Tadpoles of the Indian dancing frog; Sonali Garg and Sathyabhama Biju hunting
for the hatchlings. Picture courtesy: SD Biju
New Delhi, March 30: Indian and Sri Lankan zoologists today announced their discovery of the tadpoles of the Indian dancing frog, an amphibian known to science for about 135 years but whose hatchlings had until now remained unseen.
The scientists from the University of Delhi and Sri Lanka's University of Peradeniya found the tadpoles endowed with an eel-like appearance and muscularised body and tails living deep underground in the southern edge of the Western Ghats, 200km from Thiruvananthapuram.
The family-tree of amphibians worldwide has hitherto documented only four families of subterranean tadpoles. The burrowing tadpoles of the Indian dancing frog adds a fifth family among those known, the researchers said, describing their findings today in the research journal PLOS One.
"These tadpoles probably remained unnoticed all these decades because they live deep underground unlike most other tadpoles that live in water," Sathyabhama Das Biju, professor of zoology at the department of environmental studies, University of Delhi, told The Telegraph.
The Indian dancing frog - so called because of its unusual courtship behaviour during which the males execute an amphibian dance to attract the females - has been known since the early 1880s, but no one had ever scientifically documented the existence of its tadpoles. While most frogs croak ahead of mating, the dance ritual appears important to this species to overcome ambient forest noise.
"They're amphibians, so we knew there had to be tadpoles, only no one knew where they were," said Sonali Garg, a research scholar and co-author of the research paper. "The females of another species of frogs in the same family have been known to dig cavities in streambeds of shallow waters," she said.
During routine field studies in the Agasthyamalai Biosphere Reserve in Kerala during early 2012, the researchers observed an additional unusual facet of the courtship behaviour - after the dancing ritual, the females appeared to guide the males towards sandbeds near streams.
The scientists, wondering whether the females of this species too lay eggs underground, followed the frogs and spotted about a dozen tadpoles after digging several sites near streams.
They found the tadpoles' guts contained fine sediments and sand suggesting that the creatures eat sand. "While water-dwelling tadpoles feed on algae and tiny insects in the water, the dancing frog's tadpoles are sand-eaters, drawing nutrition from the sand," Biju said.
The scientists say their findings underscore the uniqueness of amphibians in the Western Ghats which is a key zone rich in biodiversity. The other four families of subterranean tadpoles have been reported earlier from Madagascar and sites in South America.
The Delhi scientists collaborated with biologists Gayani Senevirathne and Madhava Meegaskumbura from Peradeniya's department of molecular biology and Ryan Kerney from Gettysburg College in the US to confirm the identify the tadpoles.