World's Deepest Fish Formally Described For The First Time

Despite its slimy appearance in life, the fish looks fearsome in a CT scanner. Adam Summers/University of Washington

Meet the world’s deepest fish. Able to live quite happily at depths surpassing 8,000 meters (26,200 feet), this little gelatinous creature has finally been officially described, confirming that it is indeed a new species of snailfish and claiming its place in the record books.  

The fish was originally caught back in 2014, but was recorded again this year in the Mariana Trench. The footage, captured by a Japanese team, showed the odd little creature swimming around 8,134 meters (26,700 feet) below the surface, making the animal the deepest living fish known to science. Only now, however, has it been formally described in the journal Zootaxa.


Called the Mariana snailfish (Pseudoliparis swirei), its presence so far down surprised biologists, as they didn’t expect such a complex vertebrate to be able to survive the crushing pressure that far below. The animal not only survives, but seemingly thrives at such extreme depths.

The fish is not much of a looker on the surface. Mackenzie Gerringer/University of Washington

Up here on the surface, the Mariana snailfish might look like a lump of raw chicken molded into the shape of a tadpole. However, when swimming around at its preferred watery depths, it is a shimmering pearlescent creature gracefully drifting along the seafloor. It is not unusual for deep-sea animals, which have evolved under such intense pressures, to become deformed when they reach the surface.

However, the animal has a whole host of adaptations to serve it well down in the depths. The pink-white fish has soft flesh, no scales, and is so translucent that its liver is even visible through its skin. CT scans of the creature show the underlying skeleton, including their massive heads and giant teeth, which are probably used to help ensure that whatever food it does find on the seabed is unlikely to escape. 

“Snailfishes have adapted to go deeper than other fish and can live in the deep trenches,” says co-author Thomas Linley, from Newcastle University, in a statement. “Here they are free of predators, and the funnel shape of the trench means there's much more food. There are lots of invertebrate prey and the snailfish are the top predator. They are active and look very well-fed.”


Because of its incredible depth, very few people have actually explored the Mariana Trench, meaning that much of it is still completely unknown. In order to collect the 32 specimens that were described, the researchers sent remote traps with cameras into the dark, frigid waters. It takes up to four hours for the trap to sink to the bottom, and after around a day, weights are released and the machinery comes floating back to the surface.


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