Related BBC sites

Page last updated at 09:22 GMT, Wednesday, 8 December 2010
'Left-handed' coiling snails survive more snake attacks
By Victoria Gill
Science and nature reporter, BBC News


How a snail shell coil stops snake jaws

Snails with shells that coil anti-clockwise are less likely to fall prey to snakes than their clockwise-coiling cousins, scientists have discovered.

The arrangement of the snakes' teeth makes it difficult for the reptiles to grasp these "left-handed" snails.

The effect of this advantage on the survival of Satsuma snails is so great, say the researchers, that they could separate into a distinct species.

Biologists in Japan report the finding in the journal Nature Communications.

Angle of attack

Satsuma snails come in two forms: those which have shells that coil anti-clockwise, considered sinistral or "left-handed" and those that coil clockwise, considered "right-handed".

Land snails copulate face-to-face, and a snail with a reverse-coiled shell has its whole body reversed - including the position of its genitals.

This means that oppositely coiled individuals are anatomically incompatible when it comes to mating, so the scientists were puzzled as to why "reverse-coiled" snails continued to survive and evolve.

X-ray of snake's jawbone
The arrangement of the snake's teeth makes it difficult to grasp the snails.

To investigate, the team, led by Masaki Hoso from Tohoku University in Sendai, set up "predation experiments".

They observed snail-eater snakes' (Pareas iwasaki) as they attempted to eat the snails.

To consume the soft-bodied molluscs, the predators had to extract them from their shells.

"When attacking, the snake always tilts the head leftward," Dr Hoso told BBC News.

The snake grasped the snail with its upper jaw and inserted its lower jaw into the shell to extract the soft body.

The "right-handedness" of this sequence of movements, Dr Hoso explained, means that the snake "cannot grasp [left-handed] or sinistral snails well".

The scientists wrote: "This study illustrates how a single gene for reproductive incompatibility could generate a new species by natural selection."

Print Sponsor

UK hunt for stately snail begins
26 Aug 10 |  Earth News
Turtles are 'right-flippered'
10 Nov 09 |  Earth News
Evolution is slowing snails down
11 May 09 |  Earth News



From Science/Environment in the past week


Sign in

BBC navigation

Copyright © 2019 BBC. The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.

Americas Africa Europe Middle East South Asia Asia Pacific