A video posted on TikTok led a team of researchers to discover a new fish species and genus living in groundwater beneath the Ganges Plain in northern India. The researchers named the fish Gangaichthys indonibalikus after studying its anatomical and genetic characteristics.
Tracking the video and finding specimens
The search began in 2024, when scientists saw a video filmed near the Indian-Nepalese border showing a small, pale aquatic creature emerging from a well used to access groundwater. The fish’s nearly transparent body and small, skin-covered eyes caught the researchers’ attention, as did its emergence from an underground environment. The team traced the filming location and searched for live specimens in groundwater wells in Bihar.
The fish’s adaptations to groundwater
All three specimens were collected from groundwater wells, supporting the fish’s association with this environment rather than its being an accidental presence in water emerging from the well. Examination showed that the fish’s body was almost devoid of pigment, giving it a pale or nearly transparent appearance, while its reduced eyes were covered by skin tissue.
It also appears to lack ribs, an unusual trait among fish that researchers associate with its underground lifestyle. Organisms that spend their entire life cycle in groundwater environments face conditions unlike those in surface waters, including the absence of light and limited space for movement.
Scientific classification and genetic divergence
Under these conditions, some traits, such as vision and pigment production, become less important to organisms adapted to perpetual darkness. Despite its elongated body, which may make it resemble a snake or eel, the fish belongs to the family Chaudhuriidae, which includes small eel-like fish, but it is not classified as a true eel.
Anatomical and genetic studies showed that the creature differs sufficiently to be classified in a genus separate from the known species and genera in the family. Molecular analyses found more than 20% genetic divergence from two genera in the family for which mitochondrial DNA comparison data were available.
The team used micro-computed tomography and genetic analysis to identify the creature’s anatomical and genetic traits. Researchers from India and China published its scientific description in the journal ZooKeys, identifying it as a new species belonging to a new genus as well. Gangaichthys indonibalikus is the first documented subterranean fish in the alluvial aquifers of the Ganges Basin and the first known subterranean member of the family Chaudhuriidae.
Its scientific name refers to the Ganges River and the location where it was found near the border between India and Nepal.
