TikTok video leads to discovery of rare underground eel in India

Researchers have unearthed a new genus and species of underground eel dwelling beneath the Indo-Gangetic Plain in Bihar, northern India. Dubbed Gangaichthys indonepalicus, this diminutive, colorless creature is the first subterranean fish documented from the Gangetic Basin. The research, published in ZooKeys, was conducted by an international team of scientists hailing from Mumbai, India; Kolhapur; Shanghai; and Gopalpur-on-Sea, India.

The discovery began following a TikTok video in 2024 showing an unusual, tiny fish emerging from a borewell near the India-Nepal border. The distinctive morphology of the fish, coupled with the absence of stygobitic fish known from the region, prompted the research team to identify the species and determine its identity. Gathering physical samples required extensive fieldwork in Bihar, where scientists manually extracted thousands of liters of water from local hand pumps to search for the elusive fish.

Despite the challenges, the team successfully obtained a specimen after manually pumping water from a borewell and encountered the first intact specimen after an additional 500 liters of water (132 gallons) had been pumped.

Measuring approximately 4 centimeters (1.6 inches) in length, Gangaichthys indonepalicus possesses physical adaptations suited to life in complete darkness, such as reduced eyes covered by skin, an unpigmented translucent body, and a lack of apparent ribs. Advanced micro-CT scanning and genetic analysis confirmed its status as a completely distinct genus within the earthworm eel family Chaudhuriidae.

The new genus name, Gangaichthys, translates to "fish of the Ganga" in reference to the mighty river that flows through India. The species name, indonepalicus, reflects the fish's distribution across the border between India and Nepal.

The discovery holds significant implications for understanding India's biodiversity, as the country encompasses a wide range of climates and topographies, with many species yet to be identified. This groundbreaking finding underscores the challenges and importance of exploring subterranean habitats in India, as well as the broader context of biodiversity research in the nation.