TEETH are typically the hardest material in the body, but not so for some suckermouth catfish (Loricariidae). Their pearly whites do something wholly untoothy: bend.
Adaptations to avoid broken or chipped teeth are common enough - the teeth of sharks and rays, for example, are slightly loose. But this is the first published report of bendable teeth. It makes sense for catfish to have them, though, since they scrape food off rocks and other hard surfaces with their mouths - a habit that could easily break rigid teeth.
Tom Geerinckx, an evolutionary morphologist at Ghent University in Belgium, extracted teeth from five species of scraping suckermouth catfish and analysed their composition and microstructure. He found that each tooth had a bendable section containing more collagen and significantly less calcium, phosphate and magnesium than the rest of the tooth. The work will appear in Physiological and Biochemical Zoology.
"[The] teeth are very long and skinny and they have a built-in section that's flexible. That's absolutely mind-blowing," says Peter Wainwright of the University of California, Davis.
Such teeth may not be unique, though. Wainwright suggests they are also found in some common reef fish that feed by scraping rocks. "I've personally tweaked their teeth and holy cow, they're bendable," he says.