Sunday, April 3, 2011

Eggs & Tadpoles of the Indian Brown Frog

The Indian Brown Frog, Indirana semipalmata. 
Photo Credit: 
L. Shyamal
A metamorphosing Indirana semipalmata.
 Photo Credit: L. Shyamal
Indirana is a genus of about 11 species endemic to the Western Ghats of southern India that usually breed in the splash zone of streams, the tadpoles are semi-terrestrial, using water that condenses on leaf litter, rocks, soil and other surfaces. They have been placed in the families Ranidae and Ranixalidae. Indirana semipalmata inhabits Tamil Nadu and Kerala in southern India and by all accounts it is relatively common and widespread at elevations between 200 and 1,100 meters above sea level. The adults are terrestrial in the leaf-litter of tropical forests and swamps and it has been recorded in coffee plantations and secondary forest. Ben Tapley of Wildlife.com is reporting that in July of 2010 an amphibian ecology study at the Agumbe Rainforest Research Station (ARRS) in Karnataka, India (http://www.agumberainforest.com/) found several egg clutches and tadpoles of this frog that were laid on the bark of a tree. Tadpoles from another clutch were observed feeding on the bark of the same tree. Three clutches of  Indirana semipalmata eggs were at least 3 m away from any standing water, and they suggest this is the first recorded case of tadpoles feeding on a bark substrate and subsequently metamorphosing on the bark of a tree. Tapley suggests this may be a localised phenomenon as Agumbe has the second highest annual rainfall in India and therefore these semi terrestrial tadpoles do not desiccate. Living in Agumbe during the monsoon was literally like living in a cloud. However, since these frogs have evolved in this environment, it would seem likely that this is their life style, and it raises the question of exactly what are the tads eating? Are they actually eating the bark or, more likely in my opinion algae, fungi, or other protists growing on the tree's surface? Also, because of the habitat difference - laying eggs on trees, instead of stream side rocks reported for other populations, it suggests this population could be a different species.

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