Heterodontism; heterogeneous + Greek odus, odontos tooth. Differences in the shape and size of teeth. There are many small teeth in the mouth of the catfish. It is impossible to count them. They look more like a brush. There is even an opinion that the catfish is a toothless fish. It is a predator that always tries to swallow its prey whole because it cannot tear off pieces as it has no teeth as such.