Frogs with missing eyes, extra limbs alarm scientists

Pesticides may be behind deformed frogs in Western Ghats, and some of the banned chemicals come from Tamil Nadu.

A deformed frog in the Nilgiris. Photo : P. Santosh Kumar

The Western Ghats have been witnessing an unusual number of frogs with deformities. Scientists and public health experts are alarmed by the phenomenon, which they suspect to be symptomatic of underlying toxicity in the environment and the food chain.

“Missing eyes, deformed hind legs, missing limbs, extra limbs, partial limbs, limbs that are bent or bony, and abnormally thin or weak limbs are some of the reported frog abnormalities in the Western ghats,” said Dr. S. Muralidharan from the Division of Ecotoxicology at Salim Ali Centre for Ornithology & Natural History.

Since frogs are very sensitive to changes in their habitats, studying them would yield clues to the state of the environment, says Dr. Karthikeyan Vasudevan of the Centre for Cellular and Molecular Biology (CCMB), Hyderabad. “A few decades ago, the population of the bald eagle came down in the United States due to use of the DDT pesticide. We cannot commit a similar mistake. More studies are needed to fully understand the issue,” he said.

Independent studies on the excessive use of pesticides and on the impact of pesticides on amphibians in laboratory conditions suggest a strong link between pesticide use and frog deformities.

Breeding season hit

Dr. H.P. Gurushankara from the Central University of Kerala and Dr. S.V. Krishnamurthy from Kuvempu University, Karnataka, conducted a survey in the early 2000s and found an increased number of deformities in the frogs inhabiting paddy fields. Not only do many amphibians breed in the shallow waters of paddy fields, pesticide applications also coincide with the breeding periods of frogs.

Frog with missing eye.

 

“Considering the scenario of global amphibian population decline, we analysed the impact of pesticides on the amphibians in laboratory conditions and concluded that pesticides could act as a major factor behind the depletion of larval and adult population,” Dr. Gurushankara said.

The cardamom plantations of Kattapana, which reportedly use a large number of illegal pesticides, are also suspect. “These pesticides are banned in Kerala. But they are illegally brought in from Tamil Nadu,” said Dr. Muthuswamy Murugan from Kerala Agricultural University.

“Pesticides mainly affect the reproductive health of frogs. But the deformities are only 10% of the actual problem. These chemicals ultimately reach the soil and move into the water system where the larval stage (tadpoles) of the frog develops. We are studying the causes of these deformities though ‘in vitro’ conditions, and trying to assess the environmental health of the region,” said Dr. S.D. Biju from Delhi University.