Darwin's frog

Seahorses are well-known for their unconventional approach to breeding. Famously, the males are the ones that become pregnant, carrying the fertilised eggs in a brood pouch on their bellies until the fully developed young are ready to be born. This level of paternal responsibility is extremely rare in the animal kingdom. In fact, other than seahorses and their close relatives, the only vertebrate species in which the male effectively becomes pregnant is a tiny amphibian from South America called Darwin’s frog.