Two New Blind Subterranean Fish Species Found in Assam Wells

Researchers have discovered two new species of blind, subterranean fish living in groundwater wells in Assam's Goalpara district. A researcher named Wimarithy K. Marak first encountered one of the creatures years ago while drawing water from a well and initially mistook it for a worm.

The Species

The first species, named Gitchak nakana, is a two-centimetre long blind loach with a transparent body and a striking blood-red appearance due to visible blood and internal organs. The second species, named Rakthamichthys anchi, is a slender eel-like fish measuring around 310 millimetres that belongs to the swamp eel family Synbranchidae. Both species inhabit underground aquifers and travel through water-filled spaces, though researchers have kept the exact discovery location secret to prevent exploitation of the populations.

Scientific Collaboration

Scientists published two studies describing the new fish earlier this year after collaborating with German researchers to perform micro CT scans on preserved specimens. German ichthyologist Ralf Britz noted that finding subterranean fishes in alluvial deposits is highly unexpected because it is a quickly changing environment. Meanwhile, Professor Rajeev Raghavan from KUFOS explained that people often confuse these unusual creatures with earthworms or snakes, which can lead to human-fish conflicts and the killing of the animals out of fear that they are toxic.

Habitat and Threats

Experts note that wells act as semi-open systems where these animals find food, light, and oxygen, though their low metabolic rate allows them to go for months without food after feeding. Geologist Prerona Das stated that the Brahmaputra floodplain features multi-layered aquifers extending to 400 metres depth with high lateral connectivity. Australian ecologist Grant Hose added that stygofauna like these fish help groundwater ecosystems by grazing on bacteria and preventing clogging. However, researchers warn that unmanaged pollution from urbanisation, agriculture, and industrial activities threatens these poorly understood underground habitats.

Context

Groundwater ecosystems and aquifers are extreme underground environments characterised by total darkness, limited oxygen, and scarce food resources. Organisms that live in these hidden spaces have evolved special traits like transparent bodies and very slow metabolic rates to survive without sunlight. Studying these rare creatures helps scientists understand the health of deep water systems that remain largely unmapped across northeast India.