Genomic secrets of scaly-foot snail from hydrothermal vents

Despite an extreme environment characterized by high pressure, high temperature, strong acidity and low oxygen level which resembles living condition in pre-historic time, hydrothermal vents harbor a diverse amount of creatures -- most of which have huge potential for biomedical and other applications. Among other inhabitants of such difficult environment, Scaly-foot Snail, also known as "Sea Pangolin," is of particular interest to marine scientists.

Scaly-foot Snail is the only extant gastropod (a major invertebrate animal, commonly known as snails and slugs,) alive that possesses armor-like scales -- an otherwise very common feature for gastropod during the Cambrian time over 540 million years ago. This snail is also the only organism in the world known to incorporate iron into its exoskeleton, and is also one of the top ten astounding marine species of the decade (2007-2017). Little is known, however, about its genome and unusual morphology, as the creature is extremely difficult to locate and collect.

Now, a research team led by Prof. QIAN Peiyuan, Chair Professor of HKUST's Department of Ocean Science and Division of Life Science, managed to collect 20 scaly-foot snails at around 2,900 meters below sea level from the Indian Ocean in collaboration with researchers from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and analyze the snail's genome sequence.

Contrary to many scientists' expectation that the creature contains some new special genes that give rise to its bizarre morphology, the team actually discovered that all of the snail's genes already existed in other mollusks such as squid and pearl oyster, and the snail's gene sequence has remained almost unchanged throughout its evolution. The 25 transcription factors (a key protein that regulates many downstream gene expression levels) which contribute to the snail's scale and shell formation, as the team identified, have also contributed to the formation of many other unique hard-parts in Mollusca -- such as operculum in gastropods, beak in squid, spicule in chiton, or chaetae in polychaetes.

"Although no new gene was identified, our research offers valuable insight to the biomineralization -- a process where the clustering, positioning and on and off switching of a combination of genes defines the morphology of a species," Prof. Qian said. "Uncovering Scaly-foot Snail's genome advances our knowledge in the genetic mechanism of mollusks, laying the genetic groundwork which paves the way for application. One possible direction is how their iron-coated shells withstand heavy blows, which can provide us insights on ways to make a more protective armor."

The findings were recently published in the scientific journal Nature Communications.

The study of genome sequencing of organisms often brings breakthrough to biomedical and other sectors. An enzyme of a microbe that lives in such vents -- for example, was recently used for the detection of COVID-19 as well as other viruses such as AIDS and SARS.