Piranhas and their plant-eating relatives, pacus, replace rows of teeth all at once
Not losing teeth individually might help distribute wear and tear from the fishes’ diets more evenly
Rows of well-developed teeth lurk in the jaw, ready to replace ones already in use on one side of a red-bellied piranha’s (Pygocentrus nattereri) mouth, as seen in these views of a museum specimen.
M. Kolmann/GWU