Teething helps piranhas eat everything

The researchers found that piranhas always store their teeth under their existing teeth to replace them when they are dull.

Piranhas are used to chew bones and tear flesh. Like kitchen knives, their teeth get blunt with time. Because there is no way to sharpen teeth, piranhas lose all their teeth on one side of their jaws and regrow teeth several times in their lifetime.

Scanned images of red-bellied piranhas.(Photo: CNN).

The new analysis of piranha's fish teeth reveals new rows of teeth in a small cavity beneath the current teeth, so the fish never lacks teeth. They can sustain chewing every part from scales, gills, meat to the whole prey. The research is published in the journal Evolution and Development.

Previous research has shown that piranhas lose one row of teeth at a time and develop new sharp teeth. But scientists did not find any piranhas that lost their teeth.

"The teeth form a contiguous row and fall out at the same time on one side of the jaw. The new teeth gradually wear old teeth until they are ready to erupt. Therefore, piranhas never rinse their teeth even though they are constantly changing their teeth." Explains Adam Summers, head of research, professor of biology and fisheries science at the Friday Harbor Laboratories experimental station on the island of San Juan.

The team used new imaging technology on fish samples in many museums, 3D tests and analyzed 40 different species. As a result, they were able to observe the waiting teeth below the current teeth in the jaw.

The detailed review also helps scientists understand why piranhas replace their teeth. The rows of teeth on each side of the jaw act as self-assembling blocks, which helps them reduce the pressure when chewing.

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