The piranha fish are known for their sharp teeth that they use to tear the flesh of their prey, or scrape plants off of rocks.

Piranhas Constantly Regrow All Teeth On One Side Of Their Mouth At Once

These teeth are also remarkable. Scientists discovered that piranhas lose all of their teeth on one side of the mouth at once and regrow them.

It was thought that this happens to replace the dulled teeth with brand new ones. Unfortunately, there is no documentation or museum specimen that can back up these theories. Researchers, however, were able to get a closer look at the piranha teeth using new imaging technology.

In a study published in the journal Evolution & Development, a team of researchers were able to confirm that piranhas, as well as their plant-eating relative pacus, do lose and regrow all the teeth on one side of their mouth multiple times throughout their lives.

The contours and topography of the teeth inside different fish specimens revealed that the teeth on each side of the mouth are interlocked together, forming two strong blocks in the mouth.

This explains why the fish regrow their teeth on either side all at once.

"Once you link teeth together, if one wears too much, it becomes like a missing link in an assembly line. They all have to work together in a coordinated way," said study researcher Matthew Kolmann, from George Washington University.

The interlocking of the teeth is believed to be beneficial to the fish, since this allows them to distribute stress over all of their teeth when they crack a nut or tear cut through flesh.

"We propose that interlocking mechanisms prevent tooth loss and ensure continued functionality of the feeding apparatus," the researchers wrote in their study, which was published on Aug. 26.

Never Toothless

The piranhas are also never toothless regardless that they constantly replace their teeth. Study researcher Adam Summers, from UW Friday Harbor Laboratories on San Juan Island, explained that the new teeth wear the old ones like hats until the old ones are ready to erupt.