Researchers have discovered a new species in the ocean’s “midnight zone.” This mysterious mollusk has the ability to glow.
The new species, named Bathydevius caudactylus, is about the size of an apple and is classified within the group of sea slugs. However, it does not resemble any sea slug previously observed by scientists at the Monterey Bay Aquarium Research Institute (MBARI).
A Glowing Creature of the Deep
Typically, sea slugs inhabit the ocean floor or coastal environments like tidal pools. Only a few are known to live in open waters near the surface.
In contrast, Bathydevius resides in the ocean’s “midnight zone,” an area that stretches from 1,000 to 4,000 meters below the ocean’s surface. With a paddle-like tail and a large, gelatinous head, they can emit light through bioluminescence.
Bathydevius is a swimming sea slug that glows through bioluminescence – (Photo: MBARI).
Senior scientists at MBARI, Bruce Robison and Steven Haddock, first encountered Bathydevius in February 2000 during a deep dive off the coast of Monterey, using the remotely operated vehicle Tiburon. Since then, they have observed this “mysterious mollusk” over 150 times.
At first glance, Bathydevius “looks more like a large speaker with a feathery tail” than a sea slug, co-author of the study Haddock noted. It also has a structure resembling a snail’s foot. This initially led researchers to wonder exactly which type of mollusk Bathydevius belongs to.
A “Unique” Species
The underwater research robot has detected Bathydevius in the waters off the Northwest coast of North America, from Oregon to Southern California.
Researchers from the National Oceanic and Atmospheric Administration (NOAA) have also observed a similar organism in the Mariana Trench, located in the western Pacific Ocean, indicating that Bathydevius has a broader range than previously known.
The research team collected a specimen for further study in the laboratory. The anatomical and genetic structure of the specimen reveals that it is a type of sponge, but a special one that has adapted to hunt and survive in the “midnight zone.”
Nearly every aspect of Bathydevius reflects adaptation to the “midnight zone,” from anatomy and physiology to reproduction, feeding, and behavior. They move up and down in the water column by contracting their bodies or drifting with the current. They possess both male and female reproductive organs. When they need to evade predators, they rely on their translucent bodies for natural camouflage.
If threatened, Bathydevius emits light to distract its enemies. The luminous particles create a “starry” appearance on the back of Bathydevius that can be found in the tissues of this species.
The authors of the study express concern that deep-sea mining, including the extraction of materials from the ocean floor, could pose a threat to Bathydevius. A study describing this new species has been published in the journal Deep Sea Research Part I.
