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New tree-frog genus offers hope of uncovering many more amphibian species in India

Hindustan Times, New Delhi | ByJayashree Nandi
Dec 07, 2020 07:53 AM IST

The identification of this new genus has created ripples in amphibian research and highlighted so much that is left to be discovered in the amphibian world. The research work was carried out by SD Biju, professor and researcher, Delhi University, along with a team of researchers from the Zoological Survey of India–Andaman and Nicobar Regional Centre, National Centre for Cell Science and scientists from Indonesia, China and Thailand.

Last month, a study led by Delhi University’s department of environmental studies described a new genus of an old-world tree frog called Rohanixalus from the Andaman Islands, named after the Sri Lankan taxonomist Rohan Pethiyagoda.

Frogs of the new genus have a 2-3cm long body.(Courtsey: SD Biju)
Frogs of the new genus have a 2-3cm long body.(Courtsey: SD Biju)

Frogs of the new genus have a small and slender body ( about 2 to 3 cm long), a pair of contrastingly coloured lateral lines on either side, brown specks scattered throughout the upper body, and lay light green coloured eggs in arboreal bubble nests.

Among their many interesting behavioural traits are remarkable maternal care—the mother attends to the egg clutches until hatching and assists in the release of the tadpoles into water.

The identification of this new genus has created ripples in amphibian research and highlighted so much that is left to be discovered in the amphibian world. The research work was carried out by SD Biju, professor and researcher, Delhi University, along with a team of researchers from the Zoological Survey of India–Andaman and Nicobar Regional Centre, National Centre for Cell Science and scientists from Indonesia, China and Thailand.

Frogs are among most fascinating creatures because of their distinct croaks; their ability to camouflage, long leaps—more than 20 times their body length for some species; their bulging eyes and diversity in skin colour, texture and size. Most importantly, frogs are bio-indicators which essentially means they are extremely sensitive to pollution. Their abundance or decline can easily tell you if a wetland or water body is polluted or clean. Almost every child has a memory of following frogs in the monsoon, but such interactions are on the decline especially in urban areas because the number and diversity of frogs face a grave threat from habitat loss.

Based on an assessment by the International Union for Conservation of Nature (IUCN)t, among frogs and toads, 20 are critically endangered; 35 are endangered and 22 vulnerable. Over 260 species (includes all species) are either not evaluated or in data-deficient status according to Gururaja KV, adjunct scientist at the Gubbi Labs.

“This also indicates that for a majority of species we do not have any precise data on population size. And in the last 20 years, we have added over 200 new species to India’s list, which is about 40% of the total species in India,” he said.

Other estimates suggest that one in every three amphibian species is facing extinction with habitat loss being the primary risk to their existence. “All over the world, amphibians (frogs, salamanders and caecilians) are the most threatened group of vertebrates. One-third of all known amphibian species, or in other words one in every three species, are facing extinction threats. Yes, among the known threats, habitat loss is one of the major causes for amphibian decline worldwide. Other significant threats include climate change, chytrid fungus, and pollution,” said Biju.

Interestingly, despite the steep decline in their numbers and diversity, science is bringing to light fascinating new species of frogs every year in India. Over the last two years, a frog subfamily, many frog genera, and species have been discovered across many landscapes of the Western Ghats, which is a biodiversity hotspot on the Chota Nagpur Plateau, lowlands of the Andaman Islands and the Naga-Chin hills in the northeast.

“Last year, researchers discovered a new burrowing frog species, Sphaerotheca magadha, from a semi-urban agricultural habitat in Chota Nagpur Plateau. There was also the discovery of a new ancient subfamily, the starry frog (Astrobatrachinae: Astrobatrachus kurichiyana) from high elevation forests in the Kurichiyar hill range in the Western Ghats…Interestingly, there was also a new genus: the mysterious narrow-mouthed frog (Mysticellus franki) discovered in a road-side puddle from Camel’s Hump, a few km from the previous ancient frog. This year, researchers reported the discovery of an old lineage: Muduga leaping frog (Walkerana muduga) from the high elevation of Elivalmalai mountain north of Palghat Gap in the Western Ghats,” said Vijaykumar SP ecologist from Indian Institute of Science.

The most fascinating frogs according to Vijaykumar SP:

• The spectacular radiation (a group of frogs that share a common ancestor) of bush frogs (Rhacophoridae) that reach their highest diversity in the Western Ghats (>60 species).

• Most of them are tiny and can sit comfortably on your fingertips. These frogs are unique in having a direct mode of development: i.e they have bypassed the tadpole stage that is typical of most frogs. They carry a fascinating history of the mountains, towering rainforests, and sprawling grasslands that they call home.

• Another group that excites me is the ancient family Micrixalidae with some 24 species. Unlike other frogs, they are diurnal (active during day time), occur in the forest streams, and interestingly, they do tap dancing on rocks and leg waving, revealing a flash color on their webbed foot, to wade of intruders and attract females.

• This one is a biogeographer’s delight--The awesome ancient family, Nasikabatrachidae, is 65 million years old and whose relatives live in Seychelles Island in the Indian Ocean.

• Another fascinating frog is the ancient sub-family, the Starry frog (Astrobatrachinae) with a single species. It is very mysterious to me because we know very little of this secretive species of the forest floor.

Malabar Tree Toad (Gururaja KV)
Malabar Tree Toad (Gururaja KV)

Experience of discovering a new frog species:

Vijaykumar SP:

It was one cold night in October 2009. I and my field assistant Mayavan were on an expedition in search of frog species in the high elevations (>2000 m) on the Nilgiri plateau in the Western Ghats mountains. We were anxiously searching to locate an unknown call (each frog species has a unique call), a series of metallic tik. I was also trying to record the call with a digital recorder. The grass clumps were dense and I was trying to localize, based on the signal that we receive through a long shot-gun microphone. At one point as we looking up, we were shocked to see a herd of bison watching us, a few hundred meters away from us. Mayavan and I looked at each other, and we had to make a decision! Abandon the search? Both of us took a crazy decision, we waved and rushed towards the herd. Luckily – maybe that long shotgun microphone in the hand - the bisons turned back, slowly vanishing into the thick mist. Our risk paid-off after an hour of search, when we finally located a tiny frog, that elusive caller. We have never seen anything like that before: another new species, endemic to the high elevation grasslands of Nilgiri Plateau in the Western Ghats.

KV Gururaja:

Most exciting experience is that of Karaavali skittering frog from the coastal regions of Karnataka. This discovery also highlights citizen involvement and their contribution. The story goes back to 2015, when Mr CR Naik, officer at Kali Tiger Reserve first saw and recorded the call of this species. The call is that of white-throated kingfisher. At first, we all joked and made fun of the call record. But eventually when CR Naik showed the frog, it was new. Based on molecular work by Dr Priti Hebbar; bioacoustics work by Dr Seshadri, we finally took an integrated approach of morphology, molecular work and bioacoustics to describe the species as new with CR Naik as co-author of the species. This discovery will remain as an example of citizen science and collaborative research.

Kumbara Night Frog (Gururaja KV)
Kumbara Night Frog (Gururaja KV)

SD Biju:

New discoveries are always exciting. At the same time, they involve several challenges, especially in field-based wildlife research. My team and I have so far discovered over 100 new species of amphibians from India and neighbouring countries. Although many discoveries are accidental, such findings were possible only through sheer hard work and determination to carry out dedicated field studies and extensive documentation of Indian amphibians over 30 years! It has been a very rewarding and enjoyable journey. There are so many memorable experiences and every discovery has a story. That would make at least a hundred stories, so maybe another time.

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