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.


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.


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.


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.


Wikimedia Commons // Public Domain

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.



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.


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.


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.”


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.


“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.


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. 

Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.

There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

How Does Catnip Work?

If you have a cat, you probably keep a supply of catnip at home. Many cats are irresistibly drawn to the herb, and respond excitedly to its scent, rubbing against it, rolling around on the floor, and otherwise going nuts. There are few things that can get felines quite as riled up as a whiff of catnip—not even the most delicious treats. But why does catnip, as opposed to any other plant, have such a profound effect on our feline friends?

Catnip, or Nepeta cataria, is a member of the mint family. It contains a compound called nepetalactone, which is what causes the characteristic catnip reaction. Contrary to what you might expect, the reaction isn’t pheromone related—even though pheromones are the smelly chemicals we usually associate with a change in behavior. While pheromones bind to a set of specialized receptors in what’s known as a vomeronasal organ, located in the roof of a cat's mouth (which is why they sometimes open their mouths to detect pheromones), nepetalactone binds to olfactory receptors at the olfactory epithelium, or the tissue that lines the mucus membranes inside a cat’s nose and is linked to smell.

Scientists know the basics of the chemical structure of nepetalactone, but how it causes excitement in cats is less clear. “We don’t know the full mechanisms of how the binding of these compounds to the receptors in the nose ultimately changes their behavior,” as Bruce Kornreich, associate director of the Cornell Feline Health Center, tells Mental Floss. Sadly, sticking a bunch of cats in an MRI machine with catnip and analyzing their brain activity isn’t really feasible, either from a practical or a financial standpoint, so it’s hard to determine which parts of a cat’s brain are reacting to the chemical as they frolic and play.

Though it may look like they’re getting high, catnip doesn’t appear to be harmful or addictive to cats. The euphoric period only lasts for a short time before cats become temporarily immune to its charms, meaning that it’s hard for them to overdo it.

“Cats do seem to limit themselves," Michael Topper, president of the American Veterinary Medical Association, tells Mental Floss. "Their stimulation lasts for about 10 minutes, then it sort of goes away.” While you may not want to turn your house into a greenhouse for catnip and let your feline friend run loose, it’s a useful way to keep indoor cats—whose environment isn’t always the most thrilling—stimulated and happy. (If you need proof of just how much cats love this herb, we suggest checking out Cats on Catnip, a new book of photography from professional cat photographer Andrew Martilla featuring dozens of images of cats playing around with catnip.)

That said, not all cats respond to catnip. According to Topper, an estimated 70 percent of cats react to catnip, and it appears to have a genetic basis. Topper compares it to the genetic variation that causes some individuals to smell asparagus pee while others don’t. Even if a cat will eventually love the smell of catnip, it doesn’t come out of the womb yearning for a sniff. Young kittens don’t show any behavioral response to it, and may not develop one until several months after birth [PDF].

But some researchers contend that more cats may respond to catnip than we actually realize. In one 2017 study, a group of researchers in Mexico examined how cats might subtly respond to catnip in ways that aren’t always as obvious as rolling around on the floor with their tongue hanging out. It found that 80 percent of cats responded to catnip in a passive way, showing decreased motor activity and sitting in the “sphinx” position, an indicator of a relaxed state.

There are also other plants that have similar effects on cats, some of which may appeal to a wider variety of felines than regular old catnip. In a 2017 study in the journal BMC Veterinary Research, researchers tested feline responses to not just catnip, but several other plants containing compounds similar in structure to nepetalactone, like valerian root, Tatarian honeysuckle, and silver vine. They found that 94 percent of cats responded to at least one of the plants, if not more than one. The majority of the cats that didn’t respond to catnip itself did respond to silver vine, suggesting that plant might be a potential alternative for cats that seem immune to catnip’s charms.

Despite the name, domestic cats aren’t the only species that love catnip. Many other feline species enjoy it, too, including lions and jaguars, though tigers are largely indifferent to it. The scent of the plant also attracts butterflies. (However, no matter what you’ve heard, humans can’t get high off it. When made into a tea, though, it reportedly has mild sedative effects.)

The reason Nepeta cataria releases nepetalactone doesn’t necessarily have to do with giving your cat a buzz. The fact that it gives cats that little charge of euphoria may be purely coincidental. The chemical is an insect repellant that the plant emits as a defense mechanism against pests like aphids. According to the American Chemical Society, nepetalactone attracts wasps and other insect predators that eat aphids, calling in protective reinforcements when the plant is in aphid-related distress. That it brings all the cats to the yard is just a side effect.

Because of this, catnip may have even more uses in the future beyond sending cats into a delighted frenzy. Rutgers University has spent more than a decade breeding a more potent version of catnip, called CR9, which produces more nepetalactone. It’s not just a matter of selling better cat toys; since catnip releases the compound to ward off insects, it’s also a great mosquito repellant, one that scientists hope can one day be adapted for human use. In that case, you might be as excited about catnip as your cat is.

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