World's largest cave fish found in Northeast India

Though the number of subterranean species of fish known on Earth is about 250, they are usually minuscule - about a few inches long - and live in a world of permanent dark and scant food.

Breaking the norm is a cavefish from an underground chamber in northeastern India that is reported to be much bigger than its ichthyological kin. The Um Ladaw Cavefish grows to nearly half a metre in length and weighs about 10 times more than any known species.

The discovery answers a few questions but raises more to replace them, especially ones pertaining to the size of the fish, their feeding habits, the way they adapted to live in these extremely extensive and deep caves - some of which have not yet been explored.

Though the creature is essentially blind and eyeless, it has an ability to sense light which is yet to be explained by science.

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Vegetation washed underground by rain has been assumed by researchers as the primary food source of these creatures, though none were visible at the time of discovery according to Harries, a hobbyist cave explorer and marine biologist at Heriot-Watt University in Edinburgh, Scotland.

The winter dry season is the only time to visit the case as the whole area floods and becomes completely inaccessible during the monsoons. Despite such knowledgeable deductions about their size and diet, how they get so large and what they feed on remains a riddle.

The two longest known subterranean fish species before this discovery were the blind swamp eel native to Mexico’s Yucátan and the blind cave eel from western Australia. Both creatures are known for their both narrow and ribbon-like physique.

Scientists have reason to believe that that the cavefish may be different enough from surface-dwelling golden mahseer to qualify as a unique species, despite the fact that they look very alike in body shape and structure.