A TikTok video led to the discovery of a new fish species. It lives underground and resembles an eel

It all started with a short TikTok video. A small, unusual fish shown in a recording from the border region of India and Nepal caught the attention of scientists and led to the discovery of a previously unknown species, Gangaichthys indonepalicus.

From a TikTok video to a search underground

The story began in 2024. A video appeared on TikTok showing a small, elongated fish extracted from a borehole reaching groundwater near the India-Nepal border. The authors of the subsequent study drew attention to its unusual appearance: a pale body resembling an eel in shape and very small eyes. No fish adapted to permanent life underground had previously been discovered in this region.

Scientists began their search in Bihar, in northern India. It was not easy. During fieldwork in 2024 and 2025, they examined more than 15 wells and boreholes, manually pumping out thousands of liters of water.

The first specimen appeared only after approximately 2,000 liters had been pumped out. However, it was damaged and did not survive. After another 500 liters were pumped from the same borehole, an intact fish was recovered. It later became the holotype, the specimen serving as the basis for the formal description of a new species. The researchers managed to obtain only three individuals.

Gangaichthys indonepalicus – a fish adapted to darkness

The intact specimen measured 40.6 mm in length. The fish has an elongated, almost transparent body with virtually no pigmentation. Its eyes are strongly reduced and covered by skin. Such features are often found in organisms that spend their entire life cycle in groundwater. In an environment without light, vision and coloration have no significance.

Analysis of the holotype’s anatomy, micro-CT imaging, and genetic studies showed that the scientists were dealing not only with a new species, but also with a new genus belonging to the family Chaudhuriidae.

It resembles an eel, but it is not one

The elongated body makes Gangaichthys indonepalicus look like an eel at first glance. However, it does not belong to the true eels of the order Anguilliformes, but to a separate order, Synbranchiformes. The resemblance therefore concerns primarily body shape rather than close evolutionary relatedness.

The common English name for members of the family Chaudhuriidae can also be somewhat misleading: earthworm eels. The term refers to their appearance and does not mean that they are eels in the taxonomic sense.

So where did its scientific name come from? The authors referred to the place where it was discovered. Gangaichthys means fish of the Ganges and refers to the Ganges basin, while the epithet indonepalicus points to the India-Nepal border, where its presence was recorded.

Unknown life beneath the Indo-Gangetic Plain

All specimens of Gangaichthys indonepalicus obtained so far came from the area around the village of Balgangwa, located in Pashchim Champaran district, Bihar. Researchers also have photographic documentation from the area around Triveni on the Nepalese side of the border. All known sites are close to one another, no more than 11 km apart.

The fish appeared exclusively in water pumped from boreholes reaching approximately 10 m below the surface. Searches conducted in nearby open wells and water bodies did not produce any further discoveries. According to the researchers, this indicates that G. indonepalicus is a stygobiont species, meaning one whose entire life cycle is associated with groundwater.

This is what makes the discovery particularly interesting. G. indonepalicus is the first subterranean fish known to science from the Ganges basin and the Indo-Gangetic Plain, while also demonstrating how little we know about organisms inhabiting underground aquifers. Accessing such habitats is difficult, and direct observation of the fauna living there is often impossible. For now, it is not known how large the population of the new species is or how far its actual range extends. The study’s authors also did not provide a formal assessment of the species’ conservation status.

The story of G. indonepalicus shows that new species are not always discovered during planned scientific expeditions. In this case, everything began with a video posted on social media, which ultimately led to the description of a fish previously unknown to science.

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main photo: Ishan Agarwal, license: CC BY