The Mariana snailfish is the deepest fish collected from the ocean floor. (UW Photo)
© UW Photo
The Mariana snailfish is the deepest fish collected from the ocean floor.
They look like ghosts of the abyss, but the wispy, pinkish-white, smooth-skinned creatures at the bottom of the Pacific Ocean's Mariana Trench have a distinction of substance: They're the deepest fish ever brought up from the deep sea.

Now the species known as the Mariana snailfish has its official scientific name: Pseudoliparis swirei, a Latin-inspired designation paying tribute to Herbert Swire, a navigator on the 19th-century expedition that discovered the Mariana Trench.

A researcher at the University of Washington's Friday Harbor Laboratories played a key role in Pseudoliparis swirei's discovery. UW's Mackenzie Gerringer is the lead author of a paper on the species' discovery, published today in the open-access journal Zootaxa.

"This is the deepest fish that's been collected from the ocean floor, and we're very excited to have an official name," Gerringer, who came to UW from the University of Hawaii at Manoa, said in a news release. "They don't look very robust or strong for living in such an extreme environment, but they are extremely successful."

Gerringer was working on her Ph.D. in Hawaii and conducting research as part of an international team when 36 of the snailfish specimens were collected in 2014 near Guam, at depths ranging between 22,600 and 26,135 feet (6,900 to 7,966 meters). The researchers used free-falling traps, baited with bags of mackerel, to catch and retrieve the fish.

An additional specimen was collected during a Japanese-led expedition this January. Since then, researchers have captured video footage of Mariana snailfish swimming at depths of 26,716 feet (8,143 meters), which is the deepest sighting so far.

Scientists took a close look at the physiology of the fish and ran DNA tests to make sure the population they sampled was sufficiently distinct from other types of fish to be designated as a newfound species. They pored over CT scans made at Friday Harbor Labs to catalog the distinguishing details for their paper.

Mariana snailfish
© University of Washington Photo / Adam Summers
A CT scan shows internal details of the Mariana snailfish. The green shape, a small crustacean, can be seen in the snailfish’s stomach.
Mariana snailfish thrive in the depths of the Mariana Trench, living off tiny crustaceans and shrimp that they suck into their mouths.

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

Gerringer, who specializes in the study of snailfish, is now focusing on species that live at shallower depths off the coast of San Juan Island. But she's still intrigued by the surprising success of the deep sea's denizens.

"It's amazing to see what lives there," she said. "We think of it as a harsh environment because it's extreme for us, but there's a whole group of organisms that are very happy down there."