Viral video leads scientists to first known subterranean fish from the Gangetic Basin

Scientists have confirmed a tiny, translucent fish from groundwater beneath northern India as a new genus and species. Named Gangaichthys indonepalicus, the roughly four-centimetre animal is the first subterranean fish recorded from the Gangetic Basin. Micro-CT imaging and genetic analysis established that it represents a distinct genus within the earthworm eel family Chaudhuriidae.

The investigation began with a 2024 TikTok clip showing an unusual fish emerging from a borewell near the India-Nepal border. Researchers traced the sighting to Bihar, then sought permission to draw water from local handpumps and wells. They manually pumped about 2,000 litres before recovering a specimen that was damaged and died, followed by another 500 litres before finding the only intact specimen, later designated as the species’ holotype.

The fish bears striking adaptations to permanent darkness: reduced eyes covered by skin, an unpigmented body and an apparent absence of ribs. Its genus name means “fish of the Ganga,” while its species name reflects its location near India and Nepal. Researchers say the discovery also points to large gaps in knowledge about India’s biodiversity, especially within difficult-to-sample underground habitats.