A Blind Fish Rode Up a Farm Borewell and Turned Out to Be New

Pump a handpump in the flat farmland of Bihar long enough and, once in a great while, something small and pale slides out with the water. In a village called Balgangwa, near where India meets Nepal, one of those things turned out to be a fish nobody had ever named. It is about four centimetres long, the colour of nothing much, with eyes reduced to specks under skin and no trace of the pigment that gives most animals their markings. Researchers have described it as a new genus and species, Gangaichthys indonepalicus, and it is the first fish known to live in the vast groundwater beneath the Indo-Gangetic Plain.

That plain is one of the most heavily farmed, densely peopled stretches of land on Earth, watered by the Ganga and drilled through with countless borewells. Nobody had thought to look for fish in the aquifer under it.

A Video From the India-Nepal Border

The trail started, of all places, on TikTok. In 2024 a clip surfaced from the India-Nepal border area showing a tiny, near-colourless fish with shrunken eyes wriggling in water freshly pumped from a borewell. To an ichthyologist that combination reads like a flag: reduced eyes and lost pigment are the classic marks of an animal that has spent its evolutionary life in the dark. “The unique morphology of the fish in the video, and the fact that there are no known stygobitic fish known from the region, motivated us to track down the species to ascertain its identity,” the research team said. Stygobitic is the word for a creature that lives out its whole existence in groundwater.

Finding it again was the hard part. A borewell is a machine-drilled shaft reaching down to the water table, and you cannot exactly go fishing in one. The team, led by researchers at the Thackeray Wildlife Foundation in Mumbai, took to it by hand.

They worked more than 15 handpumps over roughly a week, pumping thousands of litres up from as deep as ten metres and watching what came out. “Procuring samples of this unusual fish was challenging,” says Akshay Khandekar of the foundation. Getting owners to let the team drain their wells was its own negotiation, he notes, and the manual pumping only got harder from there.

In the end they had three fish from two borewells: one whole, live animal that became the holotype, the reference specimen against which the species is defined, plus two that came up damaged and did not survive. (The exact order in which the intact and damaged fish emerged is told slightly differently by the team’s paper and their press release, a small snag worth noting given only three specimens exist at all.) One more was collected from a second handpump about a kilometre away.

What the Micro-CT Scan Showed

With a single intact specimen, the team had to be careful. They photographed it live, then turned to a micro-CT scanner at the National Centre for Biological Sciences in Bengaluru, which builds a three-dimensional model of the skeleton without cutting anything open. The scan, plus fragments of one mitochondrial and one nuclear gene, told two stories at once. Genetically the fish sits firmly inside the earthworm eels, the family Chaudhuriidae: it differs by just over 20 per cent in one common gene from the two relatives that have comparable data, more than enough to mark it as distinct. Skeletally it carries a suite of quirks, narrow tapering spines along the backbone, a single fused tail-fin support, an elongated bone in the cheek, that set it apart from every other genus in the family. It has 64 vertebrae and a lone pectoral fin-ray where its cousins have several.

Some of what makes it strange is exactly what you would expect of a life underground. Reduced eyes and missing pigment turn up again and again in cave animals that are not related to each other, the product of relaxed selection in a place where sight and colour buy you nothing, rather than any shared ancestry.

There is a caveat the scan itself imposes. The fish appears to have no ribs, unusual even among its miniature relatives, but the researchers scanned without a contrast agent, which means very thin or cartilage-like bone would not show up. With only the one intact fish, they could not scan again. So the missing ribs are reported as apparent, not settled. The genus’s exact perch within the family is provisional too: only two of the seven earthworm-eel genera known before this have any comparable gene data. Confirming Gangaichthys as its own genus is a job for future work with more sequences.

Naming it, at least, was the team’s to enjoy. “Gangaichthys means fish of the Ganga,” says Ishan Agarwal of the foundation, tying the animal to the river that feeds and, for many, sanctifies the plain it hides beneath. The species name, indonepalicus, marks a range that straddles the border: the known localities, two in Bihar and one photographed across the line in Nepal, all fall within an 11-kilometre stretch. The find pushes the family’s range some 500 kilometres west of where it had been recorded, and makes this the fifth earthworm-eel genus known from just a single species.

What lingers is how ordinary the fish’s hiding place is. India’s richest seam of groundwater fish sits far to the south, in the lateritic aquifers of Kerala, which hold eleven known species; the Gangetic aquifer, tapped by millions for drinking and irrigation, had yielded none until now. A pale eel coming up a farmer’s pump is a reminder of how much may be living unseen beneath fields nobody thinks of as wild, and of how rarely we get a look: only a small fraction of the world’s subterranean fishes come from aquifers, and almost always by chance when someone empties a well, and of how little stands between that hidden fauna and the pumps, as groundwater is drawn down and fouled across the region. Whatever else is down there has been sampling the surface, one bucket at a time, without our noticing.

FAQ