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Subterranean Fish Named ‘Gollum’ Belongs to a New Family

The freshwater fish belongs to a never-before-described taxonomic family, making it one of the biggest finds of the last decade

The Gollum snakehead is unusual among subterranean critters because it has both eyes and a colorful complexion. (Ralf Britz / Naturhistorisches Museum Bern)
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When the Gollum snakehead was discovered in 2019, it was grouped with all the other cave-dwelling, eel-like fish in the family Channidae. But much like its Middle Earth namesake, the Gollum snakehead has found itself kicked out of a family where it doesn’t fit in.

Instead, a study published last month in the journal Scientific Reports places the Gollum snakehead and another recently described species, the Mahabali snakehead, into a family all their own. A family is the descriptive category above genus and species; for example, humans share a family, Hominidae, with chimpanzees, orangutans and gorillas, Douglas Main reports for National Geographic.

Close study of the new snakeheads’ genes and anatomy revealed so many differences compared to common snakeheads that researchers placed them in a new family, Aenigmachanna. They also have a Tolkienesque common name: dragon snakeheads.

Aenigmachanna is by far the most important freshwater fish to be discovered in the 30 years I have been a student of South Asian fishes,” Rohan Pethiyagoda, who studies freshwater fish in Sri Lanka and was not involved in the study, tells Aathira Perinchery at Mongabay India.

Dragon snakeheads live in underground reservoirs, only coming to the surface when intense rainfall floods the aquifer and carries them up. Adult fish are about four inches long, with straight, thin bodies, and they propel themselves forward and back by fluttering their bodies like a banner in the wind. Unlike most underground-dwelling critters, dragon snakeheads aren’t pale and eyeless. They’re rusty red-brown and do have eyes.

Senckenberg Natural History Collections ichthyologist Ralf Britz, the lead author on the new study, tells National Geographic that the name “dragon snakehead” fits because “everyone who sees a photo of the fish is somehow reminded of a dragon.”

The researchers discovered the Gollum snakefish when co-author Rajeev Raghavan, an ichthyologist at Kerala University of Fisheries and Ocean Studies, saw images of the unfamiliar species posted on social media, reports National Geographic. The fish had washed up into someone’s backyard well in southern India’s Western Ghats region. Raghavan sent photographs to Britz, who didn’t recognize it either. The pair studied more specimens and described the species in a paper published in 2019. At first, they grouped the fish with common snakeheads.

But dragon snakeheads have a collection of characteristics that set them apart, the new study shows. They have fewer vertebrae, a shortened swim bladder, and can’t breathe air the way common snakeheads can. Genetic analysis showed that dragon snakeheads and Channidae snakeheads last shared ancestor lived 120 million years ago, during the Cretaceous period.

In that time, Channidae snakeheads have evolved into about 50 species, but it seems that dragon snakeheads haven’t evolved much at all.

Dragon snakeheads have “a whole series of primitive characteristics,” says Smithsonian National Museum of Natural History ichthyologist David Johnson to National Geographic. Those characteristics earn them the title of “living fossils,” adds Johnson, who wasn’t involved in the study.

When dragon snakeheads evolved away from other snakeheads, the land mass that’s now India had just broken away from the supercontinent Gondwana, and dinosaurs still lived on Earth, per Mongabay India. And the region where they were found is full of biodiversity. Less than a decade ago, researchers discovered a new subterranean freshwater catfish in its own taxonomical family.

“The presence of two unique endemic families of freshwater fishes in Kerala is unparalleled, and indicates the exceptional diversity and endemicity of fishes in this part of the world,” Raghavan tells the Times of India’s Deepthi Sanjiv.

Pethiygoda suggests to Mongabay India that subterranean fish may have an advantage when disasters like the extinction event that wiped out the dinosaurs come around. By living in a relatively stable environment, the fish haven’t needed to adapt to survive. But as more people dig wells and water their fields from the limited underground reservoir, the fish may become threatened.

“It is in some ways a freshwater coelacanth,” Pethiygoda tells Mongabay India. “It also signals that new light needs to be shone on the other fishes of Kerala that seem to live in aquifers, such as Horaglanis and Kryptoglanis. Almost nothing is known of the origin of these species or their ecology.”

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