World?s largest cave fish discovered in India

And perplexed.“My first reaction upon seeing the fish myself was, I’m going to need a bigger net.”The fish, described recently in the journal Cave and Karst Science, may still be in the process of evolving to be a separate new species, says Harries, a study co-author—and could present scientists with a unique opportunity to understand this evolutionary process.The finding raises many questions, such as how the fish maintain their body size, what they feed on, and how they’ve adapted to live in these caves, which are extremely extensive and deep, many of which haven’t yet been explored. “I was amazed how big they were.”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 color—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. (Learn more: How this rare, good-luck fish is thriving in Bhutan.)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.