The newly described mystery mollusc Bathydevius caudactylus. (Image credit: © 2012 MBARI)
Fascinating footage shows a previously undiscovered floating sea slug that uses a large gelatinous hood to feed and glows to ward off predators.
Found at depths ranging from 3,300 to 13,100 feet (1,000 to 4,000 meters), this enigmatic slug (Bathydevius caudactylus) was the first nudibranch species ever found in the deep sea. Researchers first recorded the animal in February 2000 using a remotely operated vehicle (ROV) off the coast of Monterey Bay. Over the next 20 years, they collected data and studied it to provide the most complete description of a deep-sea creature to date.
Nudibranchs, or sea slugs, typically live and feed on the ocean floor, but a newly described bioluminescent species swims in the midnight zone, deep beneath the surface. The new species reaches a length of 5.6 inches (14 centimeters), has a huge gelatinous hood, a fringed tail, brightly colored organs visible through its translucent body, and a snail-like foot.
MBARI Researchers Discover Amazing New Deep-Water Floating Sea Slug – YouTube
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Initially, scientists could not determine what this unusual animal was and called it a “mystery mollusk.” After returning to the lab, anatomical and genetic studies confirmed that it was a nudibranch.
It is so unique compared to other known nudibranchs that researchers created a new family: Bathydevius, highlighting how this “tricky” creature fooled them with its unusual characteristics. It gets its species name, caudactylus, from the finger-like projections, or dactyls, on its tail.
“We were very surprised to learn that Bathydevius is a nudibranch, partly because it's so different from the others, but also because this is a pretty unusual habitat for a nudibranch,” Bruce Robison, a senior scientist at the Monterey Bay Aquarium Research Institute (MBARI), who oversaw the work to describe the enigmatic mollusk, told Live Science in an email.
“Most nudibranchs live on the sea floor in shallow water and feed on attached prey,” he added. “Moving into deep water and hunting free-swimming, fast-moving prey is a real challenge.”
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