The Hadal Zone’s Squishy Survivor: How the World’s Deepest Fish Thrives Under Crushing Pressure
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By Evan Lubofsky, whoi.edu.
At the very bottom of the ocean — in the hadal zone, where pressure is 1,100 times greater than at the surface — lives a fish that looks like it has no business surviving anywhere, let alone in the most extreme environment on the planet. The hadal snailfish is translucent, soft-boned, and no bigger than a pen, yet it’s the deepest-living fish ever recorded. A new feature from WHOI’s Oceanus magazine explores how this delicate-looking creature evolved a remarkable set of adaptations that make it not just a survivor, but a top predator in one of Earth’s least understood habitats. For ocean enthusiasts, it’s a vivid reminder of how much life remains to be discovered in the deep.
As Evan Lubofsky writes for Oceanus:
Soft bones. Translucent skin. Delicate frame. All in a body about the size of a pen. It doesn’t sound like one of the deep ocean’s top predators, but with the hadal snailfish (Pseudoliparis), looks can be deceiving.
The gelatinous, fragile-looking fish — currently the deepest-known fish in the ocean — has evolved to tolerate the extreme pressure of the hadal zone, which extends from 6,000 to 11,000 meters deep (20,000 to 36,000 feet). This part of the ocean is not only frigid and sunlight-barren, but the pressure is 1,100 times greater than that of the atmosphere.
Over its 18-million-year evolutionary history, the snailfish lost its swim bladder — a gas-filled organ that couldn’t function under such pressure — and instead developed a gelatinous body that maintains buoyancy. It produces a compound called TMAO that stabilizes its proteins under extreme pressure, and it wields a powerful second set of jaws in the back of its throat for crushing the crustaceans abundant in deep-sea trenches. As WHOI deep-sea ecologist Annette Govindarajan notes, while the hadal environment is harsh for us, it is home for the snailfish — a reminder that survival doesn’t always belong to the biggest or fiercest, but sometimes to the most delicate.
