I mentioned this species in my Science Sucks podcast interview with Ive Velikova, so I thought I would go a little more "in-depth" 😉.
This is one extreme fish. They can live so deep in the ocean it's mind-boggling to think about. They've been observed more than 8,000 meters below the surface in the hadal zone (named after the Greek god of the underworld, Hades). That's 26,247 feet or 5 miles! The pressure at that depth is more than enough to kill a person, but these fish manage just fine. By comparison, at sea level on land the pressure sits at 1 atm (atmpspheric pressure). Down below where the Mariana Snailfish lives, the pressure is 800atm. While I’m not sure what it would feel like to be in an area with 800 times the pressure that I’m used to, I imagine I’d be squished flat. Just to be clear, this is the deepest a fish has ever been observed just swimming around, living its life.
These fish call the deepest place on earth, Mariana Trench, home. That's where they got their name. The Trench, a U.S. Marine National Monument in the western Pacific Ocean, reaches a depth of 10,994 meters (36,070 feet), which is way deeper than the Grand Canyon. This World Heritage Site only reaches a depth of 1,829 meters (6,000 feet) at its deepest point.
To live this far down, this fish has undergone physical adaptations. It actually looks like a large (1ft/0.3m), pale, flesh colored tadpole. It has a wide, but small head and streamlined body. Their skin is thin and it’s actually possible to see through their body and observe internal organs like the liver. This odd fish doesn’t even have scales! They were first described in the scientific journal, Zootaxa, in 2017 by researchers Mackenzie E. Gerringer, Thomas D. Linley, Alan J. Jamieson, Erica Goetze and Jeffrey C. Drazen. They caught 37 specimen and retrieved them with free-falling traps. Once a specimen had been caught, they used a remote control to abandon the weights holding the trap down, allowing them to rise back to the surface.
While you might think these fish would be hard-pressed to find food to survive, they were found to be quite plump. There are also crustaceans that live at these depths and, sadly for them, they’re a favorite food of the Mariana Snailfish. They gather in groups to feed on the bounty.