How a Myosin Gene Dictates Left or Right Coiling in Japanese Snail Shells
Researchers at Nottingham and Tohoku locate the genetic switch controlling body asymmetry in wild Euhadra snails
By Letizia Giugliano
2 min readHuman-Edited, AI-Assisted
Researchers from the University of Nottingham and Tohoku University have identified the specific genetic mechanism determining whether snail shells coil to the left or to the right. The biological discovery links structural variations in the motor protein myosin to early embryonic cell twisting in wild Japanese snails. Published in October 2026, the findings explain how organisms establish fundamental left-right asymmetry without congenital developmental defects.
The cellular motor driving shell handedness
A scientific study published in Phys.org highlights an important biological innovation in understanding developmental symmetry. By investigating wild snails belonging to the genus Euhadra in Japan, researchers determined that shell coiling direction stems from natural differences within a gene that codes for myosin. This protein works alongside cellular scaffolding components to help cells change shape and move during growth.
According to the research team, led by author Alec Martin Lewis and published in the journal Current Biology, subtle amino acid variations in the myosin protein dictate whether embryonic cells rotate clockwise or counterclockwise during early cleavage stages, as reported by Phys.org. This microscopic rotational shift directly establishes the macroscopic left- or right-handed handedness, or chirality, of the adult snail's shell and internal organs.
“It turns out that small changes in a myosin gene produce mirror-image snails, while still producing healthy, viable animals.”
— Angus Davison, lead author, University of Nottingham
Viability and natural selection across mirror forms
In most animal species, internal organ orientation is fixed, and spontaneous mirror reversals typically coincide with severe embryonic malformations. The Euhadra snails present a striking departure from this rule. The investigation reported by Phys.org confirmed that both left- and right-coiling individuals develop normally without signs of pathology or developmental defects.
Genetic analysis showed that both morphological variants are evolutionary lineages of ancient origin, with the left-coiling form displaying definitive signatures of natural selection. The findings offer a sharp contrast to the common pond snail, where an unnatural mutation in an entirely different gene causes leftward coiling alongside severe physical abnormalities, according to Phys.org. Because these natural biological variants arise from wild genomic diversity rather than commercial patents, the findings remain in the public scientific domain to advance fundamental anatomical research.
Crossing the mating barrier in Japanese valleys
Because snails carry reproductive organs on one side of the body, opposing shell chiralities usually introduce physical barriers that prevent mating. However, researchers from Tohoku University and the University of Nottingham managed to observe gene flow between the two morphs by locating a secluded mountain valley in Japan where left- and right-coiling snails routinely pair, as documented by Phys.org.
Study lead Angus Davison noted that while the scientific foundation of chiral molecules earned recognition through a recent Nobel Prize, understanding how living cells translate uniform building blocks into asymmetric organisms remains an active area of study, according to Phys.org. This natural invention of mirror-image viability in snails offers developmental biologists a model to investigate how bilateral asymmetry is established and conserved across the animal kingdom.
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