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15 ocean creatures that live in total darkness
By Angela Nelson,
Mother Nature Network, 10 August 2016.

What life lurks in the deepest, darkest parts of our planet's oceans? These unexplored remote areas hold secrets about animal behavior that mankind has never seen. And because there are more questions than answers about life at the bottom of the ocean, our imaginations run wild with tales of sea serpents like the Kraken or the Loch Ness Monster.

But there are very real monster-like creatures living thousands of feet below the surface (like the bigfin reef squid, top image) and they've adapted to their hostile environment over millions of years by taking on some unbelievably cool - and in some cases, scary - physical characteristics. Here are 15 rarely seen denizens of the deep.

1. Angler fish

Photo: Javontaevious/Wikimedia Commons

If this fish isn't the stuff of nightmares, we don't know what is. Most angler fish live in the dark depths of the Atlantic and Antarctic oceans as far as a mile below the surface. These carnivores are usually brown or gray and can grow up to three feet long, though most are around a foot long, according to National Geographic.

Angler fish have huge heads, big mouths and sharp teeth that make them look like something straight out of a horror film. But only females have the other physical characteristic for which this fish is known: "a piece of dorsal spine that protrudes above their mouths like a fishing pole - hence their name. Tipped with a lure of luminous flesh, this built-in rod baits prey close enough to be snatched," National Geographic reports.

2. Chambered nautilus

Photo: Manuae/Wikimedia Commons

Like octopus and squid, this gorgeous chambered nautilus is a cephalopod, meaning its "feet" (in this case tentacles) are attached to its head. Nautilus live in tropical waters extending from the Andaman Sea east to Fiji and from southern Japan to the Great Barrier Reef, according to the Smithsonian National Zoological Park. During the day, nautilus can be found up to 2,000 feet deep, but they move to shallower water at night to feed on hermit crabs and fish.

The nautilus has poor vision, and its primitive eyes have no lenses, the National Aquarium says. Its protective brown-and-white striped shell is divided into chambers with the nautilus and its 90 tentacles living in the outermost one. An adult nautilus will fill the 30 inner chambers with gas to maintain neutral buoyancy and it adds liquid to the chambers to dive.

The nautilus has been around a long time: It appeared 265 million years before dinosaurs, and it has changed very little in the last 400 million years. There used to be about 10,000 different species, but only a few remain, according to the National Aquarium.

3. Squid

Photo: Nhobgood/Wikimedia Commons

Many types of squid live in the dark ocean - giant squid, vampire squid and bigfin squid (like the one pictured above) to name a few. And some of them live waaaaaay down deep. The video below of an alien-like Magnapinna squid was filmed 7,800 feet under the surface in the Gulf of Mexico in 2007. National Geographic says vampire squid are happy to camp out 10,000 feet below the surface. And two of these whiplash squid were filmed in 2015 in a part of the Pacific Ocean so remote it had never been studied before.

While giant squid can be huge, with females growing up to 43 feet long and males 33 feet long, other squid species, like our friend the vampire squid, may measure less than a foot when fully grown.

4. Fangtooth fish

Photo: JesseClaggett/Flickr

There's no question where this fish got its name. Despite its ferocious appearance, the fangtooth is quite small - only seven inches max - and has been found at more than 16,000 feet deep in tropical and temperate water worldwide, according to Oceana.

Unlike other deep sea fish, this one doesn't sit and wait for prey to pass by. It actively seeks out food and ensnares it easily with its large mouth and long teeth.

5. Cookiecutter shark

Photo: JSUBiology/Flickr

This terrifying mouth belongs to the cookiecutter shark, which gets its name from the circular-shaped chunks of flesh it removes from its victims. A horrifying visual, yes, but these sharks are actually parasites, which means they harm - but do not kill - other fish or marine mammals.

As far as sharks go, these are on the smaller side, measuring up to 19 inches. They prefer warm water and live in oceans near the equator at depths of 1,000 feet.

Previously, cookiecutter sharks were called cigar sharks for two reasons: First, their bodies are long and cylindrical like a cigar, and second, they have a dark collar around their gills that looks like the band on a cigar.

6. Viperfish

Photo: Francesco Costa/Wikimedia Commons

This predator is another deep-sea fish with a large mouth, a giant lower jaw and fang-like teeth. Like the angler fish, viperfish have a light-producing organ that they dangle near their bodies to attract prey. And if that lure doesn't work, these fast swimmers rush their victims and impale them on teeth so long they don't fit in their mouth.

This foot-long fish comes in a variety of colors from green to silver to black to blue and lives about 5,000 feet below the surface during the day. According to one report, researchers believe these creatures live 15 to 30 years in the wild, but in captivity they only survive a few hours.

7. Frilled shark


The frilled shark is often called a "living fossil," according to National Geographic, because it has changed very little over the last 80 million years and still bears a resemblance to sharks that occupied oceans during the time of the dinosaurs. These deep-sea dwellers are rarely seen because they live about 4,000 feet underwater. And two frilled sharks that did make it to the surface - one in Japan in 2007 (pictured above) and another in Australia in 2015 - both died within hours of being caught.

Frilled sharks have an eel-like body with 25 rows of teeth - about 300 teeth in total - and can grow to five or six feet long.

8. Lanternfish

Photo: NOAA's Fisheries Collection/Wikimedia Commons

With at least 240 species, there are many different kinds of lanternfish. The patterns created by tiny light organs on their head, tail and underside distinguish each species, reports Britannica. These tiny swimmers are only one to six inches long and live about 1,000 feet deep in waters worldwide. Lanternfish are an important part of the food chain as prey to animals like squid and penguins.

