A type of catfish lays its eggs among the eggs of another fish. The catfish babies then eat those eggs!
Growing your young inside of you until they are ready to be born is tough enough. Ask any pregnant woman.
However, the poor Cichlid fish has a lot more to deal with. The Cuckoo Catfish is a small catfish that lives in Lake Tanganyika in Africa. Like all fish, the cuckoo lays eggs but with a twist.
The cichlid fish also lives in Lake Tanganyika. It lays it's eggs and then keeps them in it's mouth before they are ready to hatch.
The cuckoo fish waits for the cichlid to lay their eggs then hastily swoops in, eats some of the cichlid eggs and lays their own eggs where the cichlid eggs are.
Distressed, the cichlid scoops up both her remaining eggs and the cuckoo eggs in her mouth. The cuckoo eggs will then hatch inside the female cichlid's mouth and eat her eggs before they are released.