Photo Credit: Professor Angus Davison
Scientific Frontline: Extended "At a Glance" Summary: Snail Shell Chirality
The Core Concept: The physical coiling direction, or chirality, of a snail shell is determined by natural variations in a gene that produces the protein myosin.
Key Distinction/Mechanism: Small changes in the myosin protein dictate whether cells twist clockwise or counterclockwise during the earliest stages of embryonic development, setting the permanent chiral direction for the adult snail’s shell and internal organs without causing disease or pathology.
Origin/History: Researchers from the University of Nottingham and Tohoku University published these findings in Current Biology in October 2026, based on studies of wild Euhadra snails in a Japanese mountain valley where both left- and right-coiling types successfully interbreed.
Major Frameworks/Components:
- Myosin gene variation naturally dictates physical asymmetry.
- Myosin proteins interact with other cellular proteins to construct the cell scaffold and drive cellular movement.
- Embryonic cellular twisting establishes the lifelong anatomical handedness of the organism.
- Natural selection shows evidence of supporting the ancient "lefty" phenotype within this specific snail population.
Branch of Science: Genetics, Evolutionary Biology, and Developmental Biology
Future Application: Establishing the molecular mechanisms of chirality in snails provides a comparative model for investigating how left-right body asymmetry develops in other animals, including humans, and why deviations typically result in embryonic defects.
Why It Matters: While most animals exhibit a rigidly fixed anatomical asymmetry where reversals cause severe developmental problems, these snails produce healthy, viable mirror-image variants, offering critical insights into the biological rules governing physical handedness and organ placement.
Scientists have discovered a gene that determines whether Japanese snails develop shells that are left- or right-coiling, with implications for understanding the underlying handedness of our own bodies.
Researchers from the University of Nottingham and Tohoku University studied wild Euhadra snails in Japan to understand what makes one snail a mirror image of another.
They found that the coiling direction, or chirality, of a snail shell is due to natural differences in a gene that makes a protein called myosin. Myosin helps cells move and change shape by working with other proteins to make the cell scaffold.
The researchers believe that a few small changes in the myosin protein affect how cells twist—either clockwise or counterclockwise—in the earliest stages of development. This sets the direction for the chiral development of the adult snail’s shell and body organs.
In ways that we do not fully understand, the chirality of the basic building blocks of life ends up making bodies that are themselves also handed, or chiral. This is the foundation for our hearts being on the left-hand side of our bodies and snail shells that usually coil to the right. But while the majority of snails have shells that are right-coiling, a good number are left-coiling, and 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.
The finding is important because it helps us understand the common factors by which diverse animals develop their left and right sides. It is also timely because solving the mystery of how chirality comes about received a Nobel Prize last week.
Unlike snails, nearly all other animals show the same fixed asymmetry, and rare reversals of body organs are often associated with problems during embryonic development.
In comparison, the team found that the left- and right-coiling versions of the Japanese snail develop normally as embryos, without any evidence of disease or pathology. Both the left- and right-coiling versions are ancient, but the “lefty” version shows evidence of natural selection.
In other snails, left- and right-coiling versions are not usually able to mate because the genitals are on opposite sides. The key to the new work was finding a valley deep in the mountains of Japan where both left- and right-coiling types are able to mate and exchange genes.
The researchers also compared their findings with a pond snail in which lefties are rare. In pond snails, a mutation in a different gene makes snails with left-coiling shells but also causes them to develop abnormally.
Since other animals ordinarily have a fixed left-right body plan, the work with snails can help us understand why other animals do not 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.
Published in journal: Current Biology
Title: An ancient polymorphism in myosin I a/b determines chiral variation in Japanese Euhadra snails
Authors: Alec Martin Lewis, Yasuto Ishii, Shun Ito, Kazuki Kimura, Margrethe Johansen, Alistair Nicholas Hume, Christopher Moore, Tom Hartman, Daniel John Jackson, Satoshi Chiba, Takahiro Hirano, and Angus Davison
Source/Credit: University of Nottingham | Charlotte Wall
Edited by: Scientific Frontline
Reference Number: gen101626_01