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One Fish, Two Fish, Fluorescent-Green, Iron-Toothed Fish

As far as fish go, the pacific lingcod is pretty average. Regular enough for Karly Cohen, a doctoral candidate at the University of Washington, to consider them “models of study” for fish teeth.


But 20 percent of the lingcod population has fluorescent green or blue meat, which, for some fish-inclined humans, happens to be quite tasty fried. (Imagine foregoing the traditional red or white meat for dinner: “Fluorescent blue filet, pan-fried, please.”)


Oh, and the 500 or so teeth that line their jaws: they’re sharp. They are shaped like needles. They can pierce an armored crab and can handle a slippery squid. Like Nemo and Dory, you will probably not fancy a face-to-face meeting with such a creature in the middle of a dark trench in the depths of the ocean.


Cohen wondered: Just how these fish are able to maintain their needle-like teeth so sharp? Is there a special ocean rock against which the lingcod files their teeth? Or perhaps a fish tooth sharpener exists that is unbeknownst to humans?


According to a study published in October in the Proceedings of Royal Society B, the answer is neither. The answer is: regeneration.


Every day, the lingcod grows and replaces 3 percent of its teeth. That’s 20 brand new chompers. In human terms, it would be like losing one tooth and growing it back within 24 hours.


Sharp teeth are what make lingcods, well, lingcods. “The duller a lingcod’s teeth are, the harder it is going to be for it to hold on to its prey,” says Kory Evans, a fish ecologist at University of Houston. “So having the ability to shed teeth and replace them is pretty important.” To be the five-foot, eighty-pound predator, “all your teeth need to be on point,” adds Dr. Evans.


The authors of the study used a unique dyeing method (detailed in the New York Times) to figure out the amount of new lingcod teeth, and the rate at which they are generated. Interestingly, the replaced teeth were “predetermined,” meaning teeth “of the same type that do not grow over time.” Most of the regenerating teeth were located in the back of the mouth, where “most of the chomping and crushing takes place.”


The gumboot chitoon, a.k.a. "The Wandering Meatloaf"


Gumboot Chiton

In other fish tooth news, scientists recently peered in on the teeth of the gumboot chiton, a mollusk of the Pacific coast. The chiton is more affectionately known as the “wandering meatloaf.” That’s because, well, it looks like a meatloaf that wanders along the shoreline, scraping algae from rocks with its (literally) ironclad teeth.


“Iron is physiologically a rare material,” said Northwestern University scientist Derk Joester, which is why Joester and fellow researchers were surprised to find in chiton teeth an iron-based mineral called santabarbaraite. The rare mineral had only ever been found in rock.


The researchers specifically focused on the stylus—a tube-like structure that fastens the teeth to the radula (a “ribbon-like tongue”). They found that santabarbaraite was unevenly distributed along the tube: more near the surface of the tooth, and less where tooth meets tongue.


The result is an incredibly stiff, yet still pliable material. Perfect for scraping food off of rocks.


The researchers think that the discovery has implications for 3-D printing, specifically in the soft robotics field. In theory, engineers would have the ability to create structures that are hard in some places, and soft in others, all “on the fly.”


Further proof (not that we needed it) that the study of all anatomy is endless—and fascinating.

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