Scientists surveying a trench near Japan were surprised to find fish in one of the deepest parts of the ocean, 8,336 meters (about 5 miles) below sea level. and is probably the deepest fish ever discovered.
“They really can’t go any deeper,” says Alan Jamieson, a deep-sea scientist at the University of Western Australia who led the team that made the discovery. The previous record holder was a juvenile snail seen in the Mariana Trench, photographed in 2017 at a depth of 8,178 meters.
Fish withstand high pressures at extreme depths because they have compounds in their cells called osmolytes. The concentration of osmolytes increases at greater depths to keep fish cells from contracting too much under such bone-crushing pressure, but these compounds reach their maximum concentration at about 8,400 meters. That is the theoretical limit of fish physiology. “If someone finds fish deeper than this, it’s no big deal,” he says Jamieson.
Prosanta Chakrabarty, an ichthyologist and curator of fish at Louisiana State University’s Museum of Natural Science, said the fish, a member of the genus Pseudolipalis, can survive at great depths, even at pressures 800 times higher than on the surface. I am impressed with what you can do. “At that depth, everything from gas exchange for breathing to nearly every physiological function seems impossible,” he says. “I can barely swim to the bottom of the pool without my ears sticking out.”
Jamieson’s team discovered a snail at the bottom of the Izu-Ogasawara Trench near the main island of Japan in August 2022. The team used manned and unmanned underwater vehicles to explore deep-ocean trenches, connecting the Izu-Ogasawara to the Mariana Trench, the deepest in the south. The deepest part of the Japanese trench is slightly warmer than the Mariana Strait, reaching about 1.7 degrees Celsius (35 degrees Fahrenheit), Jamieson says.
Snails survive because the water temperature is high. Osmolite doesn’t do much at low temperatures, and these snails live close to the edge of their possibilities: “The difference is so subtle that it’s nothing to worry about,” Jamieson says. “But it makes a difference for marine animals.”
To film the fish, researchers aboard the DSSV Pressure Drop lowered a “lander”, an autonomous underwater vehicle equipped with cameras, lights, batteries, and weights to carry the device to the seafloor. rice field.
The researchers used a lander that carried dead fish as bait. Deep-sea crustaceans fed, and snails came to eat crustaceans. At 8,336 meters, the lander that made this discovery, she photographed a juvenile snail. The team was unable to identify the species of snail, but two of his others, of the species Pseudoliparis belyaevi, were caught in a nearby baited trap at a depth of 8,022 meters.
More than 400 species of snails are known, from shallow waters to extreme depths, and each species is adapted to its habitat, Jamieson said. “Each trench has its own snail,” he says. “Once you evolve to be able to cope with trenches, you can’t decompress to move from trench to trench.”
In an email to Scientific American, ichthyologist Dahiana Arcilla, curator of marine vertebrates at the Scripps Institute of Oceanography at the University of California, San Diego, pointed to the role technology played in the discovery. “Rover and Lander [will] We can gain a deeper understanding of the unexplored regions of our planet’s oceans,” she wrote.
