Scientists have mapped only about a quarter of the ocean’s surface, leaving vast depths yet to be explored. Among these mysterious regions is the midnight zone, a dark, lightless expanse that covers 70% of the world’s waters. In this zone, researchers at the Monterey Bay Aquarium Research Institute (MBARI) recently discovered a mysterious, glowing mollusk. Named Bathydevius caudactylus, this new species features a large, gelatinous hood and a paddle-like tail that radiates brilliant bioluminescence. It is the first sea slug identified to inhabit the midnight zone. The team’s findings were published in the journal Deep Sea Research Part I on Tuesday.
The 5.6-inch-long creature is hermaphroditic and spawns on the seafloor, where it also lives. It feeds by pulling crustaceans into its funnel-shaped mouth, which is located at the back of its elastic hood. It moves through the darkness of the midnight zone by flexing its body up and down or drifting with the currents. It can even regenerate its fingerlike appendages>, called dactyls, which are used to frighten predators and distract them from its food.
Researchers have seen this creature in the deep Pacific, from Oregon to Southern California. They were able to collect a specimen for closer study in a lab. Its anatomy and genetics confirmed that it is a nudibranch or sea slug type. The scientists determined that the glowing is caused by granules throughout the animal’s body and tail. They found that if the animal loses one of its dactyls, it will regenerate in a few weeks, which they believe may be an efficient way to distract predators from eating the mystery mollusk.
CNN reported that this marine animal looks very different from any sea slug scientists have seen before. At a glance, it has a massive bowl-shaped hooded structure at one end and a flat tail that looks fringed with fingerlike projections at the other end, with colorful internal organs on display in between. At first, researchers thought it looked more like a “megaphone with a feathered tail.”
Although this marine animal is classified as a sea slug, it is unlike any sea slug scientists have ever seen. Typically, nudibranchs live along the seafloor or in coastal environments such as kelp forests and tide pools. Some are pelagic, meaning they move through open waters near the surface. The midnight zone sea slug is the first known nudibranch to move about in the abyssal waters of the midnight zone. The abyssal seafloor is much darker than the ocean’s surface, so this new species must glow to ensure predators can see it. The researchers noted that its hood also protects it from other predators. Sign up for our Wonder Theory science newsletter, which delivers intriguing news on the universe’s newest discoveries and scientific advancements. You can find us on Facebook, Twitter, and Instagram.