Most snails live in right-coiled shells, and the general rarity of sinistral gastropods has long attracted comment and wonder, according to the late Stephen Jay Gould. “Aristotle declared them impossible, but d’ Argentville called them uniques, while Geoffroy dubbed them nonpareilles. Since no one has ever developed an even vaguely plausible argument for dextral advantage, the overwhelming predominance of right-handed coiling among gastropods has been a persistent puzzle.”

The asymmetry puzzle is far from completed, but the control of coiling is genetic, and CRISPR is cracking the code. By targeting a gene called Lsdia1 in the species Lymnaea stagnalis, Reiko Kuroda and colleagues from the Tokyo University of Science succeeded in producing sinistrally coiled offspring generation after generation (see their Development paper).

This is the first application of CRISPR to a mollusk and is expected to have important implications for the understanding of the left-right asymmetry in invertebrates as well as vertebrates, including humans.

Neurobiologists should also take note of Kuroda’s guess about the future: “As we have established gene editing technique for this snail, which is often used in the study of perception, learning and memory, I hope that our work will help this snail become a model organism for human disease research.”