May 28, 2013
Snail Shell Coiling Programmed By Protein Patterning
Snail shells coil in response to an lopsided protein gradient across their shell mantles, finds research in BioMed Central's open access journal EvoDevo. In contrast the shell mantle of limpets, whose shells do not coil, have a symmetrical pattern of the protein Decapentaplegic (Dpp).
There are many hundreds of different kinds of gastropods (slugs snail and limpets) - second only in number of species to insects. They have adapted to live on land as well as in fresh water and marine environments, and have altered their physiology to survive in different habitats and to exploit different niches. The ancestral snail is thought to have had a coiled shell but during evolution some snails have lost their shells to become slugs, and some, limpets and false limpets, have independently lost the ability to coil their shells.
In all four animals tested, limpets Patella vulgata and Nipponacmea fuscoviridis, and the right-hand coiled pond snail Lymnaea stagnalis along with a sinistral coiled lab-developed snail, dpp expression matched shell shape. There was also a Dpp protein gradient spreading away from this which was also symmetrical in limpets but had left/right asymmetry for the pond snails, matching the handedness of shell coiling.
Keisuke Shimizu, who led this study, commented, "This molecular mechanism driving for shell coiling persists from early developmental stages though adult life as the shell is replaced. It also provides an explanation for how shell coiling has been lost several times during the evolution of gastropods by the relatively easy loss of asymmetric Dpp."
On the Net: