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Explained: A 100 million-year-old fish in Kerala, named after a Lord of the Rings character

28th October, 2020 Biodiversity

Context:  ‘Aenigmachanna gollum’ belongs to an old family of fish, called dragon snakeheads, which retains its primitive characteristics after all these millennia.

  • It looks like a dragon, swims like an eel, and has remained hidden for a hundred million years.
  • “These living fossils hold a prominent role for our understanding of the diversification of the group in question,”
  • Besides the Gollum, a sister species has also been discovered, called ‘Aenigmachanna mahabali’.

A rare sighting

  • The discovery of a new family of fish is very rare.
  • The dragon snakeheads have evaded scientists till now because they live in subterranean aquifers and come to the surface only after heavy flooding from rain.
  • The closest relative of the family Aenigmachannidae is the Channidae, of which at least 50 species can be found in the streams and lakes of Asia and tropical Africa.
  • According to molecular analyses, the two families split from each other 34 million to 109 million years ago.
  • “This may indicate that Aenigmachanna is a Gondwanan lineage, which has survived break-up of the supercontinent, with India separating from Africa at around 120 million years ago,”

Relic from another time

  • The lack of evolution can be seen in the shortened swim bladder of the dragon snakeheads as well as fewer vertebrae with ribs.
  • These indicate that the family is less specialised than regular snakeheads.
  • The family also has eyes and a reddish brown pigmentation, which is unusual as most subterranean fish are pale and have no eyes.
  • Unlike the Channidae, the Aenigmachannidae also lack the suprabranchial organ that allows the former to breathe air and proliferate widely.
  • “Among the seemingly endless diversity of animal life on our planet, a few extant species hold a unique position for our understanding of the evolution of the group to which they belong.
  • Such taxa have previously been characterized with the term ‘living fossil’ starting with Darwin or have been referred to as ‘basal taxa’.
  • They exhibit a striking level of morphological stasis as evidenced by a surprisingly large number of primitive characters compared to their extant sister group, and often represent lineages with only few extant representatives and a restricted distribution.

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  • Gollum and Mahabali would have remained unknown for longer without the power of social media.
  • The Gollum snakehead was first identified as a new species and genus in May 2019 in a study published in Zootaxa.
  • Soon after the researchers came across a single specimen of its sister, the Mahabali snakehead.

There’s more unknown

  • The researchers say that the area where Aenigmachanna was collected is part of the Western Ghats – Sri Lanka Hotspot — which is among the richest biodiversity hotspots in the world.
  • “Its high levels of endemism are not only the result of recent radiations, but also of the presence of a number of ancient lineages.
  • Especially among vertebrates there are a number of such relic lineages in the Western Ghats, often with unclear phylogenetic relationships, such as the cyprinid Lepidopygopsis and the catfish Kryptoglanis, or with remote biogeographical connections, such as the burrowing frog Nasikabatrachus,”.
  • Ten other species of subterranean fish have been discovered in the aquifers.
  • This area also services around six million wells in the region so the water table is lowering — a danger to other unknown life forms that have resided here for millennia.