Mariana Snailfish Thrives in the Depths of the Mariana Trench

In the darkness of the Mariana Trench in the western Pacific Ocean, the Mariana snailfish (Pseudoliparis swirei) has been found to inhabit depths exceeding eight kilometers, underscoring that the deep sea is far from an empty void. Introduced to the scientific world in 2017, this species was identified through analyses of its unique morphology, skeleton, tissues, eggs, and DNA. The Mariana snailfish is found in an environment where pressures are hundreds of times greater than at sea level, specifically between approximately 6,900 and over 8,000 meters deep. Contrary to the common image of deep-sea fish with large fangs, its appearance is pale, soft, and tadpole-like. However, this seemingly fragile body is a result of remarkable adaptations to its extreme habitat. The Mariana snailfish possesses incompletely ossified bones, thin muscles, and lacks a gas-filled swim bladder that could rupture under extreme pressure. Genomic studies have revealed changes in its visual system, pigmentation, bone formation, and cell membranes, which are thought to enable its survival in darkness and high pressure. While once reported as the "deepest-living fish," this record has since been surpassed. In 2023, fish from the genus Pseudoliparis were recorded at a depth of 8,336 meters in the Izu-Ogasawara Trench in Japan. This marks the deepest living fish ever documented, although the specific species has not yet been identified. Therefore, the Mariana snailfish remains significant as one of the scientifically described species inhabiting the deepest parts of the ocean. This discovery represents a significant step forward in deep-sea biology, highlighting the vast diversity and adaptability of life on Earth.