Researchers Find Two Subterranean Fish in Assam

Two previously unknown subterranean fish species were discovered in wells in Assam’s Goalpara district. The species, “Gitchak nakana” and “Rakthamichthys anchi”, were announced by Assam’s Environment and Forests Minister Jayanta Malla Baruah on 21 October 2026.

Species and their features

“Gitchak nakana” is a blind loach measuring about two centimetres. Its transparent body exposes blood and internal organs, giving it a reddish appearance. Researcher Wimarithy K. Marak collected its first specimen in March 2021 after noticing an unusual creature in a well and sharing a photograph with her supervisor. “Rakthamichthys anchi” is a slender, transparent, eel-like fish in the swamp eel family Synbranchidae. Its approximately 310-millimetre holotype—the name-bearing specimen used to describe a species—was collected in May 2024 while a well was being drained.

Scientific identification

Researchers examined the specimens in collaboration with international scientists and used micro-computed tomography (micro-CT) scanning. The technique uses X-rays to produce detailed images of internal structures without requiring conventional dissection. The two species were found in wells, which can provide access to groundwater habitats beneath the surface. Subterranean environments include groundwater-filled cavities and other underground spaces, where organisms may experience limited light and restricted habitat connectivity.

Groundwater habitats and protection

Researchers have withheld the exact discovery locations to reduce the risk of exploitation. They have also called for protection of the underground habitats from pollution. Contamination can enter groundwater through sources such as waste disposal and polluted surface water. The discoveries add to records of fish diversity in Assam’s lesser-explored groundwater ecosystems. The specimens were collected from wells in Goalpara district, but the precise sites have not been made public.

Important Facts for Exams

• Goalpara district lies in western Assam, in the Brahmaputra Valley region.
• Synbranchidae is the family commonly known as swamp eels, within the order Synbranchiformes.
• A holotype is the single specimen designated as the name-bearing type when a species is formally described.
• Micro-computed tomography uses X-rays to create detailed images of an object’s internal structure.

“Gitchak nakana” is a blind, transparent loach, while “Rakthamichthys anchi” is an eel-like swamp eel. The exact locations of their discoveries in Goalpara district have been withheld.