A tiny fish wriggling out of a borewell near the India-Nepal border is likely something you’d scroll past on social media. But a TikTok video of this peculiar creature sent researchers on an extraordinary search beneath one of South Asia’s largest river plains.
According to the study published in ZooKeys, after manually pumping hundreds of gallons of groundwater, the research team recovered an animal unlike any fish previously documented in the region. Named Gangaichthys indonepalicus, the translucent earthworm eel represents both a new species and genus — and the first known subterranean fish from the Gangetic Basin.
“The unique morphology of the fish in the video, and the fact that there are no known stygobitic fish known from the region, motivated us to track down the species to ascertain its identity,” said the research team in a press release.
TikTok Discovery Leads to a Difficult Search
The investigation began in 2024, when researchers encountered a short TikTok clip showing a slender, colorless fish emerging from a borewell. Its unusual appearance immediately stood out.
Finding the fish again was far more difficult than watching the original video. Researchers had to identify possible borewells, get permission from their owners, and repeatedly operate local handpumps.
“Procuring samples of this unusual fish was challenging. Identifying potential handpumps (borewells) and wells, and obtaining permissions 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,” said researcher Akshay Khandekar, in the release.
The first specimen appeared only after the team pumped approximately 528 gallons (2,000 liters) of water. It was injured during its journey to the surface and died immediately. Researchers then pumped another 130 gallons (500 liters), recovering a second intact individual that became the species’ holotype.
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A Translucent Earthworm Eel Adapted to Total Darkness
Measuring only about 1.5 inches (4 cm) long, G. indonepalicus has several traits associated with a lifetime underground. Its nearly transparent body lacks pigment, while its reduced eyes are concealed beneath skin. The fish also appears to have no ribs.
Micro-CT imaging allowed researchers to examine its delicate internal anatomy without damaging the only intact specimen. Combined with genetic testing, the scans revealed that the fish belongs to Chaudhuriidae, a family commonly called earthworm eels. Its anatomy was distinctive enough, however, to place it in an entirely new genus.
The discovery underscores how little scientists know about subterranean ecosystems. Animals living inside aquifers and groundwater channels rarely encounter conventional sampling equipment, meaning entire lineages could remain hidden beneath densely populated landscapes.
How G. indonepalicus Got Its Name
The new name of the genus honors the river system concealing the fish.
“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,” explained researcher Ishan Agarwal.
Its species name also recognizes the location where it surfaced: “As the species occurs on the border between India and Nepal we picked indonepalicus as the specific epithet, which reflects the distribution of the species,” said researcher Tejas Thackeray.
Overall, its name and discovery suggest that even beneath one of the world’s most familiar river basins, an unseen world is still waiting to be found.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in ZooKeys: Gangaichthys indonepalicus, a new genus and species of miniature stygobitic earthworm eel (Synbranchiformes, Chaudhuriidae) from alluvial aquifers in the Indo-Gangetic Plain, Bihar, northern India