# A miniature, subterranean, blind cobitid loach, Gitchak nakana, new genus and species, is the first groundwater-dwelling fish from Northeast India

## TL;DR

A new blind, miniature fish species, Gitchak nakana, was discovered in an aquifer in Northeast India, marking the first subterranean fish found in this region.

## Contribution

The discovery of a new genus and species of subterranean fish with unique anatomical features in Northeast India.

## Key findings

- Gitchak nakana exhibits troglomorphies, including blindness and lack of a skull roof.
- It is the first aquifer-dwelling fish reported from Northeast India.
- The species represents a new genus within the Cobitidae family.

## Abstract

Subterranean animals are commonly met with considerable fascination, by both laymen and biologists. While most of these animals have been reported from caves, some species have adapted to other underground habitats. One special subterranean aquatic habitat are aquifers, which are home to a number of invertebrates and fishes. Of the more than 300 known subterranean fishes, fewer than 10% have been recovered from aquifers and are encountered only rarely and serendipitously. Here we report the discovery of a tiny, blind loach of the family Cobitidae from a dug-out well in Assam, India, which exhibits a number of characters commonly associated with subterranean life, so-called troglomorphies. This loach, described here as Gitchak nakana, represents a new genus and species, differing from all other genera of cobitids by a number of unique characters. The most unusual among these is the complete lack of a skull roof with the brain covered dorsally only by skin. Gitchak nakana is the first aquifer-dwelling (phreatobitic) fish from Northeast India, and marks the first discovery of a previously unknown subterranean fauna in this part of Asia.

The online version contains supplementary material available at 10.1038/s41598-026-40425-6.