecting smaller prey. As time progressed the snails were able to attack larger individuals of the new prey species.

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