9. Giant spider crab

Photo: sigusr0/Wikimedia Commons

The largest known crab species, the giant spider crab can have a leg span of 12 feet, a body 16 inches across and can weigh around 40 pounds. This creature is found 500 to 1,000 feet underwater in Suruga Bay off the coast of Japan (where they're considered a delicacy), and each year hundreds of thousands of them migrate to Port Phillip Bay in Australia.

These massive crustaceans can live to be 100 years old, according to the Tennessee Aquarium, and they'll eat just about anything. But they're also prey for even bigger animals, like squid. To protect themselves, they've been known to decorate their often orange-and-white shells with sea sponges to better blend into the ocean floor.

10. Atlantic wolffish

Photo: Derek Keats/Wikimedia Commons

Atlantic wolffish are voracious predators with eel-like bodies, large teeth, big heads and powerful jaws that they use to eat hard-bodied prey such as sea urchins, crabs and snails. They prefer the cold waters of the northern Atlantic Ocean, according to Oceana, where a natural antifreeze compound in their blood prevents it from freezing even at 1,500 feet underwater. Like eels, they favor rocky ocean bottoms and seaweed beds where they can hide.

These solitary fish grow up to five feet long and can weigh as much as 40 pounds, the National Oceanic and Atmospheric Administration (NOAA) says. While the wolffish pictured above is blue, they also may be a purplish brown or dull olive green.

If by any chance you see one or manage to reel one in while fishing, watch out: "When hauled out of the water it snaps like a bulldog and with good aim at anything in its way, the hands, an oar, or at other fish among which it is thrown, and it can inflict a serious bite," reports the Gulf of Maine Research Institute, which adds that they've received reports of wolffish swimming into shallower rocky waters and making a "furious attack" on people wading there.

11. Bluntnose sixgill shark


These bottom-dwelling sharks have powerful bodies, broad heads and fluorescent blue-green eyes. And they're big. The Shark Research Institute reports they can be up to 15 or 16 feet long and weigh 1,300 pounds. It takes a lot of food to fuel that body. What's on the menu? Dolphinfish, billfish, flounder, cod, hagfish, lampreys, chimaeras, rays, dogfish and prickly sharks, according to the Florida Museum of Natural History.

This highly migratory shark is found all over the world at depths of 6,000 feet, though it will move to shallower water to feed. Sixgill sharks range in color from gray to tan to black on their backs, but they're all lighter underneath.

Fun fact about these predators courtesy of the Washington Department of Fish and Wildlife: Females will migrate to shallow water when they give birth, during which their litter size ranges from 22 to 108 pups!

12. Giant tube worms

Photo: NOAA Okeanos Explorer Program/Wikimedia Commons

Communities of giant tube worms form in the Pacific Ocean around hydrothermal vents - fissures on the ocean floor that spout scalding, acidic water and poisonous gas. But even in that dark, hostile environment, those swaying white tubes can grow up to 8 feet tall. They shoot up fast, too - up to 33 centimeters a year, making them the fastest growing invertebrates, according to the Smithsonian Institution. The plumes at the tips are bright red because they're filled with blood.

They have no mouth or digestive system; instead, they survive via a symbiotic relationship with the bacteria living inside them. As Oceanus Magazine reports: "Bacteria live inside the tube worms’ bodies in a remarkable organ called a trophosome. In exchange for a fertile place to live, the bacteria convert carbon dioxide into organic carbon by using chemical energy - much the way chloroplasts provide nutrition for plants via photosynthesis using the sun’s energy."

Scientists first discovered giant tube worms in 1977 off the coast of the Galapagos Islands in the Galapagos Rift, some 8,000 feet down.

13. Oarfish

Photo: Katia Cao/Wikimedia Commons

These long deep-sea fish are said to have been the inspiration for tales of "sea serpents" through the years. And looking at this one that washed up on a beach in Mexico, it's easy to see why. The world's longest bony fish can grow up to 56 feet long and weigh 600 pounds, according to National Geographic. (It took more than a dozen U.S. servicemen to lift this 23-footer in 1996.) They're rarely seen, as they're thought to live about 3,000 feet down.

Found all over the world, these fish aren't sought for their meat. (NOAA calls it "flabby and gooey.") And instead of scales, they have tubercles covered in a material called guanine. When they come to the surface, their skin becomes soft and easily damaged.

14. Squat lobster


Lobsters are bottom dwellers no matter the depth, but some species, like squat lobsters, live up to 4,600 feet underwater. Such deep-sea lobsters are often blind and usually soft; squat lobsters don't carry shells on their backs. Instead they squeeze into crevices, often in deep-sea coral, to protect their body and leave their claws exposed, according to the Monterey Bay Aquarium.

These scavengers, which grow to just a few inches long (though their arms can be several times their body length), are more closely related to crabs than other lobsters, the aquarium says. And when thousands of them washed ashore in Newport Beach, California, in 2015, people at first mistook them for crabs.

See how its body looks to be covered in tiny hairs? It's not the only fuzzy crustacean of the deep. Another is the yeti crab - a white, hairy, small crab that lives 2,600 feet down near hydrothermal vents off Antarctica.

15. Jellyfish

Photo: Jim G/Flickr

Many species of jellyfish are denizens of the deep - crown jellyfish, the bloodybelly comb jelly, black sea nettles (pictured above), Atolla jellyfish, Narcomedusae and this previously unknown glowing jellyfish just discovered in May 2016 near the Mariana Trench. While these jellyfish may be colorful, that color is nearly invisible in the dark waters where they live.

Jellyfish are found around the world, in cold and warm water, shallow and deep. Their bodies are 95 percent water, and they have no brains.

Top image: Bigfin Reef Squid (Sepioteuthis lessoniana) at Sunshine 60 Aquarium, Tokyo. Credit: George Berninger Jr./Wikimedia Commons.

[Source: Mother Nature Network. Edited. Some images added.]