Sand-eating tadpoles found in Western Ghats

The Hindu, March 30, 2016 
NEW DELHI,  

Adding to the burgeoning cache of frog-finds in India, researchers have discovered a sand-eating tadpole that lives in total darkness, until it fully develops into a young frog.

S.D. Biju from the University of Delhi said in a statement: “We provide the first confirmed report of the tadpoles of Indian Dancing frog family. These tadpoles probably remained unnoticed all these years because of their fossorial [underground] nature, which in itself is a rare occurrence in the amphibian world.”

The group of scientists from the University of Delhi, the University of Peradeniya, Sri Lanka and Gettysburg College, California discovered and documented the tadpole in the peer-reviewed PLOS One, an open-access journal.

The tadpole belongs to the so-called Indian Dancing Frog family, Micrixalidae. They get that name from their habit of waving their legs as a sign of territorial and sexual display while sitting on boulders in streams.

Though these kind of displays are well known, information on the tadpoles of these frogs were completely unknown, according to Dr. Biju.

In January, Dr. Biju reported in the same journal of a frog species called Frankixalus jerdonii, once considered a species lost to science.

Skin-covered eyes

The purple tadpoles were discovered from the deep recesses of streambeds in the Western Ghats and they possess muscular eel-like bodies and skin-covered eyes, which helps them to burrow through gravel beds.

Though they lack teeth, they have serrated jaw sheaths, to possibly prevent large sand grains from entering the mouth while feeding and moving through sand.

The authors posit that unlike most tadpoles that swim early on, the Micrixalidae tadpoles hang onto underwater rocks with their powerful suckering mouths. When their arms grow strong enough they dig underground, where they live most of their lives, only to emerge in forest streams to reproduce.

Other unusual features of the tadpoles were ribs and whitish globular sacs storing calcium carbonate, known as “lime sacs,” noted Madhava Meegaskumbura from the University of Peradeniya.

“Only four families of frogs are reported to have ribs, but we show that at least some of Micrixalidae also have ribs, even as tadpoles; this adaptation may provide for greater muscle attachment, helping them wriggle through sand,” he said.