Newly Discovered Starry Dwarf Frogs Are Lone Species of an Ancient Lineage

The newly discovered ‘oddball frog’ species dwells in India’s Western Ghats, one of the hottest of the biodiversity hotspots

Astrobatrachus kurichiyana, also known as the "starry dwarf frog," has only been found on a single hill range in India's Western Ghats. Seenapuram Palaniswamy Vijayakumar

In 2010, a group of scientists embarked on a large-scale survey of amphibians and reptiles living among the Western Ghats, a forested mountain range that stretches for nearly 1,000 miles across India and teems with biodiversity. While exploring an isolated hill range one night, the team spotted a tiny frog, no bigger than a human thumbnail, scurrying about in dead leaves on the ground. It had an orange belly and bluish dots speckling its brown back—like stars lighting up a dark sky.

Writing in the journal Peer J, the researchers reveal not only that the frog is a new species, but also that it is the sole extant member of an ancient lineage. David Blackburn, study co-author and associate curator of herpetology at the Florida Museum of Natural History, calls it an “oddball frog.”

“[I]t has no close sister species for maybe tens of millions of years,” he explains.

The team has dubbed the critter Astrobatrachus kurichiyana; “astrobatrachus” means “star frog” in Greek and Kurichiyarmala is the area where the species was found. As Nicola Davis reports for the Guardian, the researchers have also suggested an English name: the starry dwarf frog.

It isn’t entirely surprising that A. kurichiyana escaped notice for so long; the species is “secretive and difficult to spot,” the study authors write. A. kurichiyana is nocturnal, and when the expedition team tried to shine a flashlight on the frogs, they quickly hopped into the cover of the leaf litter. The species is also very small, measuring just two centimeters long.

The researchers managed to collect several specimens, but at the time, they weren’t convinced that there was anything particularly special about the frog, aside from its unique coloration. A. kurichiyana was just one of 30 animal species the team collected that night in the Western Ghats, and new frog species are found quite frequently in India; according to Adam Vaughan of New Scientist, the number of known frogs in the country has jumped from 200 to 400 over the past two decades. So the discovery of A. kurichiyana initially “wasn’t too exciting for me,” says Seenapuram Palaniswamy Vijayakumar, lead author of the study who is now a postdoctoral scientist at George Washington University. “I didn’t realize it would become so interesting.”

A few years later, Vijayakumar and his fellow researchers decided to take a closer look at the preserved specimens. They CT scanned the frogs, to learn more about the species’ skeleton and other internal features, and also conducted a genetic analysis. A. kurichiyana, they found, represents a new sub-family and a new genus. It is most closely related to the Nyctibatrachidae family of frogs, which dwells in the Western Ghats and in Sri Lanka, but their last common relative lived tens of millions of years ago. In all that time, says Blackburn, it is possible that A. kurichiyana has had “no close sister species.”

The discovery of the starry dwarf frog highlights the biodiversity that flourishes within the Western Ghats, a region with an important evolutionary history. India was once part of Africa; it split from Madagascar around 89 million years ago and, before it ultimately collided with mainland Asia, spent many years as an island. During this period of isolation, new life forms evolved, particularly within the Western Ghats, which are home to a number of different ecosystems, such as evergreen forests, grasslands, swamps and wildflower meadows. Today, the region is home to one-third of India’s plants, around half of its reptiles, and more than three-fourths of its amphibians. Some of these species are not found anywhere else in the world.

At this early phase, there is still much the researchers don’t know about A. kurichiyana: like the phases of its life-cycle, its conservation status and whether it is descended from ancestors in Africa or Asia. But for now, the team is celebrating the survival of a species that has persisted for millions of years in one of the world’s “hottest” biodiversity hotspots.

“These frogs are relics,” says Vijayakumar. “This lineage could have been knocked off at any point in time. Irrespective of who we are, we should be celebrating the very fact that these things exist.”

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