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Frilled shark. Image credit: Getty

6 Bizarre Sharks That Live in the Deep Ocean

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Frilled shark. Image credit: Getty

Whether or not they deserve their notorious reputation, sharks are a common source of fear. But beachgoers shouldn’t worry about coming face-to-face with these spooky specimens—they all live at least 1000 feet below the ocean’s surface. From ghost sharks to goblin sharks, we’re here to shed light on the mysterious lives of these deep sea dwellers.

1. GREENLAND SHARK

The first part of the Greenland shark’s scientific name, Somniosus microcephalus, means “sleep,” a nod to its sluggish lifestyle. The second largest predatory shark in the ocean moves at a glacial pace of one mile per hour. The drowsy name also makes sense in the context of the effect the shark has on those who eat it. Its flesh contains the toxic substance trimethylamine oxide, and ingesting it can cause vomiting, diarrhea, convulsions, and the appearance of drunkenness (that’s why native Greenlanders call someone who’s had too much to drink “shark-sick”). The sharks are also capable of having abnormally long lives. In 2016, researchers found a specimen that had been cruising deep beneath the Arctic for the past 392 years.

2. GOBLIN SHARK

The goblin shark isn’t known for its dazzling good looks. Its defining feature is a jagged mouth of teeth that becomes even more pronounced when it launches forward from the skull to seize prey. Fortunately for anyone disturbed by its appearance, the goblin shark occupies depths up to 4265 feet where looks aren’t a priority.

A much bigger item on the species’s evolutionary agenda is finding sustenance. Food is hard to come by that far below the surface, so the species adapted by developing a relatively large mouth for trapping squid, fish, and crustaceans that pass by. They’ve long been known to Japanese fishermen (who originally named it tengu-zame after a long-nosed goblin from folktales), but much about these sharks still remains mysterious to scientists.

3. DEMON CATSHARK

Daniel Moore via Wikimedia Commons // CC BY 3.0

There are at least 32 species of demon catshark including the white ghost catshark, the smalleye catshark, and the Iceland catshark (above), but scientists still know little about their lives at the bottom of the Northeast Atlantic. The slow-moving creatures grow up to 2 feet long and feed on squid and crustaceans as far as 7000 feet beneath the sea. Their flat heads and gleaming, slanted eyes earned them their demonic name. Another distinctive feature of the Apristurus genus are the two spineless dorsal fins poking up from the back of the body [PDF].

4. SWELL SHARK

Not much light reaches the water 1640 feet beneath the ocean’s surface, but swell sharks have developed a unique way to catch each other’s eyes. Their skin absorbs what little blue light there is at the bottom of the sea and transforms it into brilliant green biofluorescent light. Swell sharks have a photoreceptor in their eyes that lets them detect the glow, whereas humans cannot.

A couple of years ago, a team of researchers found their way around this by building a camera with a blue light-blocking yellow filter. This allowed them to explore underwater environments with “shark vision.” Scientists aren’t entirely sure what function the biofluorescence serves, but they suspect it’s used as a form of communication between sharks. Swell sharks have a different super power for dealing with enemies: When threatened, they suck in large gulps of water, swelling up to twice their size (hence the name).

5. COOKIE CUTTER SHARK

Jennifer Strotman via Wikimedia Commons // Public Domain

This shark got its cutesy name from a rather gruesome behavior: When feeding, the 16- to 22-inch predators latch onto prey with suction cup lips and rotate to carve out medallions of meat. The wounds they leave behind are more scoop-like than cookie-shaped, and are inflicted on larger animals like marlin, tuna, wahoo, dolphins, and whales. They can be found 3200 feet deep during the day, but they wander upward at night to hunt, which has led to at least one attack on a human swimmer. Though a run-in with a cookie cutter likely wouldn’t be deadly, their creepy, tooth-filled “smile” isn’t something you'd want to see on a midnight swim.

