Tiny frog - the world’s smallest vertebrate
A frog that can perch on the tip of your pinkie with room to spare
has been claimed as the world’s smallest vertebrate species,
‘out-tinying’ a fish that got the title in 2006. But the discoverer of
another weensy fish disputes the claim.
A tempest in a thimble, some might say.
An article in the journal PLoS One named Paedophryne amauensis as the
world’s smallest animal with a spine.
The adult frogs are about three-tenths of an inch long, and a
millimetre or so smaller than a carp found on the Indonesian island of
Sumatra.
The frogs are so small that Louisiana State University herpetologist
and environmental biologist Christopher Austin had to enlarge close-up
photos to describe them.
But the males of a species of deep-sea anglerfish are about two mm
smaller, said University of Washington ichthyologist Theodore Pietsch,
who described them in 2006.
The males don’t have stomachs and live as parasites on 1.8-inch
(4.57-centimetre)-long females.
Austin discovered the tiny frogs - along with another small frog
species - in August 2009 while on a trip to Papua New Guinea to study
the extreme diversity of the island’s wildlife.
He said he knew about the anglerfish but felt that average species
size made more sense for comparison.
Steven J. Beaupre, a University of Arkansas scientist and
president-elect of the American Society of Ichthyologists and
Herpetologists, said many vertebrates have males and females of very
different sizes, “so it is reasonable that the world’s smallest
vertebrate may end up being either the males or the females of some
specific fish or amphibian species.”
He said he doesn’t pay attention to “tiniest” reports, but the frogs
themselves are a significant discovery.
“The discovery of two new frog species comes as great news against
the background of more prevalent accounts of tropical amphibian
extinction,” he wrote in an email.Knowing about such tiny creatures and
their ecology, he said, helps scientists “better understand the
advantages and disadvantages of extreme small size and how such extremes
evolve.
Fundamentally, these tiny vertebrates provide a window on the
principles that constrain animal design.”
Austin said that since these frogs hatch out as hoppers rather than
tadpoles and live on the ground, their existence contradicts the
hypothesis that evolution at large and small extremes is linked to life
in water.
At least 29 species of minuscule frogs in equatorial regions
worldwide live in leaf litter or moss that is moist year-round and eat
even tinier invertebrates, creating a previously unknown “ecological
guild” of similar animals with similar life habits, he said.“We realised
these frogs were probably doing something incredibly different from what
normal frogs do - invading this open niche of wet leaf litter that is
full of really tiny insects that other frogs and possibly other
creatures weren’t eating,” Austin said.
In August 2009, Austin and graduate student Eric Rittmeyer were
collecting and recording the mating calls of frogs at night in a
tropical forest near the village of Amau in eastern Papua New Guinea,
when they heard a chorus of high-pitched “tinks.”
“This frog has a call that doesn’t sound like a frog at all. It
sounds like an insect,” he said. The calls seemed to surround them, and
it took a while to be sure they were coming from the ground.
Since they couldn’t locate the noise-maker, they snatched up some
habitat, expecting to find a six-legger in it.
“We found it by grabbing a whole handful of leaf litter and putting
it into a clear plastic bag and very, very slowly going through that
litter leaf by leaf by leaf until we saw that small frog hop off one of
those leaves,” he said.Getting photos took some effort - the frogs can
leap 30 times their own length. After hopping around for a bit, they
settled down long enough for a close-up or two, Austin said.
Their expedition, sponsored by the National Science Foundation, later
turned up another new species of tiny frog, found farther west along the
island’s coast.
The other is closely related, but a millimetre or so larger, and it
had a different call.
Austin estimated that they found 20 previously unknown species in New
Guinea, which is such a hotspot of diversity that scientists figure
they’ve described only about six-tenths of all the species living there.
Maurice Kottelat, a Swiss scientist who found the tiny carp called
Paedocypris progenetica, wrote in an email that it’s hard to compare
frogs and fish, because they’re measured differently: frogs from
nose-tip to the excretory vent, and fish from nose to tail.
- AP
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