These Froggies Went A Courtin' And Gave Birth To Live Tadpoles
When Jim McGuire and some colleagues recently cut open a frog that they'd collected and euthanized on an Indonesian island, they got quite a shock.
"Out came the tadpoles, and they were alive!" recalls McGuire, a herpetologist at the University of California, Berkeley.
The researchers had just found the first frog known to give birth to live tadpoles.
For most frog species — more than 6,000 of them — life starts in water. A female frog lays some eggs, a male fertilizes them, and later the eggs become tadpoles that grow up into new frogs.
McGuire says finding live tadpoles inside the frog was exciting and a little creepy.
"It was very reminiscent of the scene in Alien where the little monster explodes out of the stomach of the poor human who has been impregnated with that larval alien," says McGuire.
This species of fanged frog lives on Sulawesi island and was first discovered by Indonesian researcher Djoko Iskandar. He and Ben Evans of McMaster University in Ontario, Canada, along with McGuire, describe the frog's unusual form of reproduction this week in the journal PLOS ONE.
Some other frogs reproduce in bizarre ways. For example, a couple of extinct frogs would swallow fertilized eggs and use their stomachs as breeding chambers, then give birth out of their mouths. Other frogs have special pouches on their backs to carry eggs. And some frogs in Africa give birth to little froglets that never go through a tadpole stage.
McGuire suspects the live-tadpole birth may be a way to keep predators from having a frog-egg lunch. "This is another pretty crazy reproductive mode that's evolved within frogs," he says. "Frog biologists are turned on by that sort of thing."
LOURDES GARCIA-NAVARRO, HOST:
And now let's talk frogs. The life of a frog usually starts in water. A female lays eggs. A male fertilizes them. They become tiny tadpoles. Tadpoles grow into frogs. But there's one frog species that takes a radically different approach to reproduction as scientists recently discovered. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE, BYLINE: As a kid growing up in Southern California, Jim McGuire dreamed of a career studying reptiles and amphibians. He collected his first snake at age five. Not too many frogs lived nearby, but he managed to find them.
JIM MCGUIRE: There was a place near the railroad tracks, and there were Pacific tree frogs there. And I collected some of those, including their tadpoles, and brought them home. I don't even remember what happened to them to be honest, but whatever happened to them probably was not good.
GREENFIELDBOYCE: Now he's a researcher at the University of California, Berkeley, who does his frog collecting in the rainforests of Southeast Asia. Not too long ago, on an Indonesian island, he and some colleagues euthanized one frog to dissect it. When they cut it open, they got a shock.
MCGUIRE: Out came the tadpoles, and they were alive.
GREENFIELDBOYCE: He says the shimmery, quivering tadpoles looked creepy.
MCGUIRE: I mean, it was very reminiscent of the scene in "Alien" where the little monster, you know, explodes out of the stomach of the poor human who's been impregnated with that larval alien.
GREENFIELDBOYCE: The scientists described their find in the journal "PLOS ONE." McGuire says some other frogs do bizarre things to reproduce. A couple of extinct frogs would swallow fertilized eggs and use their stomach as a breeding chamber, then give birth out of their mouths. Other frogs have special pouches on their backs to carry eggs. But McGuire says this is the first frog known to give birth to live tadpoles.
MCGUIRE: This is, you know, another pretty crazy reproductive mode that's evolved within frogs. And so, you know, frog biologists are turned on by that sort of thing.
GREENFIELDBOYCE: It's the kind of discovery even a kid might think was cool. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.