There's no shame in having problems in the bedroom, but “sorry, my front teeth aren't growing” might be something new.
Male ratfish, also called ghost sharks, live in the depths of the northeastern Pacific Ocean and have bulging green eyes, venomous spines and plate-like teeth that they use to crush the shells of shellfish and crabs.
Inside the pocket above their eyes they also have a fleshy rod, somewhat similar to the dorsal fin of an angler fish, covered in spines.
Now researchers have discovered that they are actually teeth with mineralized tips.
However, those jaws aren't used for eating – the appendage, called a flail, is designed to grip the female's pectoral fin during mating, new research has found.
Carly Cohen, a researcher at the University of Washington's Friday Harbor Lab who collaborated with the team, said scientists had never before been able to detect teeth outside the mouth in this way.
She said: “This crazy, absolutely fascinating feature overturns the long-standing assumption of evolutionary biology that teeth are an exclusively oral structure.”
“The tenaculum is a developmental relic rather than a strange isolated feature, and the first clear example of a toothed structure outside the jaw.”
Gareth Fraser, a professor of biology at the University of Florida and senior author of the study, added: “If these strange chimeras have teeth sticking out on the front of their heads, it makes you wonder about the dynamics of dental development more generally.”
“If chimeras can form teeth outside their mouths, where else can we find teeth?”
To be clear, it should be noted that Fraser does not believe that the ratfish is a chimera, best known as a fire-breathing monster with the head of a lion, the body of a goat, and the tail of a snake.
Chimaeras are cartilaginous fish that resemble sharks, but they lack many shark-like features, such as sharp teeth or scales.
But Fraser and his team wanted to know why ratfish actually have shark-like teeth, even though they're located on a club-like grip used for sex.
So, according to a paper published in the Proceedings of the National Academy of Sciences, the researchers studied 40 ratfish specimens, some of which grew to more than two and a half feet in length, as well as fossils.
Using micro-CT scanning, they watched as the tentacle grew over the rat's lifetime from a tiny appendage into a long rod used for love bites.
Molecular tests have identified genes in this growth that are responsible for the formation of teeth, which are commonly found in sharks' mouths.
One of the ghost shark's ancient relatives, Helodus simplex, which lived 315 million years ago, also had a tentacle-like device extending from its nose to its upper jaw.
This suggests that the tip teeth were the result of evolutionary ingenuity, or “bricolage,” says Michael Coates, a professor of biology at the University of Chicago.
“We have a combination of experimental data and paleontological evidence showing how these fish used an existing tooth production program to create a new device needed for reproduction,” he added.
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For Fraser, it's not all that surprising how this ugly, not-quite-shark-but-a-shark with a toothy appendage that it uses to snag its own kind came to be. This is the deep ocean, after all.
From fields of thin, dark red worms to alien glowing snails that have never seen the light of day, all sorts of life thrives in this dark, oppressive environment.
“There are still many surprises in the deep ocean that we have yet to uncover,” Fraser said.
Sourse: metro.co.uk
