For over 20 years, researchers have been encountering a mysterious creature lurking kilometers beneath the ocean’s surface.
Now, they’ve finally uncovered its secret: it belongs to a previously unknown group of animals, never before seen in the deep sea.
Deep down, two kilometers (or 1,2 miles) below the surface, lies the bathypelagic zone—better known as the "midnight zone."
It’s the world’s largest habitat, but exploring it is no easy task thanks to the crushing pressure and complete darkness.
Despite the challenges, marine biologists from the Monterey Bay Aquarium Research Institute (MBARI) have been studying this hidden world to learn more about a truly unique animal.
In a recent study, the scientists revealed an exciting discovery: a brand-new species of nudibranch, which they’ve nicknamed the "mysterious mollusk." It’s the first nudibranch ever seen swimming in such deep waters, making it a groundbreaking find.
Exploring the Midnight Zone
The team used a high-tech, remote-operated underwater vehicle (ROV) to dive deep into the midnight zone. The ROV not only observed the creature in its natural environment but also collected samples, which were brought back to the research ship for analysis.
Using DNA testing and microscopic examination, the researchers studied these creatures in detail. They also analyzed hours of video footage captured by the ROV. Over two decades, they documented more than 130 sightings of this mysterious species at depths between 1,013 and 3,272 meters—and even deeper in some cases.
After piecing together all their findings, the team officially classified this new species and gave it the scientific name Bathydevius caudactylus.
Meet the "Mysterious Mollusk"
This fascinating nudibranch ranges from 5.6 to 14.5 cm long and has some striking features. It sports a jelly-like hood, a flat tail, and colorful internal organs. Its foot even resembles that of a snail. But it’s not just its looks that make it unique—the mollusk uses its hood to catch prey, a hunting technique researchers believe is one of a kind.
And if it feels threatened? It lights up!
The mollusk’s bioluminescence acts as a defense mechanism, a glowing warning to would-be predators.
Why This Discovery Matters
This new species sheds light on just how much life exists in the deep sea—and how much we still don’t know about it. Researchers estimate that only about a third of deep-sea species have been discovered so far.
The "mysterious mollusk" is an important piece of the deep-sea puzzle, helping scientists better understand how creatures adapt to life in such extreme environments.
The full study on Bathydevius caudactylus has been published in the scientific journal Deep Sea Research Part I.
