This fish could expand what we know about one of the oddest deep-sea ecosystems

Off the Pacific coast of Costa Rica sits a deep chimera of an ecosystem. Jacó Scar is methane, where steam escapes from sediments into seawater, but the dust is not cold like others found before. But the geochemical activity gives the warm scalar water that gives organisms on either side of the cooler volatile and burning hydrothermal vents that they call home.

One scarce inhabitant is a species of recently discovered small, purple fish, called the eelpout, first described on January 19th. Zootaxa. This fish is the first vertebrate species found at Scaram and could help scientists understand how the unique ecosystem looks.

Jacó Scar was discovered during the exploration of a known methane field off the Costa Rican coast and was named for the nearby town of Jacó. It’s a “really diverse place” with many different organisms living in a variety of microhabitats, says Lisa Levin, a marine ecologist at the Writers Institution of Oceanography in La Jolla, Calif.

Levinus was in one of the first expeditions to Scaram but was not in the new study. He mentions the team finding and collecting one fish on this first excursion, but the researchers did not recognize it as a new species.

A few more specimens were subsequently snagged among the submersibles. Charlotte Seid, an invertebrate biologist at Scripps who works on spotting organisms found in Costa Rican seeps, took the fish to ichthyologist Ben Frable, also of Scripps, for formal identification.

Frable says he knew the fish was an eelpout. They look exactly as one would expect from their name: like twisted eels, although they are not real eels. But he was working hard. Eelpouts are a diverse family of fish from about 300 species that can be found all over the world in various depths of the ocean.

While the physical differences between species can be subtle, they are “kind of a tricky group” to identify, says Frable. “I’m just not really getting anywhere.” So the team turned to eelpout expert Peter Rask Møller at the Copenhagen Museum of Natural History in Denmark, sent him X-rays, pictures and finally one of the fish specimens.

Møller’s enigmatic eelpout to narrow down the genre Pyrolycus“Fire wolf.” It turned out to be a tool, called a dichotomous key, that Frable had used to make earlier samples of samples. Pyrolycus was described in 2002, “I didn’t know that kind of thing,” says Frable.

Because two other notes Pyrolycus The species live far in the western Pacific and have a variety of body features, called a team of mystery fish P. lie — a new species.

At first, most eels evolved in cold waters, says Frable, but many have since made their home in hot hydrothermal waters. Of the 24 known species of fish that live only in hydrothermal vents, 13 of them are eels, says Frable.

The new discovery questions how it was known Pyrolycus species live so far apart. It may be related to the fact that methane is often more common than before in the ocean floor, and if some are warm like Jacó Scar, new species could use them as refuges moving east.

And comparing P. lie by breathing with their relatives, researchers may be able to tell how they adapted to live in the warm waters of the Scar – which may provide clues as to how other species have managed to live there as well.

Eelpout is part of a mixture of other species that form the complex ecosystem of Jacó Scar, along with, for example, clams typically found on cold rocks and bacteria found at hydrothermal vents. Jacó Scar is a “mixture” of species found in other parts of the world, Seid says. Figuring out how this eclectic bunch interacts is “part of the fun.”