Hiromi Takahashi

Most snail shells coil to the right. This single gene may be the reason why

If you ever come across a group of snails, chances are most of their shells coil to the right. Until recently, scientists didn’t know why this was the case. Now, researchers have found the gene that makes this right-coiling happen in freshwater snails (Lymnaea stagnalis).

For the first time, scientists used CRISPR, a tool that edits genes, successfully in snails. They mutated a gene called Lsdia1, which had been suggested in previous studies to be involved in shell coiling. Gastropods without a functional version of the gene produced offspring with shells that coiled to the left (pictured), researchers report today in the journal Development. These changes in shell coiling could be seen as early as the embryo stage.

It’s still not clear how Lsdia1 controls shell coiling all by itself. Scientists think it may encode a special protein that is involved in regulating cells’ internal skeleton, but more tests still need to be done.

Genes like Lsdia1 are found throughout the animal kingdom, meaning similar mechanisms may be influencing left-right asymmetry in other species, scientists note.