The scaly-foot snail lives over a mile deep at the hydrothermal vents in the Indian Ocean. It has a unique shell that is encased in an outer layer of scales of iron and sulfur. These kinds of scales were common in the Cambrian period 540 million years ago (300 million years before the first dinosaurs), but today they are only found in the scaly-foot snail.

Researchers from the Hong Kong University of Science and Technology were interested in identifying the genes that led to the scales on the scaly-foot snail. After using a submersible to collect specimens from 2,900 meters (1.8 miles) below sea level, scientists extracted and sequenced the snails’ DNA as well as RNA from different parts of the snails’ bodies. The researchers found 25 genes that control the formation of the scaly-foot snail’s scales and shell. RNA revealed that the snail’s body only read these genes in cells on parts of the body where the hard foot and shell were created. Surprisingly, none of these genes were unique to the scaly-foot snail. All these genes have previously been found in other mollusks, including other snails and squids, where they are expressed to make beaks and shells, for example. Likewise, the scaly-foot snail’s genes seem to be very old and not to have evolved significantly over the last 540 million years. This would suggest that mollusks are generally all using the same genes but are controlling which genes are read in their bodies to make the different shells, feet, and beaks that appear in different mollusks.

In the future, the researchers would like to elucidate how the genes are turned on and off in different parts of an animal’s body to create the variety of hard parts found in the mollusk family. They would also like to further understand the evolutionary history of the scaly-foot snail, a challenging task given the genetic similarity between it and other related mollusks, as well as the mechanical properties of how to iron scale structure protects the ocean-dwelling snail.

Managing Correspondent: Emily Kerr

Press Article: Researchers unlock genomic secrets of scaly-foot snail  

Original Scientific Article: The Scaly-foot Snail genome and implications for the origins of biomineralised armour Nature Communications

Image Credit: Chong Chen, Katsuyuki Uematsu, Katrin Linse & Julia D. Sigwart