Piranha fish are incredible animals that have gotten a bit of a bad reputation over the years. Though relatively small, the fish sport jaws lined with incredibly sharp teeth that they can use to tear flesh from bone. The fish, which are actually omnivores and not strict carnivores, don’t often mess with humans, but there’s no denying that their fearsome bite makes them a threat, especially if food is scarce.

Now, a new study published in Evolution & Development reveals that the teeth of various piranha species are even more unique than scientists first realized. The fish, it seems, are basically tiny tooth factories.

Piranha teeth are special for a few different reasons, including the fact that they are interlocked. The teeth on either side of their mouths operate like a single unit, distributing the impact of a bite across multiple points. This works well for the fish, but it also means that damage to the teeth can only be fixed by replacing an entire set at once.

Using a CT to scan some piranha specimens, the researchers discovered that this is exactly what the animals do, growing in entire rows of replacement teeth simultaneously. The quirk here is that the fish only seem to grow in these replacement teeth on one side at a time, with the top and bottom rows on one half of their “face” appearing before the growth begins on the other side.

“The teeth form a solid battery that is locked together, and they are all lost at once on one side of the face,” Adam Summers, senior author of the study, said in a statement. “The new teeth wear the old ones as ‘hats’ until they are ready to erupt. So, piranhas are never toothless even though they are constantly replacing dull teeth with brand new sharp ones.”

The good news is that piranha attacks on humans are incredibly rare, so we can admire this wild teeth-recycling ability without worrying that we’ll be the next meal.