The discovery of an unknown species of frog in India is less surprising than the fact that it was discovered at all.
The starry dwarf frog is extremely small, maxing out at the size of your thumb-nail. It is extremely well camouflaged, looking exactly like leaf litter with legs. It is extremely rare and reclusive and hates to be observed. Basically the thing is invisible, but there you are. It has been found.
Actually, Astrobatrachus kurichiyana seems to be the only survivor in a previously unknown branch on the frog evolutionary tree of life, say the herpetologists from the Indian Institute of Science, the George Washington University, the Zoological Survey of India and of course the Florida Museum of Natural History, who wrote the study published in the life and environmental sciences journal PeerJ on Tuesday.
Its back is dark brown, which is very much the color of rotting leaves. Its tummy is bright orange, but then it doesn’t hop around belly-up; and it’s speckled with pale blue dots, hence the cosmological reference in its name. The dots resemble mold on decaying leaves.
The effectively invisible frog was noticed despite itself in the so-called Benevolent Mountains, or the Western Ghats, which is a vast mountain range that runs all along the western Indian coast, from Gujarat down 1,600 kilometers (about 990 miles) to India’s southern tip.
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For all that wildlife has been suffering badly in the supremely crowded Indian subcontinent, the Ghats are still considered to be a “diversity hotspot,” albeit one losing its hallmark diversity together with its forest cover.
The region’s extraordinary fauna stem from its tectonic history. “India, once part of Africa, split from Madagascar about 89 million years ago and drifted northeast, eventually colliding with the Asian mainland and giving rise to the Himalayas,” explains the team. But for eons, before it joined with Asia, India was an island. Its protracted isolation led to the evolution of new life forms, and may have protected species that had disappeared elsewhere, like our starry frog.
Astrobatrachus kurichiyana is named for its constellation-like markings and the indigenous people of Kurichiyarmala, the specific range of hills where it was belatedly noticed.
“The starry dwarf frog is an expert hider. Plunging into leaf litter at the slightest disturbance, it has successfully evaded attention for millions of years - until now,” wriggle the researchers, headed by Seenapuram Palaniswamy Vijayakumar.
David Blackburn of the Florida museum suspects this “oddball frog” hasn’t had a sister species for “maybe tens of millions of years,” though who knows, maybe there’s another effectively invisible frog sitting right next to it. In other words, it’s a sort of living fossil.
“The coloration was the first thing that stood out to me, these starry patterns with a blue tinge,” said Vijayakumar, now a postdoc at George Washington University.
“These frogs are relics. They persisted so long. This lineage could have been knocked off at any point in time,” Vijayakumar said. “Irrespective of who we are, we should be celebrating the very fact that these things exist.”
Happily for biodiversity, the team found numerous unknown species beyond the starry dwarf frog in the Ghats. And they only noticed it because they were staring at the ground looking for leeches, as people do. And then they realized they’d caught one just like it the night before… and that it was unknown.
That was actually some years ago but the animal’s classification took time. The team, with the help of the Florida museum's scientists, found that A. kurichiyana’s closest relatives are the family Nyctibatrachidae, a group of nearly 30 Asian frog species – but their last common ancestor could date back tens of millions of years. Or it could be sitting right there.
One question Vijayakumar and Blackburn are interested in exploring further is whether India’s frogs descended from even older African amphibia, or whether they originated in Asia itself and moved south to the subcontinent.
The bottom line is that all the scientists know about the starry dwarf frog is that it exists. The researchers admit they know nothing of its life cycle, the sound of its call or whether the species is threatened or endangered - but they sure are hard to find.
Upon the return of his study co-author, K.P. Dinesh of the Zoological Society of India, to the hill range where the frog was first found, Vijayakumar said that Dinesh searched the whole forest floor and hardly saw any frogs. "This frog is so secretive. Just one hop into the litter, and it’s gone.”