14 August,2026 08:51 AM IST | Mumbai | Ranjeet Jadhav
Gangaichthys indonepalicus, the newly discovered species. PIC COURTESY/Thackeray Wildlife Foundation
A short video posted on social media in 2024 has helped scientists uncover a creature never before recorded from the Gangetic Basin - a tiny, colourless underground fish living beneath the Indo-Gangetic Plain in Bihar. Researchers from Mumbai-based Thackeray Wildlife Foundation (TWF) have described the fish as a new genus and species, Gangaichthys indonepalicus, an earthworm eel that appears to have evolved several adaptations to survive in complete darkness. It is the first subterranean, or stygobitic (living underground, beneath the surface of the soil or rock), fish recorded from the Gangetic Basin.
The discovery was made by Akshay Khandekar, Ishan Agarwal, and Tejas Thackeray from the Thackeray Wildlife Foundation, along with You He from the Shanghai Synchrotron Radiation Facility at the Chinese Academy of Sciences, and Anil Mohapatra from the Zoological Survey of India. The investigation began after the researchers came across a video showing an unusual tiny fish emerging from a borewell near the India-Nepal border.
Researchers travelled to Bihar and manually pumped thousands of litres of water from hand-pumps and borewells in their search. "Identifying potential hand-pumps and wells, and obtaining permission from their owners to extract water for the purpose of searching for the fish proved difficult. This became more intensive when we finally began manually pumping water," Khandekar explained.
The first specimen emerged after pumping approximately 2000 litres of water, but sustained damage during the process and died immediately. The second and only intact specimen (later designated as the holotype of this species) was found from the same borewell after pumping an additional 500 litres of water.
Measuring around four centimetres, Gangaichthys indonepalicus has reduced eyes covered by skin, a translucent body without pigmentation, and an apparent absence of ribs - features associated with life underground in perpetual darkness. Micro-CT scans and genetic analysis confirmed that the fish belongs to a completely distinct genus within the earthworm eel family Chaudhuriidae.
According to Agarwal, Gangaichthys means fish of the Ganga. "The Ganga or Ganges is one of the most important rivers in India, both as a source of fresh water, food, and livelihood for millions of people; besides having an important role in the Hindu religion. This is the first stygobitic fish from the Indo-Gangetic plains and from the Gangetic basin."
According to Tejas Thackeray, as the species occurs on the border between India and Nepal, indonepalicus was picked as the specific epithet, "which reflects the distribution of the species."
The discovery highlights how little is known about India's subterranean biodiversity. "India is a diverse country, spanning huge gradients in climate and topography and biogeographic regions. However, there is a huge gap in knowledge, both Linnaean and Wallacean shortfalls, with many more species yet to be discovered," Agarwal said.
Akshay Khandekar, researcher, TWF
âThe unique morphology of the fish in the video, and the fact that there are no known stygobitic fish from the region, motivated us to track down the species to ascertain its identity. However, procuring samples of this unusual fish was extremely challenging'
