Two New Subterranean Fish Species Discovered in Wells in Assam’s Goalpara
Scientists have discovered two previously unknown fish species living in underground water systems in Assam’s Goalpara district, highlighting the region’s rich and largely unexplored biodiversity.
The newly identified species, Gitchak nakana and Rakthamichthys anchi, are adapted to subterranean environments where sunlight is limited or entirely absent. Their discovery offers fresh insights into how aquatic life survives in the dark and often resource-scarce conditions beneath the Earth’s surface.
Gitchak nakana is a tiny, transparent and blind loach measuring around two centimetres in length. Its translucent body allows its blood and internal organs to be seen, giving it a reddish appearance. The species has no functional eyes, an adaptation suited to life in darkness. Its name comes from the Garo language, with “Gitchak” referring to its distinctive red colour.
The second species, Rakthamichthys anchi, is a slender, transparent, eel-like fish belonging to the swamp eel family, Synbranchidae. Its elongated body and specialised features distinguish it from many fish found in surface waters.
The discoveries were made following observations by Wimarithy K. Marak. The first specimen of Gitchak nakana was collected in March 2021 after Marak spotted an unusual organism in a well and shared its photograph with her supervisor. In May 2024, a relative encountered another unusual fish while cleaning a well. The specimen was later identified as Rakthamichthys anchi.
Subterranean fish inhabit underground aquatic environments, including groundwater-filled spaces and aquifers. With little or no sunlight and limited access to food and oxygen, these species often develop distinctive characteristics, such as reduced eyes and transparent bodies, to survive in their unusual habitats.
Researchers say such discoveries are important for understanding evolution, biological adaptation and the diversity of groundwater ecosystems, which remain largely unexplored.
However, these fragile habitats face growing threats from groundwater pollution, excessive extraction and human activities. Sewage, agricultural chemicals and other waste can contaminate underground water systems, while unsustainable groundwater use can disturb the conditions essential for the survival of specialised species.
The discovery of Gitchak nakana and Rakthamichthys anchi underscores the remarkable life hidden beneath Assam’s surface and highlights the need to protect groundwater ecosystems, which may harbour many more species yet to be identified.
