Nudging a Republican Snail Into a Democrat


Cristina Grande and Nipam Patel

DIFFERENCES In this pair of land snails, the one on the right, with the shell opening on the right, is the more common of the species.

My children and I recently "caught" a mud snail off the coast of New Jersey, and it got me thinking...

I've always been fascinated that some snails have left-handed shells and others right-handed. Forgiving the "left/right" political belief reference, do you think it would be possible to nudge a snail towards one form over the other? If so, how could you do it?

I've been exploring this question as one of my research projects, and it turns out that it is very difficult to do. {My students and I, along the way, have learned a lot about snails. See our commentary on this question in The New York Times here. }

A research group at The University of Tokyo did figure out a way, by literally pushing the cells away from the direction in which they would normally develop, at an early stage of development:

we used two glass rods to push the animal surface of each blastomere in the directions opposite to the normal third cleavage

Simply brilliant!


This scheme summarizes the development of left- and right-handed snails from the one-cell stage to mature adults. In L. stagnalis, reversing the chirality by micromanipulation at the first or second cleavage stage does not alter the organismal chirality, as the manipulated embryos revert to form eight-cell embryos of original handedness (thin arrow). In contrast, embryos whose chirality is reversed by micromanipulation at the third cleavage grow to chirality inverted juvenile and then to healthy and fertile adult snails, with oppositely-coiled shell and situs inversus viscerum (thick arrow). nodal and Pitx expressions are also reversed by this manipulation. Dextralized snails are produced from sinistral snails without SD (spiral deformation), a unique feature observed only at the third-cleavage metaphase-anaphase of dominant dextral snails, and directly linked to the handedness-determining gene(s).

It turns out that, for a snail, whether you're "right" or "left" is a matter of survival:


Watch the video here.

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