‘Starry’ glow in deep sea near California turns out to be ‘gelatinous’ new species
From a research vessel off the coast of California, a team of scientists watched the camera feed of a submersible robot thousands of feet underwater. Suddenly the dark waters lit up with a “starry”-looking glow.
The source? An unusual new species of deep-sea animal.
“Everyone in the control room let out a loud ‘Oooooh!’ at the same time. We were all enchanted by the sight,” Steven Haddock, a scientist with the Monterey Bay Aquarium Research Institute (MBARI), said in a Nov. 12 news release from the institute.
Researchers first encountered the bioluminescent animal about 8,500 feet down during a remotely operated vehicle (ROV) dive in 2000. They were intrigued by it immediately but had no idea what it was, nicknaming it the “mystery mollusc.”
Over the next 20 years, researchers observed the blob-like mystery animal more than 150 times during ROV dives. They spent hours watching it in its natural habitat, collected 18 specimens and analyzed its DNA, according to a study published Nov. 6 in the peer-reviewed journal Deep Sea Research Part I: Oceanographic Research Papers.
Eventually, researchers realized they’d discovered an “exceptional” sea slug: Bathydevius caudactylus.
Generally, most sea slugs “live on the seafloor” or in coastal habitats, such as “tide pools, kelp forests, and coral reefs,” the institute said. Scientifically known as nudibranchs, these slug-like animals usually crawl around slowly and eat “prey attached to the seafloor.”
But not the new species.
Bathydevius caudactylus has a “mostly transparent, gelatinous” body, “voluminous, bell-shaped” head and flat “fringed” tail, the study said. It lives in the “cold, dark realm” of the open water column, the first nudibranch known to live in such a habitat.
Photos show the sea slug, which looks more like a misshapen jellyfish than a slug. Its internal organs are brightly colored and clearly visible.
Bathydevius caudactylus moves “by flexing (its) body up and down to swim or simply drifting motionless with the currents,” the institute said. It can also “rapidly” close its hood-like head to swim backward. Its “cavernous hood” also helps in hunting and can “trap crustaceans like a Venus fly trap plant.”
A YouTube video from the institute shows the new species maneuvering through the water and emitting a blue glow. Its bioluminescence occurs when threatened and likely serves “to deter and distract hungry predators.”
Researchers also saw several Bathydevius caudactylus on the seafloor more than 9,000 feet down, where the animals “appeared to be spawning ribbons of eggs,” the study said. One “rare specimen that made it to the surface alive” repeated this spawning behavior in captivity.
Like other sea slugs, the new species is a hermaphrodite with both male and female reproductive organs. “In the vast deep-sea habitat, this strategy would maximize the chances for reproductive success,” the study said.
So far, Bathydevius caudactylus has been found off the coast of California and Oregon at depths of about 3,300 to 10,700 feet, the study said. The new species is likely more widespread.
Researchers classified the new species within a new genus, Bathydevius, and new family, Bathydeviidae, because of its distinct DNA, physical features, habitat and behavior. The name “Bathydevius” refers to its “deep-living” habitat and “caudactylus” to its “finger-like” tail fringe.
“What is exciting to me about the mystery mollusc is that it exemplifies how much we are learning as we spend more time in the deep sea,” Haddock, one of the study co-authors, said in the release.
“Deep-sea animals capture the imagination,” Bruce Robison, a scientist with MBARI and study co-author, said in the release. “Our discovery is a new piece of the puzzle that can help better understand the largest habitat on Earth.”
This story was originally published November 13, 2024 at 10:53 AM with the headline "‘Starry’ glow in deep sea near California turns out to be ‘gelatinous’ new species."
