It is pollution that made Gangetic dolphins ‘blind’, says Uma Bharti

Species not using its eyes after 125 years of pollution: Minister

Uma Bharti

Nothing, not even Darwinian evolution, can challenge Union Water Resources Minister Uma Bharti’s stance that pollution has blinded the Gangetic river dolphin.

On Aug 4, in the Lok Sabha, Ms. Bharti stated that “pollution for over 125 years in the Ganga” had caused the dolphin to “stop” using its eyes and rely on other senses to navigate. Platanista gangetica , the biological name of the Gangetic river dolphin, also called the “blind” river dolphin or the “side-swimming dolphin” is unique to India and an endangered species.
A Right to Information query by a media agency to the Water Resources Ministry earlier this month found that the Ministry had conducted no study to establish a theory on why the mammal was blind. On Wednesday, the Ministry put out a press statement explaining that Ms. Uma Bharti was right and “…a presentation was made by an expert (to the Minister) on aqua life in which the Minister was informed that dolphins in Ganga are getting blind due to pollution in the river. Therefore, the statement by the Minister is factually correct,” the statement said.

A Ministry spokesperson did not share the name of the expert and The Hindu could not obtain this information from other departmental officials.

Evolutionary biology has it that the Gangetic dolphin has been ‘blind’ for about 20 million years and shares its limited eyesight with its international freshwater river-dolphin cousins, namely the Yangtze, Amazon, La Plata and the Indus dolphins.

“The Gangetic dolphin lost its eyes in the course of evolution to adapt to the muddy water of rivers. They largely navigate by echo-location or sonar,” said Qamar Qureshi, a wildlife ecologist who specialises in river-dolphin conservation at the Wildlife Institute of India.

The mammal evolved over millennia, according to an October 2000 paper in the Proceedings of the Royal Society of London, Evolution of river dolphins , when rising sea levels inundated large areas of the Indo-Gangetic basin, creating a shallow marine habitat.

Species such as the Gangetic dolphin were able to adapt to this muddied, saline environment that however came at the expense of vision, or at least vision in the way it works in humans. Gangetic rivers dolphins navigate using sound waves made by clicking sounds through their throat that bounce off targets and return to their large, flat heads with extremely sensitive auditory systems. They also have rods and cones, found in mammal eyes, that help tell light from dark.

“Pollution is certainly responsible for the plight of the dolphin but not in this way,” said Mr. Qureshi. Dams over the Ganga and Brahmaputra, overfishing and industrial effluents had made survival of the mammal difficult in India. There are no more than 2,500 dolphins in India with most along the Brahmaputra, Bihar, Allahabad and Chambal regions, he added.

One of the stated aims of the Rs. 20,000 crore National Mission for Clean Ganga (NMCG) is to improve aquatic life in the river and restore dophin populations. On Wednesday, however, the NMCG had ordered an inquiry to find out how “factual information” (from the unnamed expert who had briefed the Minister) was not added to the RTI query, the Ministry statement added.
Source - The hindu

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