This 'Wandering Meatloaf' Chiton Has Rare Iron Teeth

For the first time, a rare iron mineral has been found in the teeth of a living organism.

A team of scientists from the Northwestern University has discovered a surprising ingredient in the chiton's rock-hard teeth: a rare, iron-based mineral previously only found in rocks. Santabarbaraite, the hardest and stiffest known biomineral, coats those teeth: it's up to three times as hard as human enamel and mollusk shells. Which is strong but lightweight, helps harden the root of the mollusk's teeth. 

The research was published in the journal Proceedings of the National Academy of Sciences (PNAS).

The strange mollusk, affectionately known as the "wandering meatloaf," due to its unusual appearance. It can be found along the northern Pacific Ocean's shores from Central California to Alaska, across the Aleutian Islands to the Kamchatka Peninsula, and south to Japan. It lives along rocky coastlines in the lower intertidal and subtidal zones.

The mollusk chiton, formally known as Cryptochiton stelleri, C. stelleri, is the world's largest chiton, measuring up to 35 centimeters in length.

Chiton requires tough teeth because they essentially chew on rocks to scrape off algae and other food substances.  It has several dozen rows of teeth on a slender, flexible, tongue-like appendage known as a radula, which it uses to scrape algae off rocks. 

"This mineral has only been observed in geological specimens in very tiny amounts and has never before been seen in a biological context," says Derk Joester, senior author of the study, in a Northwestern University press release.

He also says that this rare iron mineral has high water content, making it stronger with a lower density. Furthermore, researchers believe that this helps strengthen the teeth of the wandering meatloaf without adding too much weight.

Joester and his colleagues had previously studied chiton teeth, but they wanted to learn more about the stylus — the hollow structure that, like the root of a human tooth, "connects the [chitons'] ultrahard and stiff tooth head to the flexible radula membrane," according to the study.

The scientists examined chiton teeth using various advanced imaging techniques, including spectroscopy, which allows scientists to learn about a material's chemical and physical properties by observing how it interacts with light and other types of electromagnetic radiation.

These analyses revealed the presence of santabarbaraite in the chiton's upper stylus. "This mineral has only been observed in geological specimens in very tiny amounts and has never before been seen in a biological context," Joester stated.

According to the researchers, the new study will help them understand how chiton teeth can withstand the wear and tear of their dietary needs, leading to the development of a 3D printer ink capable of producing ultrahard and durable material.