If their names didn't give it away, ghost sharks are very strange creatures. A new study reveals just how strange. The fish grow teeth out of the top of their heads.
Ghost sharks are green with glowing skin and eyes and measure around two feet. Some people call them ratfish. But a new study reveals a new characteristic previously unknown. The ghost sharks have teeth growing out of their foreheads. They have an appendage called a tenaculum, which has little teeth.
Rather than be used for eating, the teeth help the males grasp onto females during mating, according to a study published in the Proceedings of the National Academy of Sciences.
Ghost Sharks
"This insane, absolutely spectacular feature flips the long-standing assumption in evolutionary biology that teeth are strictly oral structures," Karly Cohen, a researcher at the University of Washington's Friday Harbor Labs, told BBC. "The tenaculum is a developmental relic, not a bizarre one-off, and the first clear example of a toothed structure outside the jaw."
Meanwhile, Dr. Gareth Fraser and the group studied ghost sharks to confirm that they were indeed teeth.
"The rows of teeth are all organized in a very similar way in this conveyor belt of teeth that we see in sharks," Fraser, an evolutionary biologist at the University of Florida, said.
There are still a lot of questions regarding the forehead structure. But researchers can help narrow down some things. For instance, the structure shows vertebrates can grow teeth outside of an oral cavity.
"We haven't seen anything like this anywhere else in the animal kingdom, period," Fraser said.
In order to complete the study, researchers performed molar tests on the ghost sharks. They determined the structures were very similar to the teeth found inside their own mouths. Further research showed that the animals use the structures for mating purposes.
