Reddit
Reddit

18 Awesome Facts About Giant Isopods

Reddit
Reddit

There are 20 known species in the genus Bathynomus;  B. giganteus, or the giant isopod, is the biggest. Yes, they're kind of creepy looking. But they're also kind of cute! Here are a few things we know about these Internet-beloved creatures.

1. They’re not bugs.

They’re crustaceans, and are closely related to marine crustaceans like shrimp and crabs, and terrestrial crustaceans like the pillbug (Armadillidium vulgare).

2. They’re bottom dwellers.

NOAA

Giant isopods live between 550 to 7020 feet deep (and potentially deeper), and prefer a mud or clay floor, which they burrow into for shelter. “Bathynomus giganteus is more of a coldwater species,” says Dee Ann Auten, an Aquarist II at the Aquarium of the Pacific, which has four giant isopods in its Wonders of the Deep gallery. “They live in the Pacific Ocean, off Japan and in the South China Sea. That’s the kind of area where you would find them.”

3. They get big. Really big.

Reddit

Typically, giant isopods are between 7.5 and 14.2 inches in length, but they can get much bigger: One specimen pulled up with an ROV in 2010 was 2.5 feet long. Scientists aren't quite sure why these isopods get so enormous, but believe that their huge size might be an adaptation that helps them survive the extreme pressure of the deep ocean.

4. They come in different colors.

The giant isopod shell—which is comprised of overlapping segments—comes in two varieties: brown and pale lilac.

5. They’re carnivores.

Though they’re generally believed to be scavengers, feasting on dead animals that fall from above, some evidence suggests that they might also eat slow-moving live animals like sponges. Giant isopods also attack trawl catches.

6. They can go a very long time without eating.

NOAA

One giant isopod in Japan went for five years without eating a single bite before dying earlier this year. Auten attempts to feed her giant isopods every day, a ritual that requires a lot of patience. “The trick is what to feed them and how to eat them,” she says. “Here at the Aquarium of the Pacific, the hit is mackerel. It's usually what I feed them. I’ll butterfly a dead mackerel so that the insides are coming out, and then I will present it in front the isopod. I try offering food once a day and that's just because one day they might not be active as much, and one day they could be really hungry and I might miss that opportunity.”

All four of the giant isopods Auten cares for have eaten within the last year (Auten keeps track of who’s who based on the spines that are missing from their tails).  “One of them ate twice last year, one of them ate four times last year, one of them ate almost ten times last year. Another one I think was seven times,” she says. “It's fascinating and it's rewarding when you put so much effort into taking care of them and a lot of patience and you finally figure out this what they like to eat.”

7. But when they do eat, they gorge themselves.

Giant isopods have four sets of jaws—which are adapted to cut and tear at prey—and they get a workout when the animals are hungry. “When they're hungry and they're eating, definitely have a lot of food around them, because they'll keep eating,” Auten says. “They'll eat a lot at one time and then they can go for a long time without eating. There’s a comic of one giant isopod eating a dead whale, and it eats the whole thing except for the bones. It's sitting on its back like ‘ughh I'm full now.’ That's totally true! If they eat, they eat a lot.” In fact, they eat so much that they compromise their ability to move.

Still, they’re not aggressive feeders. “I've never had [an occasion] where they all ate at once,” Auten says. “I will make sure to bring enough food for all of them but whenever I feed them, it's one will eat at that one setting. They definitely would not fight.” And apparently, they’re not picky: Three giant isopods collected in the southern Gulf of Mexico had ingested large quantities of plastic.

8. They live in a constant state of semi-hibernation.

Since meals in the deep sea can be few and really far between, giant isopods limit their energy expenditure. “They have a slower metabolism,” Auten says. “Their bodies mechanics are like that because they're deep sea creatures and don’t find food all the time. So they're able to slow down their metabolism and energy level so they can survive. Watching ours, you can see they do that. They don't move around that much. They only ever move around when I'm trying to feed them. Normally they're just sitting there.”

