Scientists find gene that makes some snails’ shells coil left; the same species that twist their genitals to mate

Like humans, snails can be right-handed or left-handed, and scientists have found a gene that determines whether the swirls of their shells will be left- or right-coiling. A team of researchers from the University of Nottingham and Tohoku University studied wild Euhadra snails found in Japan and Korea to understand what makes the soft-bodied animal a mirror image of one another.

Wild Euhadra snails are unique because the whole species within the genus is entirely left-coiled, and in contrast, all other snail species found elsewhere are right-coiled.

The researchers observed that chirality, or the coiling direction of a snail shell, is because of a natural differences in a gene which encodes a protein named myosin, which mainly helps muscle contraction.


The paper published in Current Biology on October 16, finds that a few small changes in the myosin protein dictate how cells twist (clockwise or counterclockwise) in the earliest stages of development. Eventually, this sets the direction for the chiral development of the adult snail's shell and body organs.

“But while the majority of snails have shells that are right-coiling, a good number are left-coiling and a few species have both coiling types. Until now, we had no idea how they do this. It turns out that small changes in a myosin gene produce mirror-image snails, while still producing healthy, viable animals,” said Professor Angus Davison, lead author of the study.

“Unlike snails, nearly all other animals show the same fixed asymmetry, with rare reversals of body organs often associated with problems during the development of the embryo,” the University of Nottingham explained in a press release.

Snails, in contrast, develop their left- and right-coiling versions normally as embryos, without any disease or pathology in the future.

“Both the left- and right-coiling versions are ancient, but the ‘lefty’ version shows evidence for natural selection,” the University noted.

It was believed that left- and right-coiling snails are not usually able to mate, because the genitals are on opposite sides. But Davison, in his 2017 paper, discovered that the mirror-image snails somehow found a way to twist their flexible genetals to mate face-to-face.

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The researchers also compared their findings with a pond snail, which is mostly right-handed. There, a mutation in a different gene caused them to be left-coiled, but they developed abnormally.

“Since other animals ordinarily have a fixed left-right body plan, the work with snails can help to understand why other animals don't vary. There is still a deep mystery in understanding how snails use molecules of the same chirality to make bodies and shells that have a variable chirality,” concluded Professor Davison.

A week back, French scientist Henri B. Kagan and Japan's Kenso Soai were awarded the Nobel Prize in chemistry for solving the mystery of how chirality comes.