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10 Chambered Facts About Nautiluses

Half a billion years before the first submarine left harbor, the ancestors of our modern nautiluses were already beginning to master the art of buoyancy control. How do these creatures work? Read on.

1. THERE ARE SIX RECOGNIZED SPECIES.

The chambered nautilus (Nautilus pompilius) is hands-down the most famous of these cephalopods. The orange-banded creature shares its genus with three other species, known as the Palau, bellybutton, and white-patch nautiluses (with a potential fourth, Nautilus repertus, though most scientists believe it's actually a large chambered nautilus). Meanwhile, the lesser-known Allonautilus genus contains two rarely-seen species—one of which we’ll discuss later on.

With shells that measure up to 10.6 inches in diameter, chambered nautiluses are the largest of the six, and bellybuttons—whose shells max out at 6.3 inches in diameter—as the smallest. Range-wise, these animals are all restricted east-west within the waters between Samoa and the Philippines, and north-south between Japan and Australia.

2. UNLIKE ITS FELLOW CEPHALOPOD THE OCTOPUS, THE NAUTILUS HAS A POOR MEMORY.

From the meaning of certain symbols to how to open child-proof lids, an octopus can remember a lot—and retain that knowledge long-term. Nautiluses, in contrast, aren’t regarded as being very bright; in fact, until recently, it was believed that they weren’t capable of forming any memories whatsoever.

Marine biologists Robyn Cook and Jennifer Basil of Brooklyn College and the City University of New York, respectively, wondered if this assumption was true—so in 2008, the pair trained captive nautiluses to associate a flashing blue light with food. After a while, the animals reacted strongly whenever this signal came on, spreading their arms in eager anticipation. However, they stopped doing so the following day. Why? Presumably, the invertebrates had managed to forget everything they’d learned within a 24-hour period.

3. THEY’RE RELATIVELY LONG-LIVED.

Squids and octopuses don't usually live long lives—in fact, most die after just two to three years. By comparison, nautiluses look like Methuselah: 17-year-old specimens have been caught, and biologists theorize that some can surpass 20 years old.

4. THEY USE AN AMAZING BUOYANCY-CONTROL MECHANISM.

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Nautilus shells have a series of chambers connected by the siphuncle—a tube made of tissue. A newborn nautilus starts life with four chambers, adding more and more as it grows (adults have 30 on average). The chambers contain a mixture of gas and seawater, and the siphuncle regulates how much of each is present within the chambers at any given time.

If a nautilus wants to descend, the siphuncle makes that happen by pumping sodium and chlorine ions into the chambers. Extra water then enters these compartments thanks to osmosis, making the animal less buoyant, and the nautilus sinks. To reverse this process and travel upward, the siphuncle simply removes ions from the chambers, and water consequently flows into the mantle cavity. As it leaves, gas bubbles start to diffuse, which lightens the shell.

5. NAUTILUSES RELY ON JET PROPULSION.

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The mantle cavity, a funnel below the eyes and present in all cephalopods, is connected to a muscular siphon. Nautiluses move forward and backward by aiming this tube and rapidly expelling water through it.

6. NAUTILUS SHELLS IMPLODE AT A CERTAIN DEPTH. 

Nautiluses are usually found between 500 and 1000 feet below the surface, and within that range, their shells hold up quite well. But going too deep can be a fatal mistake. For chambered nautiluses, 2575 feet appears to be the limit. During one 1980 experiment [PDF], a captive specimen was subjected to the amount of pressure that it would naturally encounter at this depth. Moments later, the shell imploded, killing the creature instantly.

7. CHAMBERED NAUTILUSES HAVE UP TO 90 ARMS.

These short, clustered limbs help ensnare the fish, crabs, and carrion upon which the cephalopods dine. Speaking of mealtime, hungry nautiluses use scent to track down food because they can’t see very well (their eyes lack lenses) so their eyes are more akin to pinhole cameras, which, according to the book Animal Eyes, forces them to choose between “unusably dim or unusably blurred.”

