Deep-sea fish employs tooth-adorned forehead club for mate gripping during mating activities

In a groundbreaking discovery, a team led by Karly Cohen at the University of Washington has uncovered evidence suggesting a new theory for the evolution of teeth in vertebrates. The research, announced in a press release and published in the journal Proceedings of the National Academy of Sciences, reveals that the tenaculum of the spotted ratfish, a creature known for its retractable club on its forehead equipped with rows of sharp teeth, may have once been a site for tooth growth.

The tenaculum teeth of the spotted ratfish are formed from a dental lamina, the same stem-cell tissue that builds jaws full of teeth. These teeth grow in conveyor-belt rows, constantly replaced like a shark's jaw, and have pulp cavities, dentine layers, and mineralized tips, similar to regular teeth. This discovery challenges the assumption that teeth are strictly oral structures.

The fossil record supports the idea that ratfish coopted a preexisting program for manufacturing teeth to make a new device essential for reproduction. The tenaculum teeth of some females of certain species retain remnants, suggesting it may not have always been solely for reproduction. This discovery pushes back against how scientists think teeth evolved in the first place.

Dominique Didier, who studies chimaeras, suspects that the tenaculum may have begun as a defensive weapon or warning signal. The tenaculum of ratfish relatives from 315 million years ago, like Helodus simplex, was covered in whorls of teeth almost identical to their oral ones.

This research could have far-reaching implications for our understanding of tooth development and potentially lead to new ways to repair or regenerate human teeth. The team's findings are a testament to the ongoing exploration of the natural world and the surprises that lie within. The research group studying the development of teeth outside the mouth in other species is currently led by a university, but the specific name was not disclosed in the search results.

Deep-sea fish employs tooth-adorned forehead club for mate gripping during mating activities