6. FRILLED SHARK

Frilled sharks have been around for 80 million years, a fact that’s easier to process once you take a look at them. At the end of their prehistoric bodies is a mouth full of 300 teeth across 25 rows that glisten white to lure in prey.

The shark is named for its six pairs of gills which are each trimmed with red “frills.” In 2007, a group of fishermen made history when they spotted a live frilled shark in shallow waters off the coast of Japan. The fish was taken to the Awashima Marine Park in Shizuoka where it was transferred to a seawater pool. After some incredibly rare photographs were taken, the shark sadly died a few hour later.

BONUS: GHOST SHARK

In 2009, scientists with the Monterey Bay Aquarium Research Institute recorded video of a strange creature 6700 feet deep into the Gulf of California. It had a long nose, ghoulish gray skin, and saucer-like eyes that stared blankly into the surrounding abyss. Seven years later, a team of experts identified the creature to be a pointy-nosed blue chimaera, a species of ghost shark never before caught live on tape.

Despite its name, the ghost shark isn’t technically a shark. Chimaeras are close relatives that also use flexible cartilage in place of solid bone. Little is known about the group, but researchers suspect the lines of dots dimpling their snouts are used to detect prey. Males are also notable for wielding retractable sex organs on their foreheads.

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Big Questions
Why Don't We Eat Turkey Tails?
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Turkey sandwiches. Turkey soup. Roasted turkey. This year, Americans will consume roughly 245 million birds, with 46 million being prepared and presented on Thanksgiving. What we don’t eat will be repurposed into leftovers.

But there’s one part of the turkey that virtually no family will have on their table: the tail.

Despite our country’s obsession with fattening, dissecting, and searing turkeys, we almost inevitably pass up the fat-infused rear portion. According to Michael Carolan, professor of sociology and associate dean for research at the College for Liberal Arts at Colorado State University, that may have something to do with how Americans have traditionally perceived turkeys. Consumption was rare prior to World War II. When the birds were readily available, there was no demand for the tail because it had never been offered in the first place.

"Tails did and do not fit into what has become our culinary fascination with white meat," Carolan tells Mental Floss. "But also from a marketing [and] processor standpoint, if the consumer was just going to throw the tail away, or will not miss it if it was omitted, [suppliers] saw an opportunity to make additional money."

Indeed, the fact that Americans didn't have a taste for tail didn't prevent the poultry industry from moving on. Tails were being routed to Pacific Island consumers in the 1950s. Rich in protein and fat—a turkey tail is really a gland that produces oil used for grooming—suppliers were able to make use of the unwanted portion. And once consumers were exposed to it, they couldn't get enough.

“By 2007,” according to Carolan, “the average Samoan was consuming more than 44 pounds of turkey tails every year.” Perhaps not coincidentally, Samoans also have alarmingly high obesity rates of 75 percent. In an effort to stave off contributing factors, importing tails to the Islands was banned from 2007 until 2013, when it was argued that doing so violated World Trade Organization rules.

With tradition going hand-in-hand with commerce, poultry suppliers don’t really have a reason to try and change domestic consumer appetites for the tails. In preparing his research into the missing treat, Carolan says he had to search high and low before finally finding a source of tails at a Whole Foods that was about to discard them. "[You] can't expect the food to be accepted if people can't even find the piece!"

Unless the meat industry mounts a major campaign to shift American tastes, Thanksgiving will once again be filled with turkeys missing one of their juicier body parts.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
10 Juicy Facts About Sea Apples

They're both gorgeous and grotesque. Sea apples, a type of marine invertebrate, have dazzling purple, yellow, and blue color schemes streaking across their bodies. But some of their habits are rather R-rated. Here’s what you should know about these weird little creatures.

1. THEY’RE SEA CUCUMBERS.

The world’s oceans are home to more than 1200 species of sea cucumber. Like sand dollars and starfish, sea cucumbers are echinoderms: brainless, spineless marine animals with skin-covered shells and a complex network of internal hydraulics that enables them to get around. Sea cucumbers can thrive in a range of oceanic habitats, from Arctic depths to tropical reefs. They're a fascinating group with colorful popular names, like the “burnt hot dog sea cucumber” (Holothuria edulis) and the sea pig (Scotoplanes globosa), a scavenger that’s been described as a “living vacuum cleaner.”

