This shrimplike creature makes aluminum armor to survive the deep sea’s crushing pressure

Researchers first analyzed H. gigas specimens found at the bottom of the Challenger Deep, more than 10,000 meters below the surface of the ocean. They found that this extreme amphipod constructs a personal suit of armor—a layer of aluminum hydroxide gel covering the surface of its exoskeleton. But aluminum isn’t abundant in ocean water, making it hard to source as a building material. It is, however, abundant in ocean sediment.
To figure out how H. gigas accesses its aluminum, the team exposed sediment from the Challenger Deep—which the crustacean likely swallows when eating—to chemicals in its gut. Within that acidic environment, a byproduct of the plants in its typical diet reacts with the metal-rich sediment to free up aluminum ions. When these aluminum ions are released into alkaline seawater, they transform into protective aluminum hydroxide gel, the researchers report this month in PLOS ONE.