Unknown Lifeform Discovered in Ryukyu Trench Defies Classification

Researchers lowered cameras to a depth of 9,130 meters in the Ryukyu Trench and discovered an organism unlike any known to science. The creature has been provisionally classified as Animalia incerta sedis, meaning its exact position in biological taxonomy remains unknown.

The team from the Minderoo-UWA Deep-Sea Research Centre conducted a two-month expedition aboard the research vessel DSSV Pressure Drop. Using the manned submersible Limiting Factor, scientists explored three deep-sea trenches off the coast of Japan: the Izu-Ogasawara Trench, the Japan Trench, and the Ryukyu Trench.

In total, researchers recorded 108 different groups of organisms. However, one creature could not be identified.

Strange Lifeform at Extreme Depth

The pale, almost ghost-like organism was observed near the seafloor in the Ryukyu Trench, located in the Philippine Sea, at a depth of approximately 9,130 meters. At this depth, pressure is nearly one thousand times greater than at sea level.

Scientists consulted taxonomists worldwide, but none could assign the organism to any known phylum. As a result, it was temporarily placed in the category Animalia incerta sedis.

Uncertain Classification and Unique Features

Visually, the organism somewhat resembles sea slugs or holothurians. Researchers initially suspected it might be a nudibranch mollusk. Its body appears symmetrical and divided into two sections, with appendages resembling rhinophores — sensory "antennae” typical of such animals.

Its pale coloration also drew comparisons to the species Dirona albolineata. However, many experts expressed doubts, noting that the appendages seemed too rigid for a nudibranch.

Some specialists described its features as "mollusk-like morphology,” but no definitive classification has been established.

Depth Beyond Known Limits

The depth of 9,130 meters exceeds by more than double the known depth record for nudibranch mollusks, which previously stood at around 4,000 meters.

That earlier deep-sea organism also puzzled scientists and received the informal name "mysterious mollusk.”

The latest discovery highlights how much of Earth's deep oceans remains unexplored and how many unknown lifeforms may still exist in extreme environments.