How the snail's shell got its coil

May 14, 2019

If you look at a snail's shell, the chances are it will coil to the right. But, occasionally, you might find an unlucky one that twists in the opposite direction - as fans of Jeremy the lefty snail will remember, these snails struggle to mate with the more common rightward-coiling individuals.

This chirality (direction of coiling) of snail shells is an outward manifestation of left-right asymmetry: a phenomenon seen across animal evolution and extending to humans - your heart is (probably) on your left side, while your liver is to the right. But how does this asymmetry come about? Researchers from Japan, writing in the journal Development, think they now have a definitive answer - for one species of freshwater snail (Lymnaea stagnalis) at least.

Successfully applying CRISPR gene editing technology to molluscs for the first time, Masanori Abe and Reiko Kuroda (working at Tokyo University of Science, but recently relocated to Chubu University, Japan), have now made snails with mutations in a gene called Lsdia1, which had previously been suggested - but not conclusively proven - to be involved in snail shell coiling; snails without a functional copy of Lsdia1 produce offspring with shells that coil to the left, showing that this single gene is responsible for rightwardcoiling. Surprisingly, the researchers could see signs of asymmetry at the earliest possible stage of development - when the snail embryo was just a single cell. Moreover, the mutant snails could be reared to adults, when they produced exclusively leftward-coiling offspring. According to Kuroda: "It is remarkable that these snails with reversed coiling are healthy and fertile, and that this coiling can be inherited generation after generation (we now have 5th-generation leftward-coiling snails). Further, these results may have an implication for snail evolution and speciation - given that left- and rightward-coiling snails probably wouldn't interbreed."

It's still not clear how Lsdia1 might control left-right asymmetry: the gene encodes a formin, a protein that is involved in regulating the cell's internal skeleton, but more work is needed to understand how this influences the cellular behaviours that control handedness - which is something Kuroda and her colleagues are actively working on. But given that genes like Lsdia1 are found throughout the animal kingdom, similar mechanisms for controlling left-right asymmetry could be at play in other species - including our own.

As Kuroda says: "Although diverse mechanisms have been proposed for different animals, we think a unified mechanism, involving formins and cellular chirality, is probable". So while it may seem a big leap from snail shell coiling to human left-right asymmetries, it's possible that future studies on how Lsdia1 works in snails might eventually help us understand why some babies are born with their heart on the right (which is of course the wrong) side of their chest.
If reporting this story, please mention the journal Development as the source and, if reporting online, please carry a link to:

REFERENCE: Abe, M. and Kuroda, R. (2019) The development of CRISPR for a mollusc establishes the formin Lsdia1 as the long-sought gene for snail dextral/sinistral coiling (Development, in press) doi: 10.1242/dev.175976

The Company of Biologists

Related Snails Articles from Brightsurf:

Planktonic sea snails and slugs may be more adaptable to ocean acidification than expected
Pteropods, or ''wing-footed'' sea snails and slugs, may be more resilient to acidic oceans than previously thought, scientists report.

Understanding the movement patterns of free-swimming marine snails
New research looks at the swimming and sinking kinematics of nine species of warm water pteropods (sea snails) to shed light on their ecology, predator-prey interactions, and vertical distributions.

Poetry in motion: Engineers analyze the fluid physics of movement in marine snails
In a new interdisciplinary study that combines intellectual curiosity with awe, researchers show in detail that the swimming and sinking behaviors of tropical marine snails are influenced by body size and shell shape, as predicted from fluid physics theory.

St Petersburg University scientists count all the tiny snails in the Arctic
St Petersburg University Scientists have summarised all the known information about Arctic snails that have dimensions less than five millimetres.

Two lefties make a right -- if you are a one-in-a-million garden snail
A global campaign to help find a mate for a left-coiling snail called 'Jeremy' has enabled scientists to understand how mirror-image garden snails are formed.

Tiny fly from Los Angeles has a taste for crushed invasive snails
As part of their project BioSCAN the scientists at the Natural History Museum of Los Angeles County (USA) have already discovered plenty of minute insects that are new to science, but they are still only guessing what the lifestyles of these species are.

Genomic research led by HKBU unravels mystery of invasive apple snails
Biologists from Hong Kong Baptist University (HKBU) have led a study to sequence and analyse the genomes of four apple snail species in the family Ampullariidae.

Snails show that variety is the key to success if you want to remember more
Neuroscientists at the University of Sussex have revealed the factors that impact on memory interference, showing that a change is as good as a rest when it comes to retaining more information.

Pseudohermaphrodite snails can help to access how polluted the Arctic seas are
Ivan Nekhaev, a postdoc at St Petersburg University, studied snails of the genus Boreocingula -- tiny gastropods as small as half a centimeter -- and first discovered that Arctic micromolluscs can show signs of pseudohermaphroditism.

How the snail's shell got its coil
Researchers from the Tokyo University of Science, Japan, have used CRISPR gene editing technology to make snails with shells that coil the 'wrong' way, providing insights into the fundamental basis of left-right asymmetry in animals.

Read More: Snails News and Snails Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to