Many parts of Earth’s oceans remain virtually unexplored. The Pacific Ocean’s Mariana Trench—an estimated 36,201 feet deep—boasts pressures 1,000 times greater than that at sea level, and environmental conditions mirroring some of the most inhospitable planets in our solar system. This alien landscape is nearly devoid of light, oxygen, and food resources, and it’s filled with boiling-hot gasses oozing from the Earth’s core.
As extreme as deep sea habitats may sound, the more researchers look, the more unbelievable species they discover. This list highlights five of my favorite denizens of the deep, from the plethora of otherworldly creatures that call the Mariana Trench home.
1. The Ghostfish
In December 2014, biologists from the United Kingdom released footage of a new species of deep-sea snailfish filmed in the Mariana Trench five miles below sea level. This video shattered the record for the world’s deepest ocean fish. Snailfishes are well known deep-sea dwellers, with some 360 species found around the world, predominately in ocean trenches. Most snailfish resemble an overgrown tadpole with a blobby, oversized head and transparent, jelly-like streamlined body. Accustomed to life in the dark, snailfish have little use for pigment or patterning, and their lack of body structure helps them withstand the trench’s intense pressures.
As the 2014 team only caught a digital glimpse of the species, it has yet to be officially classified or named, so for now, the new type of snailfish is going by the apt nickname “ghostfish.” However, efforts are underway to actually gather a specimen via remote operated vehicles (ROVs) and equipment. Co-discoverer of the species Alan Jamieson described the fish as unique among snailfish, approximately six inches long with the head of a cartoon dog and body similar to a piece of wet tissue paper. The species also has long wing-like fins, which the team thinks may be used to pick out food from muddy sediment.
More is known about other types of deep sea snailfish, notably those studied in both the Kermadec and the Japan Trench, but on a whole, researchers have a lot left to learn about these animals’ lifecycles, behaviors, and basic biology.
2. The Barreleye Fish or Spookfish
This marine survivor looks like a perfect piece of CGI handiwork. The barreleye fish or spookfish has been found in the depths of the Pacific, Atlantic, and Indian Oceans, including locales in the Mariana Trench. Though only documented in its entirety in 2004, researchers have known of the animal’s existence since the late 1930s, but previous collection methods had ruined the most delicate, and amazing, of the creature’s anatomy.
Within the fish’s dome-shaped transparent head are two barrel-shaped tubular-eyes that face upwards, colored green by a layer of fluid that filters light from above. This allows minor illumination of prey (mostly jellies) even in the pitch dark, and protects the barreleye fish from their dinner’s stingers. What looks like eyes on this critter are in fact nostrils, and while the fish spends most of its time motionless, when it does smell or spot prey it maneuverers its tubular eyes to face forward and strikes upwards, swallowing prey whole in its toothless mouth. Researchers also think barreleye fish may be opportunistic hunters, scavenging tiny crustaceans and other jellies from the food-collecting limbs of giant siphonophores, jellies that can reach up to 130 feet in length.
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3. The Dumbo Octopus
Like the barreleye fish, the Dumbo octopus looks like an animator’s creation. But this cuddly looking critter is actually the world’s deepest-dwelling octopus, named for the floppy ear-like fins that protrude from the top of their mantle. Found between 300 and 500 meters below the surface, Dumbo octopi are thought to typically reach around 8 to 12 inches in length, but the largest Dumbo on record came in at 6 feet 32 inches long and around 13 pounds. Dumbo octopi are rather fierce predators with slightly more varied tastes than many of their peers, and they enjoy dining on copepods, isopods, bristle worms, and amphipods. Unlike most octopi, which tear and shred their meals, the Dumbo octopus swallows prey whole.
While rather comical looking, researchers think the Dumbo’s unusual mantle fins may have evolved as a way to conserve energy, helping avoid typically exhausting octopi locomotion methods like propulsion.
4. The Goblin or Vampire Shark
Take your pick—either name for this deep-sea creature is fitting.
Goblin sharks are considered to be living fossils, meaning they’ve roamed deep ocean trenches like the Mariana for millions of years unchanged from an evolutionary standpoint. These critters rely on elongated, flat snouts peppered with sensors capable of detecting even the smallest electrical currents, alerting them to the presence and movement of prey. Goblin sharks hunt by sweeping their snouts back and forth just above the ocean floor. When they spot a meal, their jaws actually launch forward from their body to encapsulate their prey. The largest goblin sharks documented were upwards of 3 meters (or almost 10 feet) in length, but scientists are still unsure what the average size of the species truly is given how few specimens exist.
5. Giant Toxic Amoebas
In my opinion, any list exploring the neatest species in an extreme environment or habitat must include at least one micro or single-celled life form. Some 200-plus species of microorganisms have been documented in the Mariana Trench, but none thus far have proven as impressive, or abundant, as the region’s giant amoeba. While typically amoeba remain fairly small, researchers have collected samples of the single-celled creatures averaging four inches in length at depths up to 6.6 miles in the Sirena Deep region of the Mariana Trench. Amoeba are thought to have superhuman powers, such as the ability to avoid heavy metal poisoning—a real problem when all you consume is essentially accumulated waste—by concentrating high levels of heavy metals like lead and uranium from trapped water droplets.
The abundance of creatures deep beneath the ocean surface is becoming more apparent to us humans with each new venture into the abyss—good news for sci-fi writers, science nerds like me, and anyone with an insatiable appetite for the unknown.