Unique Sulawesi frog gives birth to tadpoles

http://www.eurekalert.org/pub_releases/2014-12/uoc--usf122914.php

Public Release: 31-Dec-2014
University of California - Berkeley

University of California, Berkeley, herpetologist Jim McGuire was slogging through the rain forests of Indonesia's Sulawesi Island one night this past summer when he grabbed what he thought was a male frog and found himself juggling not only a frog but also dozens of slippery, newborn tadpoles.

He had found what he was looking for: direct proof that the female of a new species of frog does what no other frog does. It gives birth to live tadpoles instead of laying eggs.

A member of the Asian group of fanged frogs, the new species was discovered a few decades ago by Indonesian researcher Djoko Iskandar, McGuire's colleague, and was thought to give direct birth to tadpoles, though the frog's mating and an actual birth had never been observed before.

"Almost all frogs in the world - more than 6,000 species - have external fertilization, where the male grips the female in amplexus and releases sperm as the eggs are released by the female," McGuire said. "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 fertilization, and of those, it is the only one that gives birth to tadpoles as opposed to froglets or laying fertilized eggs."

Frogs have evolved an amazing variety of reproductive methods, says McGuire, an associate professor of integrative biology and curator of herpetology at UC Berkeley's Museum of Vertebrate Zoology.

Most male frogs fertilize eggs after the female lays them. About a dozen species, including California's tailed frogs, have evolved ways to fertilize eggs inside the female's body. However, the mechanisms of internal fertilization are poorly understood in all but California's two species of tailed frogs, the latter of which have evolved a penis-like organ (the "tail") that facilitates sperm transfer. Whereas the tailed frogs deposit their fertilized eggs under rocks in streams, the other frogs previously known to have internal fertilization give birth to froglets - miniature replicas of the adults.

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