Snakeheads are native to Africa and Asia and are distinguished by their long dorsal fins, large mouths, and ability to breathe air using what is known as a suprabranchial organ in their gill cavity. These fishes usually live in freshwater rivers or wetlands making this new discovery, living in an environment unlike any documented before, particularly exciting.

The species was discovered by chance after the devastating floods that hit Kerala in August last year. Pictures of the fish were posted online after the animals had seemingly been washed out of the aquifers – underground, permeable rocks that carry water. The images prompted the Kerala University of Fisheries and Ocean Studies to investigate.

Dr Ralf Britz, a researcher at the Natural History Museum who co-authored the paper which describes the species said: 'As soon as I saw higher quality images it became pretty clear that it was a snakehead. But having a snakehead from a subterranean habitat is an exciting find. This fish is very unusual.'

Globally subterranean fishes are mainly represented by only two groups, the catfishes and carps, as species in these groups are thought to be pre-adapted to life underground. Snakeheads, however, don't tend to have any adaptations that might also be suited to an underground lifestyle.

Ralf explains: 'The surprising part is that - assuming it is subterranean - it doesn't have the typical adaptations you would expect from a subterranean fish. This could mean one of two things. Either the fish only acquired this subterranean mode of life recently, or it is living in some kind of transition zone where it is still moving between the underground and above ground habitats. We simply don’t know and so that is something we'd be very interested in finding out.'

The new fish is highly distinctive when compared the known snakeheads. In comparison, A. gollum has an incredibly long and eel-like body; numerous scales along its body, a very long anal fin running along its belly and tail and has lost the ability to maintain buoyancy in the water column. It is possible that some of these aspects could be adaptations to their underground existence.

This is now the eighth species of subterranean fish that has come out of the aquifers beneath Kerala, leading researchers to believe that there must be a hidden ecosystem existing over 40 metres below the surface.

The paper is published in the journal Zootaxa.

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