Sandtadpoles

Tadpoles of the monotypic Indian dancing frog family Micrixalidae have remained obscure for over 125 years. Here we report the discovery of the elusive tadpoles of Micrixalus herrei from the sand beds of a forested stream in southern Western Ghats, and confirm their identity through DNA barcoding.

A group of Indian scientists discovered the tadpoles in the Western Ghats, a mountain range in southern India known as a biodiversity hotspot. They found them by digging in the sandy bottoms of streams. These tadpoles spend all their time underground consuming sand and bits of organic matter. After several months, they develop into adult Kallar dancing frogs (Micrixalus herrei), colorful frogs well known for waving their legs during mating displays.

The adult frog bears almost no resemblance to the tadpole form. Actually, the morphological differences were so great that the researchers had to use DNA barcoding to demonstrate that tadpoles and adults were one and the same species.

The tadpoles show some very interesting adaptation to life in the sand such as skin-covered eyes, a powerful tail for propelling them through sediment, and ribs, which haven’t been observed in other burrowing frogs. They also possess specialized mouthparts that act as a filter to prevent large sand particles from entering the mouth.

The documentation of Micrixalus herrei larval habitat informs decisions relating to their conservation and management. For instance, their association with forest cover, perennial streams, and sandy banks reveals specific habitat requirements for this species and potentially other threatened Micrixalus (e.g., M. gadgili and M. kottigeharensis). These tadpoles are also likely obligate burrowers that breed during low-water periods. This habitat and breeding information provides a basis for comparison with other Micrixalus species, most of which were only recently described.