8. NAUTILUSES USE ADHESIVES TO GRAB THINGS.

Octopuses and squids employ suckers and hooks, which nautiluses lack. Instead, their arms are coated with a sticky substance that helps ensnare prey. Tiny hairs called cilia also help form viscous pads near the appendages’ tips.

9. SOME SPECIES PROTECT THEMSELVES WITH SLIME.

“It’s really a very cool way not to get eaten,” earth scientist Peter Ward told Live Science. Last August, the University of Washington professor became the first person in 31 years to spot a rare nautilus species. Allonautilus scrobiculatus is easily recognized due to its odd defense mechanism: Thick, slimy fuzz coats the animal’s shell, making it too slippery for many fish and other predators to bite into.

10. CHAMBERED NAUTILUS EGGS ARE THE LARGEST OF ANY KNOWN CEPHALOPOD.

Most cephalopod eggs are incredibly small: Those laid by the 50-pound giant Pacific octopus, for example, are about as big as a grain of rice. Around an inch long, chambered nautilus eggs dwarf the competition. Using her tentacles, a female will (presumably) affix the eggs to a hard surface, where they’ll hatch between nine and 12 months later. 

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Big Questions
Why Do We Dive With Sharks But Not Crocodiles?
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Why do we dive with sharks but not crocodiles?

Eli Rosenberg:

The issue is the assumption that sharks' instincts are stronger and more basic.

There are a couple of reasons swimming with sharks is safer:

1. Most sharks do not like the way people taste. They expect their prey to taste a certain way, like fish/seal, and we do not taste like that. Sharks also do not like the sensation of eating people. Bigger sharks like great whites enjoy prey with a high fat-bone ratio like seals. Smaller sharks enjoy eating fish, which they can gobble in one bite. So, while they might bite us, they pretty quickly decide “That’s not for me” and swim away. There is only one shark that doesn’t really care about humans tasting icky: that shark is our good friend the tiger shark. He is one of the most dangerous species because of his nondiscriminatory taste (he’s called the garbage can of the sea)!

2. Sharks are not animals that enjoy a fight. Our big friend the great white enjoys ambushing seals. This sneak attack is why it sometimes mistakes people for seals or sea turtles. Sharks do not need to fight for food. The vast majority of sharks species are not territorial (some are, like the blacktip and bull). The ones that are territorial tend to be the more aggressive species that are more dangerous to dive with.

3. Sharks attacked about 81 people in 2016, according to the University of Florida. Only four were fatal. Most were surfers.

4. Meanwhile, this is the saltwater crocodile. The saltwater crocodile is not a big, fishy friend, like the shark. He is an opportunistic, aggressive, giant beast.


5. Crocodiles attack hundreds to thousands of people every single year. Depending on the species, one-third to one-half are fatal. You have a better chance of survival if you played Russian roulette.

6. The Death Roll. When a crocodile wants to kill something big, the crocodile grabs it and rolls. This drowns and disorients the victim (you). Here is a PG video of the death roll. (There is also a video on YouTube in which a man stuck his arm into an alligator’s mouth and he death rolled. You don’t want to see what happened.)

7. Remember how the shark doesn’t want to eat you or fight you? This primordial beast will eat you and enjoy it. There is a crocodile dubbed Gustave, who has allegedly killed around 300 people. (I personally believe 300 is a hyped number and the true number might be around 100, but yikes, that’s a lot). Gustave has reportedly killed people for funsies. He’s killed them and gone back to his business. So maybe they won’t even eat you.


8. Sharks are mostly predictable. Crocodiles are completely unpredictable.

9. Are you in the water or by the edge of the water? You are fair game to a crocodile.

10. Crocodiles have been known to hang out together. The friend group that murders together eats together. Basks of crocodiles have even murdered hippopotamuses, the murder river horse. Do you think you don't look like an appetizer?

