Evolution in action?

The newfound fish is undoubtedly closely related to a surface-dwelling fish known as the golden mahseer (Tor putitora), Harries says.

The only observable differences between the two animals, he explains, are that the cave fish lack pigmentation—appearing a white, almost translucent colour—and their eyes are poorly developed or even non-existent.

The cave creatures are also smaller than golden mahseers, an endangered fish that can grow to many feet in length.

Though they look very alike in body shape and structure, the scientists think that the cave fish may be different enough from surface-dwelling golden mahseer to qualify as a unique species.

A seemingly analogous situation is occurring right now with the Mexican tetra (Astyanax mexicanus), a cave fish that’s very similar to tetras that live at the surface, albeit lacking eyes and pigment. The theory goes that some surface fish were isolated underground long ago, and then began to develop traits to better suit their new, lightless home.

There are multiple studies aimed at understanding the genetic process by which the Mexican tetra loses its colour and eyesight, and similar research on this Indian species could provide “opportunities to explore the genetic basis of these adaptations,” Ornelas says. A thorough understanding of pigmentation and vision could have wide and perhaps unexpected applications.

The Mexican tetra, and perhaps the newfound Indian fish, could be an example of “speciation and evolution in progress,” Harries says.