2. THEY'RE NATIVE TO THE WESTERN PACIFIC OCEAN.

Sea apples have oval-shaped bodies and belong to the genus Pseudocolochirus and genus Paracacumaria. The animals are indigenous to the western Pacific, where they can be found shuffling across the ocean floor in shallow, coastal waters. Many different types are kept in captivity, but two species, Pseudocolochirus violaceus and Pseudocolochirus axiologus, have proven especially popular with aquarium hobbyists. Both species reside along the coastlines of Australia and Southeast Asia.

3. THEY EAT WITH MUCUS-COVERED TENTACLES.

Sea cucumbers, the ocean's sanitation crew, eat by swallowing plankton, algae, and sandy detritus at one end of their bodies and then expelling clean, fresh sand out their other end. Sea apples use a different technique. A ring of mucus-covered tentacles around a sea apple's mouth snares floating bits of food, popping each bit into its mouth one at a time. In the process, the tentacles are covered with a fresh coat of sticky mucus, and the whole cycle repeats.

4. THEY’RE ACTIVE AT NIGHT.

Sea apples' waving appendages can look delicious to predatory fish, so the echinoderms minimize the risk of attracting unwanted attention by doing most of their feeding at night. When those tentacles aren’t in use, they’re retracted into the body.

5. THE MOVE ON TUBULAR FEET.

The rows of yellow protuberances running along the sides of this specimen are its feet. They allow sea apples to latch onto rocks and other hard surfaces while feeding. And if one of these feet gets severed, it can grow back.

6. SOME FISH HANG OUT IN SEA APPLES' BUTTS.

Sea apples are poisonous, but a few marine freeloaders capitalize on this very quality. Some small fish have evolved to live inside the invertebrates' digestive tracts, mooching off the sea apples' meals and using their bodies for shelter. In a gross twist of evolution, fish gain entry through the back door, an orifice called the cloaca. In addition expelling waste, the cloaca absorbs fresh oxygen, meaning that sea apples/cucumbers essentially breathe through their anuses.

7. WHEN THREATENED, SEA APPLES CAN EXPAND.

Most full-grown adult sea apples are around 3 to 8 inches long, but they can make themselves look twice as big if they need to escape a threat. By pulling extra water into their bodies, some can grow to the size of a volleyball, according to Advanced Aquarist. After puffing up, they can float on the current and away from danger. Some aquarists might mistake the robust display as a sign of optimum health, but it's usually a reaction to stress.

8. THEY CAN EXPEL THEIR OWN GUTS.

Sea apples use their vibrant appearance to broadcast that they’re packing a dangerous toxin. But to really scare off predators, they puke up some of their own innards. When an attacker gets too close, sea apples can expel various organs through their orifices, and some simultaneously unleash a cloud of the poison holothurin. In an aquarium, the holothurin doesn’t disperse as widely as it would in the sea, and it's been known to wipe out entire fish tanks.

9. SEA APPLES LAY TOXIC EGGS.

These invertebrates reproduce sexually; females release eggs that are later fertilized by clouds of sperm emitted by the males. As many saltwater aquarium keepers know all too well, sea apple eggs are not suitable fish snacks—because they’re poisonous. Scientists have observed that, in Pseudocolochirus violaceus at least, the eggs develop into small, barrel-shaped larvae within two weeks of fertilization.

10. THEY'RE NOT EASILY CONFUSED WITH THIS TREE SPECIES.

Syzgium grande is a coastal tree native to Southeast Asia whose informal name is "sea apple." When fully grown, they can stand more than 140 feet tall. Once a year, it produces attractive clusters of fuzzy white flowers and round green fruits, perhaps prompting its comparison to an apple tree.

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