frog gives birth to tadpoles
The newly described frog L. larvaepartus is the only frog known that gives direct birth to tadpolesJim McGuire photos

A frog that gives birth to live tadpoles has been discovered in the rainforests of Indonesia's Sulawesi Island.

Named Limnonectes larvaepartus, the species is the first found that gives birth to live young rather than laying eggs.

While the species of frog was discovered a few decades ago and was believed to have given birth to live tadpoles, proof has remained elusive until now.

Published in the journal PLOS One, scientist at the University of Ontario were working in the rainforests when they came across what they thought was a male frog. Herpetologist Jim McGuire soon found himself holding not only one frog buy a dozen newborn tadpoles.

"Almost all frogs in the world – more than 6,000 species – have external fertilisation, where the male grips the female in amplexus and releases sperm as the eggs are released by the female," he said.

frog gives birth to tadpoles
Two tadpoles, each about 10 millimeters long, shortly after birthJim McGuire, UC Berkeley

"But there are lots of weird modifications to this standard mode of mating. This new frog is one of only 10 or 12 species that has evolved internal fertilisation, and of those, it is the only one that gives birth to tadpoles as opposed to froglets or laying fertilised eggs."

Normally, male frogs fertilise eggs after the female lays them. In about 12 species the female frog has evolved to fertilise the egg inside its body, which normally results in froglets – little replicas of the adults.

In Limnonectes larvaepartus, the frog gives birth to tadpoles in small pools located away from streams. There is also evidence that the males guard the tadpoles.

McGuire, who first encountered the species in 1998, said Sulawesi extremely diverse island for fauna, having formed from the merging of several islands about eight million yearas ago.

"Sulawesi is an incredible place from the standpoint of species diversity endemic to the island as well as in situ diversification," he said.