A small trench-dwelling fish is making a splash in deep-sea evolution

The Atacama Trench is a deep-sea channel that runs along the Pacific coast of Chile and Peru, South America. In 2018, an international team of scientists used free-falling “landers” to explore the trench, collecting images and samples of deep-sea creatures. The team discovered a new species of snail that is unique to the Atacama Trench and all other known fish species.

The tiny bluefish, which the team named Paraliparis selti — “selti” meaning “blue” in Kunza, the language of the indigenous people of the Atacama Desert — lives in walking areawater deeper than 6,000 meters or about 20,000 feet.

The newly discovered species is “unlike other snails from the Gadala Zone, these ultra-deep ocean regions,” says Thomas Linley, Ph.D., head of technology at Armatus Oceanic. “It has large eyes, a bright blue color and resembles other types of snails that live in shallower waters.” An article describing the team’s discovery was published in open access at Marine biodiversity.

There are approximately 15 known species of walking snails that inhabit deep-sea trenches, and more are being discovered every year. Most trenches are home to a single species of snail, but researchers have found that some trenches are home to up to three different species. These snails (Liparidae) seem to be particularly good at living deeper than other fish. “They’re not at all what we expect from a deep-sea fish,” Linley says. “I love showing people that the deepest fish in the world are actually very cute.”

The team used trait analysis, a three-dimensional X-ray technique called micro-computed tomography (micro-CT) and genetic barcoding to show that their blue a snail belongs to the genus Paraliparis. “Species of this genus are particularly abundant in the Antarctic Southern Ocean and have rarely been seen deeper than 2,000 meters,” says Johanna Weston, a postdoctoral researcher at the Woods Hole Oceanographic Institution. “We were very excited to see this result — it’s the first time this genus has been found in the walking area.”

The researchers say the new species may have evolved from cold-adapted Southern Ocean species. “This little blue fish opens up new questions about the relationship between cold temperature and high-pressure adaptations and provides new insights into how and when life evolved at depth,” says Mackenzie Gerringer, associate professor at State University of New York at Geneseo. “This is a reminder of the unique yet-to-be-discovered diversity in the deepest parts of our oceans.”

Courtesy of State University of New York at Geneseo