The Deepest Fish Ever Found Lives 8 Kilometers Down

The successful observation of a snailfish at a staggering 8,336 meters in the Izu-Ogasawara Trench represents a significant milestone in deep-sea exploration. This 2023 record, set by scientists from the University of Western Australia and Tokyo University of Marine Science and Technology, surpassed the previous 2017 record of 8,178 meters in the Mariana Trench. The discovery was part of a decade-long study into the world's deepest fish populations, highlighting that trenches other than the Mariana, which is the deepest, are also incredibly rich with life. The slightly warmer waters of the Izu-Ogasawara Trench may play a crucial role in allowing life to thrive at such extreme depths.

Surviving the immense, crushing pressure at these depths, equivalent to the weight of 1,600 elephants, requires a host of remarkable evolutionary adaptations. Snailfish of the genus *Pseudoliparis* have gelatinous, scaleless bodies that are more resilient to pressure than the rigid bodies of other fish. Their skeletons are largely cartilaginous, and they lack a swim bladder. This physical structure, combined with specialized biochemistry, is key to their survival.

On a cellular level, these deep-sea dwellers have evolved unique solutions to maintain biological function. Their cell membranes are made more fluid and pressure-resistant by a higher proportion of unsaturated fatty acids. To counteract the distorting effects of pressure on proteins and enzymes, their cells contain high concentrations of a molecule called trimethylamine N-oxide (TMAO). This chemical shield allows their biological machinery to operate under conditions that would be instantly lethal to most other vertebrates, showcasing the incredible adaptability of life on Earth.