Frogs Found Giving Birth to Tadpoles

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Scientists recently found that a small, little-known Indonesian frog gives birth to tadpoles rather than laying eggs. The recently described Limnonectes larvaepartus is the only frog species known to give birth to live young, a reproductive method typically relegated to mammals, reports Live Science.

The tiny Limnonectes larvaepartus—which weighs about as much as a nickel—is a fanged frog, discovered in 1998 by zoologist Djoko Iskandar at the Bandung Institute of Technology. When Iskandar and his team first discovered the frog, says Iskandar, the researchers suspected it might be giving birth to tadpoles, but not enough was known about the species at the time to prove such a novel finding. The frog had never been observed mating or giving birth.

Much more information about fanged frogs is now available to researchers regarding their coloration, webbing and texture, making findings far easier to prove and distinct species far easier to classify. So when herpetologist Jim Mcguire picked up a pregnant fanged frog in the Indonesian island of Sulawesi last summer and it immediately gave birth to tadpoles in his hand, Mcguire was able to conclude that the early assumptions of Iskandar and his team were correct. It wasn’t until molecular data could be utilized that scientists could begin to sort the various species, says Mcguire.

The vast majority of the 6,000 known species of frog lays eggs and fertilizes them externally, though about a dozen species of frog fertilize eggs internally, some of them give birth to fertilized eggs while the others give birth to live froglets. Fanged frogs get their name from two projections protruding from the lower jaw, which are used for fighting. The Limnonectes larvaepartus—recently described in a study in PLOS One—is still the only fanged frog known to give birth to live tadpoles, however.

Only three fanged frog species are recognized from Sulawesi, but at least 15 are thought to live on the island, says the study. It is still unclear exactly how the male of the Limnonectes larvaepartus species manages to fertilize the eggs while they are still inside the female, considering the male has no conventional sperm-delivering sexual organs, reports Tech Times.

Much is still unknown about internal fertilization among frogs, but at least two species of frog have “tails,” penis-like organs which deliver sperm to the eggs inside the female tailed frogs. The female then lays the fertilized eggs under rocks in streams where they later hatch. Other species with internal fertilization give birth to tiny young frogs known as froglets, but only the Limnonectes larvaepartus is known to have internal fertilization and give birth to tadpoles.

The species typically gives birth away from streams in small pools, possibly to avoid other, larger frogs. There is some evidence to suggest the male of the species may guard its young, but there is not enough research yet to prove that theory. According to Ben Tapley with the Zoological Society of London, it is not rare to find a new species, but it is very rare to discover a new mode of reproduction.

By Sree Aatmaa Khalsa

Live Science
The New York Times
Tech Times
Photo by: Riccardo Palazzani – Flickr License

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