‘World’s largest’ subterranean fish

Context

  • Systematic exploration of the Meghalayan caves has been underway for almost 30 years and hundreds of kilometres of cave passages have been explored and mapped. In a cave in a remote forested area of Meghalaya’s Jaintia Hills a research expedition found large specie of a subterranean fish (occurring under the earth’s surface).

About the fish

  • The blind fish was over 40 cm. It has not been named so far.
  • It is nearly five times the mean length (85mm/8.5 cm) for all known subterranean fish to date.
  • The only other species exceeding 300mm (30 cm) in length are eel-like Synbranchidae with nothing like the bulk of the new fish.
  • The 250-known subterranean (occurring under the earth’s surface) fish species around the world measure only around 8.5 cm on average.
  • The specialists say that possibly one (or more) populations of these fish became isolated deeper in the caves and over generations became adapted to the dark, losing their eyes in the process.

Closest resemblance

  • The experts feel that the fish species is very similar to the Golden Mahseer or the Tor Putitora, one of the most famous game fish of the Himalayan rivers.
  • Unique characters that distinguishes it from the Golden Mahseer is the lack of pigmentation, a lack of eyes and of course, its subterranean habitat – being locked in caves.
  • There are ‘normal’ Golden Mahseer in the area too but there is not much surface water (at least in the dry winter months) so fish end up in the cave pools and underground rivers.

Features of Subterranean ecosystems

  • Subterranean ecosystems are considered extreme, high-stress environments characterised by darkness, truncated food webs and food scarcity.
  • Despite this, they harbour exceptional vertebrate and invertebrate taxa (21,000+ species), many of which are evolutionarily unique, and relics of ancient fauna given their long-term isolation.
  • Many cave fish show different adaptations – some don’t have eyes, some have reduced eyes, some don’t have fins, some have weird body shapes.

Source:IE