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 This little amphibian from the rain forests of Indonesia's island
of Sulawesi is the only one of the world's 6,455 frog species to
give direct birth to tadpoles, eschewing the common froggy practice
of laying eggs, scientists said on Wednesday.
"Reproduction in most frogs could not be more different from human
reproduction. In this case, what is most interesting, ironically, is
that the reproductive mode is more similar to our own," said
herpetologist Jimmy McGuire of the University of California,
Berkeley, whose research appears in the scientific journal PLOS ONE.
This frog, usually gray or brown, measures about 1-1/2 inches long
(40 mm), weighs less than two-tenths of an ounce (5 grams) and
belongs to the Asian group of fanged frogs. Males possess two
fang-like projections from the lower jaw that are used in fighting.
 The frog lives along small streams and puddles in rainforest
habitats, doing its best to avoid being eaten by larger fanged frog
species as well as snakes and frog-munching birds.
Its mode of reproduction sets this frog apart.
"The vast, vast majority of frogs have external fertilization. For
mating, the male grips the female around the waist and releases
sperm as she releases her eggs," McGuire said.
Those eggs mature through stages including the aquatic tadpole
larval phase, typically limbless with a tail that propels it through
the water.
About a dozen frog species rely on internal fertilization, McGuire
said. All but the newly identified one either deposit fertilized
eggs or give birth to froglets, essentially miniature versions of an
adult that already passed through a modified tadpole stage while
still in an egg capsule inside the female.
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The female Limnonectes larvaepartus (meaning "marsh swimmer that
gives birth to larvae") instead gives birth to tadpoles.
"It's totally unclear why this mode of reproduction has not evolved
more frequently," McGuire said.
"My favorite topic when it comes to frog evolution and
diversification is the bewildering variation in reproductive modes
that occur. Frogs exhibit all sorts of interesting twists."
There have been frogs that swallowed their eggs and brooded them in
the stomach, a species in which the male broods the eggs in his
vocal sac, and many species that carry eggs and tadpoles in pouches
on their backs and sides, he said.
(Reporting by Will Dunham; Editing by Mohammad Zargham)
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