When it comes to parenting, some animals will go the extra mile. Possums, for example, have their young clinging on as they trundle around. Kangaroos give birth to immature young that they keep in a pouch until it’s bursting at the seams. Humans let 30 year old offspring move back in.
And fish? Do mouth brooding.
(A mouthful! Source)
The fish above has a mouthful of eggs. It’s a cichlid. And some species of cichlid will go the extra…mouthful to protect their eggs. They are so worried about the predation of their eggs that the females lay eggs, circle around, and then immediately gobble them up, holding them in their mouths until the fry hatch, and often even longer, until they are big enough to make it on their own.
However, it turns out that the female fish are in such a rush to pick up their eggs, they sometimes don’t even give them time to get fertilized! Holding a mouth of unfertilized eggs seems like kind of a waste. But the males have figured out not just how to get fertilization to happen…they got some oral sex out of the bargain.
Mrowka, W. “Oral Fertilization in a Mouthbrooding Cichlid Fish” Ethology, 1987.