11. Wow, look at this. This blacktip swims among the beautiful coral, surrounded by crystal clear waters and staggering biodiversity. I want to swim there!

Oh wow, such mud. I can’t say I feel the urge to take a dip. (Thanks to all who pointed this out!)

12. This is not swimming with the crocodiles. More like a 3D aquarium.

This post originally appeared on Quora. Click here to view.

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Animals
10 Filling Facts About Turkeys
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Don’t be fooled by their reputation for being thoughtless. These roly-poly birds have a few tricks up their wings.

1. THE BIRDS WERE NAMED AFTER THE COUNTRY.

The turkey is an American bird, so why does it share its name with a country on the other side of the world? Laziness, mostly. Turkish traders had been importing African guinea fowl to Europe for some time when North American explorers started shipping M. gallopavo back to the Old World. The American birds looked kind of like the African “turkey-cocks,” and so Europeans called them “turkeys.” Eventually, the word “turkey” came to describe M. gallopavo exclusively.

2. THEY NEARLY WENT EXTINCT.

By the early 20th century, the combination of overzealous hunting and habitat destruction had dwindled the turkey populations down to 30,000. With the help of conservationists, the turkey made a comeback. The birds are now so numerous that they’ve become a nuisance in some parts of the country.

3. THEY’VE GOT TWO STOMACHS.

Like all birds, turkeys don’t have teeth, so they’ve got to enlist some extra help to break down their food. Each swallowed mouthful goes first into a chamber called a proventriculus, which uses stomach acid to start softening the food. From there, food travels to the gizzard, where specialized muscles smash it into smaller pieces.

4. FEMALE TURKEYS DON’T GOBBLE.

Turkeys of both sexes purr, whistle, cackle, and yelp, but only the males gobble. A gobble is the male turkey’s version of a lion’s roar, announcing his presence to females and warning his rivals to stay away. To maximize the range of their calls, male turkeys often gobble from the treetops.

5. THEY SLEEP IN TREES.

Due to their deliciousness, turkeys have a lot of natural predators. As the sun goes down, the turkeys go up—into the trees. They start by flying onto a low branch, then clumsily hop their way upward, branch by branch, until they reach a safe height.

6. BOTH MALE AND FEMALE TURKEYS HAVE WATTLES.

The wattle is the red dangly bit under the turkey’s chin. The red thing on top of the beak is called a snood. Both sexes have those, too, but they’re more functional in male turkeys. Studies have shown that female turkeys prefer mates with longer snoods, which may indicate health and good genes.

7. THEY HAVE REALLY GOOD VISION.

Turkey eyes are really, really sharp. On top of that, they’ve got terrific peripheral vision. We humans can only see about 180 degrees, but given the placement of their eyes on the sides of their heads, turkeys can see 270 degrees. They’ve also got way better color vision than we do and can see ultraviolet light.

8. THEY’RE FAST ON THE GROUND, TOO.

You wouldn’t guess it by looking at them, but turkeys can really book it when they need to. We already know they’re fast in the air; on land, a running turkey can reach a speed of up to 25 mph—as fast as a charging elephant.

9. THEY’RE SMART … BUT NOT THAT SMART.

Turkeys can recognize each other by sound, and they can visualize a map of their territory. They can also plan ahead and recognize patterns. In other ways, they’re very, very simple animals. Male turkeys will attack anything that looks remotely like a threat, including their own reflections in windows and car doors.

10. IN THE EVENT OF A TURKEY ATTACK, CALL THE POLICE.

They might look silly, but a belligerent turkey is no joke. Male turkeys work very hard to impress other turkeys, and what could be more impressive than attacking a bigger animal? Turkey behavior experts advise those who find themselves in close quarters with the big birds to call the police if things get mean. Until the authorities arrive, they say, your best bet is to make yourself as big and imposing as you possibly can.

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