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The Weird Creatures of the Mariana Trench, Earth's Real-World Pacific Rim
The sea pigs, squishy fish, and giant cells of the Mariana trench.
The world's oceans are big and dark and deep. They cover approximately 70% of the planet’s surface and contain a huge portion of Earth’s biodiversity. If you want to find some of the weirdest organisms to ever slither, crawl, or swim, you only need to look down, down deep.
The average depth of the world’s oceans is more than 3,600 meters, approximately 2.3 miles. As you plunge beneath the surface, water molecules scatter light from the Sun, and it gets dark fast. As you dive deeper, the environment gets darker and colder as the pressure continually rises. Eventually, you’ll reach the hadal zone, named for the Greek god Hades and his underworld domain. In the western Pacific, off the coasts of Japan, the Philippines, and Papua New Guinea, near Guam and the volcanic Mariana Islands, you’ll find the deepest place on the face of our planet.
The Mariana Trench runs more than 1,500 miles long and spans more than 40 miles across. At its deepest point, known as Challenger Deep, the trench descends approximately 11,000 meters (6.8 miles) into the deep. At that depth, the water pressure is more than 1,000 times the normal atmospheric pressure on the ground and the temperatures are barely above freezing. Despite the harsh conditions of the trench, researchers have found creatures big and small living there.
What lives in the Mariana Trench?
In Guillermo del Toro’s 2013 giant monster movie Pacific Rim (streaming now on Peacock) the trench goes even deeper. At the bottom of Challenger Deep, an interdimensional rift known as the Breach opens on an alien world filled with gigantic creatures. Mega monsters called Kaiju emerge periodically and attack coastal cities. Humanity bands together to build gigantic mechanical weapons called Jaegers, controlled by a pair of mind-melded human pilots.
In Pacific Rim, our world is under constant threat of whatever emerges from the trench. In the real world, the residents of the Mariana Trench are less dangerous but just as interesting.
Mariana snailfish
The Mariana snailfish or hadal snailfish might hold the record for the deepest fish in existence. They are relatively small, with adults measuring between 4 and 11 inches long. They have semi-translucent bodies with slender tails, giving the appearance of a pale overgrown tadpole.
They can’t really see, and they don’t need to, that far from any sunlight. The Mariana snailfish lives at depths between 6,000 and 8,000 meters (3.7 to 5 miles) under the ocean’s surface. They are top predators of the hadal food web, gobbling up small crustaceans and anything else they can get their mouths around. Of course, surviving that far down requires some unique adaptations like a squishy skeleton.
Amphipods
Amphipods are an order of crustacean containing nearly 10,000 known species. They are found anywhere there is water, including in the deepest parts of the Mariana Trench. These deep dwelling crustaceans can get up to a relatively large 2 inches in length and they feed on the falling organic material (dead plants, animals, and waste) known as marine snow.
At those pressures, the calcium carbonate that makes up their shells dissolves too quickly and they’ve developed a unique adaptation to solve that problem. Recent research indicates hadal amphipods absorb aluminum ions from the seafloor and incorporate them into their shells. That provides an additional barrier, like a literal suit of metal armor, protecting the calcium carbonate from dissolving.
Translucent sea pig
The humble sea pig is a type of sea cucumber which crawls along the bottom of the deep sea, sifting through the mud and looking for morsels. Just a few inches long, the sea pig is pink in color and slender, with tube feet. It snuffles through the mud like a pig on a truffle hunt and they’ve developed a strange and mysterious relationship with baby crabs.
During one MBARI (Monterey Bay Aquarium Research Institute) expedition, baby king crabs were found clinging to the undersides of sea pigs, possibly as a means of protection. It’s unclear if the crabs provide any benefit to the sea pig, or if they are simply being used as living shields. In any event, sea pigs are an adorable and interesting addition to the ocean’s deepest neighborhood.
Giant single-celled xenophyophores
These might be the weirdest organisms in an environment filled with weird organisms. Once thought to be a kind of sea sponge, xenophyophores are now known to be a single celled organism with multiple nuclei, capable of growing to the size of a softball.
They are difficult to study because they are so fragile and researchers struggle to retrieve them from the ocean deep, intact. It’s believed that they use slime to eat detritus from the ocean sediment and they sometimes colonize bacteria to supplement their diet.
Xenophyophores use materials they extract from the environment to build an exoskeleton known as a test. Tests come in a wide range of shapes and designs, each of which might offer their own benefits for filtering and capturing food. In some of the ocean’s deepest places, these oversized single-celled organisms are the dominant life form, making for a real-world version of Pacific Rim, as long as you scale yourself down to the perspective of a cell.
Catch Pacific Rim in all of its full-sized glory, streaming now on Peacock.
