Gitchak nakana: New Subterranean Fish Found in Assam

In a major scientific breakthrough, researchers have identified a new genus and species of subterranean fish, “Gitchak nakana”, from a dug-out well in western Assam. The discovery marks the first aquifer-dwelling, or phreatobitic, fish recorded from Northeast India. The findings were published in the journal “Scientific Reports”, a Nature Portfolio publication, underscoring the global importance of the discovery.

Discovery in Assam’s Groundwater Aquifer

The research was led by Ralf Britz of the Senckenberg Naturhistorische Sammlungen Dresden, in collaboration with Wimarithy K. Marak of Assam Don Bosco University and other national and international scientists.

The fish was collected on three separate occasions from the same well in a village at the foothills of the Shillong Plateau near the Brahmaputra Valley. Its habitat within a groundwater aquifer makes it exceptionally rare, as fewer than 10 per cent of the world’s known subterranean fishes inhabit such environments.

Unique Troglomorphic Adaptations

“Gitchak nakana” is a miniature cobitid loach that is blind and pigmentless. It displays pronounced troglomorphic traits, including complete loss of eyes and body pigmentation—typical adaptations to life in total darkness.

One of its most striking anatomical features is the complete absence of a skull roof. The brain is covered dorsally only by skin, a characteristic not observed in other known cobitid genera. These distinct morphological traits warranted its classification as a new genus and species.

Scientific Significance and Evolutionary Insights

Globally, more than 300 fish species are known from subterranean habitats, but most are cave-dwelling. The Shillong Plateau already hosts cave fishes such as species of “Schistura” and the large subterranean fish “Neolissochilus pnar”. However, “Gitchak nakana” is the first aquifer-dwelling fish reported from the region and the first subterranean cobitid recorded from Northeast India.

Researchers have also proposed hypotheses regarding its evolutionary position within cobitid loaches, particularly in light of its unusual skeletal structure.

Important Facts for Exams

• Phreatobitic species inhabit groundwater aquifers rather than caves.
• Troglomorphic traits include loss of eyes and pigmentation.
• The Shillong Plateau is a recognised hotspot for subterranean biodiversity.
• Scientific Reports is a peer-reviewed journal under the Nature Portfolio.

Implications for Groundwater Biodiversity

The discovery expands understanding of subterranean biodiversity in Northeast India and highlights the ecological importance of groundwater ecosystems. It suggests the presence of previously undocumented underground fauna in the region. Scientists stress the need for systematic exploration and conservation of fragile subterranean habitats, particularly as groundwater systems face increasing environmental pressures.