A marvel of evolution at the bottom of a well: scientists report discovery of blind subterranean fish in Assam

Going ahead, the researchers will be looking to establish the geographical area where the 2-cm-long fish named Gitchak nakana is present.

The fish, named Gitchak nakana, is a member of the Cobitidae family. (Photo by special arrangement)

3 min readBengaluruMar 10, 2026 02:32 PM IST First published on: Mar 10, 2026 at 02:32 PM IST

An international team of scientists has discovered a rare species of blind subterranean fish from a hand-dug well in Assam. The 2-cm-long fish was dubbed Gitchak nakana, from Garo language words describing its lack of sight and reddish colour (due to its mostly transparent skin).

The team, consisting of scientists Ralf Britz, Wimarithy K. Marak, Kangjam Velentina, Yumnam Lokeshwor, Rajeev Raghavan, Amanda K. Pinion & Lukas Rüber, reported the discovery in an open-access paper in the Scientific Reports journal.

The fish is a member of the Cobitidae, or “true loach”, family.

Speaking to indianexpress.com, Rajeev Raghavan of the Kerala University of Fisheries and Ocean Studies (KUFOS) said, “In 2021, there were a few specimens collected and again after a few months…. There are loaches in the Northeast which occur in caves. This is the first time we have had a fish from groundwater. In a cave, there can be water coming in from the outside during rains, etc.”

He explained, “The fish comes from a closed underground system, dwelling in an aquifer. This is the first such fish discovered in the Northeast. Anatomically, there are many differences. It completely lacks the roof of the skull, a characteristic found in a very few species outside India.”

The research paper notes, “Like many subterranean fishes, it also lacks externally visible eyes. Its barbels, including its nasal barbels, are well-developed, comparatively long and densely covered in taste buds…”
KUFOS has been involved in the discovery and study of fish species from cave and subterranean environments in India. Among these is the largest known such fish Neolissochilus pnar, the cave mahseer.

Explaining the circumstances of the discovery, Raghavan said, “Normally, these subterranean fish live in aquifers and groundwater and get into the wells. These are extreme habitats with no light, little oxygen, food, or space. So they might get into the wells looking for food, or get swept in from underground during seismic activity. Most of these species are discovered when they get into wells, since there are not really any methods to look at groundwater systems directly.”

He added that a possible food source for these fish might be micro-sized crustaceans or tiny insects.
At the moment, there do not appear to be any direct threats to the habitat of these fish. However, as a precaution, the team has not disclosed the precise location of the discovery to avoid harvesting for the aquarium trade before the fish’s geographical distribution has been studied.

Going ahead, the researchers will be looking to establish the geographical area where the species is present. This will be done via the study of “environmental DNA”, i.e by taking samples of water or other substances and testing them for the presence of a particular species. Other aspects of study could include an examination of the reasons why the fish evolved unique features like the absence of the skull roof.