Deep-Sea Cameras Off Japan Film Mysterious Floating Creature Scientists Can’t Identify

Scientists dropped cameras about 29,900 feet deep off the coast of Japan and discovered a deep-sea creature so strange that they could not identify it.

A team led by the Minderoo-UWA Deep-Sea Research Centre at the University of Western Australia discovered the mysterious slow-gliding marine creature during a two-month expedition on the research vessel DSSV Pressure Drop. The team used high-definition cameras on the crewed submersible Limiting Factor to explore three of Japan’s deepest underwater trenches: the Japan Trench, the Izu-Ogasawara Trench, and the Ryukyu Trench.

The researchers identified 108 distinct organism groups during the mission. However, they were unable to classify one ghostly white organism seen at the bottom of a deep-sea trench. The unidentified marine animal was observed floating near the seafloor in the Ryukyu Trench in the Philippine Sea, along the eastern edge of Japan’s Ryukyu Islands, at depths of up to 29,977 feet, where pressure is nearly 1,000 times greater than at sea level.

According to a report by BBC Wildlife Magazine, the creature is currently being classified as “Animalia incerta sedis” as scientists still don’t know what it is. Despite consultations with taxonomic experts worldwide, the organism cannot be confidently assigned to any known phylum. While it shares some visual similarities with nudibranchs or sea cucumbers, its identity remains unclear.

“Initially, the authors speculated that this organism might be a nudibranch,” the researchers write in a recent study published in the Biodiversity Data Journal.

Like sea slugs, its body appeared to be divided into two symmetrical halves and featured antennae-like projections resembling a nudibranch’s rhinophores. Its pale appearance also reminded the team of the alabaster nudibranch (Dirona albolineata). But other experts were not convinced.

“Some noted that the appendages appeared too rigid to belong to a nudibranch,” write the study authors, “while others speculated that they appeared to be of ‘molluscan morphology’, but could not speculate beyond that.”

At around 29,960 feet, the sighting was more than twice as deep as the deepest known nudibranch, previously recorded at about 13,100 feet. That earlier deep-sea organism also puzzled scientists at the time and was informally dubbed the “mystery mollusc,” reports BBC Wildlife Magazine.

In addition to the unidentified creature, the research team filmed a wide range of marine life during the expedition, including carnivorous sponges, a “supergiant” scavenging amphipod, and a snailfish feeding at a record depth of 27,350 feet.