This article is more than 4 years old

This article is more than 4 years old

More than 5,000ft below the surface of the ocean, in a canyon off the coast of southern California, the purple, globular creature appeared to glow under the submersible’s lights.

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“What is that?” one researcher asked, as the submersible’s camera moved over a crab to where the tiny orb hovered near a ledge.

“I’m stumped,” another replied. “I have no idea. I can’t even hazard a guess.”

“Are we going to grab it?” a third asked. The crab, startled by the submarine, scuttled toward the ledge. “Unless the crab gets it first.”

One of the crab’s spindly limbs knocked the orb, but it clung steadfast in place. A researcher guessed it could be related to plankton, the “kind that are sort of lumpy and thick like that”. Another tried “an egg sack of some sort” with “a little embryo type thing inside”.

The team trained a vacuum at the creature, ready to suction it into a storage container.

“It looks like a disco ball right now with the lasers next to it,” one scientist said. Before long, the purple mystery was transferred from the depths to the waiting ship above.

Facebook Twitter Pinterest The ‘purple orb’, possibly a species of sea slug, found near the Channel Islands off southern California. Courtesy OET/Nautilus Live

On the E/V Nautilus, an exploration ship manned by the not-for-profit Ocean Exploration Trust, the organism’s “ball sort of unfolded into two folds”, said Susan Poulton, a spokesperson for the group, in a call from the ship.

“It revealed a foot and rhinophores, which are these ear-like structures, and you see a sort of proboscis come off the back of it,” she said. “That’s when it clearly became a gastropod of some kind.”

The team now believes the 5cm organism, found in Arguello Canyon, an underwater formation just west of the Channel Islands, near Santa Barbara, is probably a variant of sea slug: mollusks that crawl with the help of a single foot and whose family includes a variety of brightly colored species that fly, dance and swim through nearly all levels of the oceans.

The organism’s strange glow was an effect of the light of the submersible, Pouton noted: the animal does not appear to be bioluminescent, like some species of deep sea life.

Facebook Twitter Pinterest The crab and the orb. Photograph: OET/Nautilus live

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Poulton said the crew believed the organism belonged to the pleurobranch group of gastropods, rather than the often brightly colored nudibranch, and may be a new species. No known species of California deep sea pleurobranch was purple, she said.

The team sent a sample to the Harvard Museum of Comparative Zoology for DNA analysis. Confirming a new species could take months, Poulton said.

Many pleurobranchids eat plankton and other microscopic life, and in general are less streamlined than their nudibranch cousins. The photo archives of the Sea Slug Forum reveal a menagerie of spotted blobs, leopard-striped slugs and flabby organisms lined with spikes and ridges.

The E/V Nautilus has spent weeks along the west coast investigating undersea life, tectonic rifts and cracks in the sea floor where methane plumes out. Most of the ocean remains unmapped, and the ship’s primary objective is to explore the depths and assist dozens of projects pitched to it by hundreds of scientists.

The crew broadcasts its explorations as live 24-hour video feeds on its site, Facebook and Twitter, and as data transmitted so biologists, geologists and archaeologists around the world can request samples or more data as needed.

Facebook Twitter Pinterest The organism unfolding. Photograph: OET/Nautilus Live

In the coming months the ship will return to active geology near Los Angeles and sail north to explore three shipwrecks. One will be that of the USS Independence, an aircraft carrier used as a target in the atomic tests at Bikini Atoll and scuttled as a radioactive hulk in 1951, off San Francisco. The Nautilus will also explore the Ituna, a luxury yacht that went down in 1920 en route to Oregon, and the wreck of a freighter, the Dorothy Windermote.

The Channel Islands marine sanctuary covers about 1,470 square miles of ocean; less than half of its sea floor has been mapped. The E/V Nautilus crew has also found whelks building egg towers, crabs dining on those eggs, formations that looked manmade but are actually natural, brooding octopus mothers and feeding sandstars.

Poulton said the slug was the first potential new species of the expedition, in contrast to a recent season at the Galapagos where “our biologists onboard were suspecting we’re finding new things every day”. But she noted that sometimes it took years for scientists to discover that samples thought mundane were in fact new species – and that the team has located several areas fertile for new research.

The crew of the Nautilus has found new methane seep sites off the coast of California, where rich communities of life thrive in unforgiving conditions. The environments are havens for rare species and coveted areas of research for microbiologists investigating the origins of life.

Alan Kuzirian, a senior scientist at the Marine Biological Laboratory at Woods Hole, Massachusetts, said that from a review of the Nautilus video, “the likelihood of it being a pleurobranchid is reasonable”.

“One cannot really distinguish any true dorsal structures like rhinophores or gills, so the Notaspidea might be a good starting place,” he added, referring to a suborder of “sidegill” sea slugs.

“You could hear on the video that someone said it had a flat foot. That helps.”