9. They have something in common with cats.

NOAA

And it’s all in the eyes. Giant isopods have widely spaced, fixed compound eyes with more than 4000 individual facets. Cats and the crustaceans (and many other animals) have a reflective layer at the back of the eye called the tapeum, which reflects light back through the retina and increases the ability to see at night. It’s also what makes cats' and isopods' eyes appear to glow.

10. They probably don’t see all that well...

It’s pretty dark where isopods live, so, according to Auten, vision isn’t really a factor for them, or many other deep sea animals. “They use other senses to maneuver, to communicate, to find food, to find a mate,” she says. “I've done experiments with my flashlight to see if the isopods sensed a difference in light or anything like that. They don't move, they're not doing anything. Therefore, I'm thinking that maybe they might not see well.”

11. ...So They Use Their Antennae.

Giant isopods have two sets of antennae that they use to experience the environment around them. “The small antennas are used more for chemical sensing,” Auten says, “and they have large antennas that are used for physical sensing. When you put the food in front of them, you're letting them sense it, physically and chemically.” They might have a sensory receptor that responds to distortion in the water around them.

12. Want to tell males from females? Look for the peenies.

Dee Ann Auten

Female isopods have a brood pouch, or marsupium, located on their undersides, where they hold 20 to 30 eggs (top right). Males have two specialized organs: Small white appendages, called peenies (top left), that carry sperm (fun fact: smaller isopods usually have bigger peenies, according to Auten), and appendices masculinae (bottom), which they use to transfer sperm to the female. “They'll inject that sperm transfer organ anywhere within the female after she molts—because she's softer—and she's able to take on that sperm,” Auten says.

13. They have the largest eggs of all marine invertebrates.

They measure .51 inches in diameter. Females don’t eat when they’re brooding; instead, they bury themselves in sediment to reduce energy use and to protect the eggs.

14. And babies come out looking just like big isopods.

Juvenile giant isopods, or mancae, don’t have a larval stage; they’re approximately 3.4 inches long when they emerge and look exactly like adults. All they’re missing is the last pair of pereopods, or legs; when fully grown, they will have seven pairs of legs total.

15. To Grow, They Shed their Exoskeletons.

Younger isopods molt often to gain size, but “when they get older, they don't molt as much,” Auten says. “They are capable of molting, but they’ve already reached their size, so they’re not going to molt as much—or they’re not going to molt at all, because molting is only for growth.”

16. Isopods bite!

Photo courtesy Flickr user Damien du Toit; cc

“I wear gloves when I work with ours,” Auten says. “They're scavengers—they're definitely going to bite on anything. But it's a small bite, it's nothing big. They don't have big mouths.”

17. They curl up when threatened.

Auten says that isopods can potentially be eaten by anything that’s bigger than them, and when they’re threatened, they curl up into a little ball—just like their land-locked relatives, pillbugs. “If it's eating something and a fish is trying to come over and take the food from them or bite their appendages, they'll roll over to keep their food or to keep their soft organs underneath protected,” Auten says.”They would cover themselves so that nothing will attach to them. Or they'll hide in a crevasse somewhere so that nothing can find them.”

18. There’s a whole album dedicated to songs about them.

It’s called Songs About Giant Isopods, and you can listen to it here.

nextArticle.image_alt|e
iStock
arrow
Animals
14 Bold Facts About Bald Eagles
iStock
iStock

Bald eagles are powerful symbols of America—but there’s a whole lot more to these quirky birds.

1. YOUNG BALD EAGLES AREN'T BALD.

A young bald eagle with a brown head on a beach.
iStock

So obviously adult bald eagles aren't really bald, either—their heads have bright white plumage that contrasts with their dark body feathers, giving them a "bald" look. But young bald eagles have mostly brown heads. In fact, for the first four or five years of their lives, they move through a complicated series of different plumage patterns; in their second year, for instance, they have white bellies.

2. BALD EAGLES SOUND SO SILLY THAT HOLLYWOOD DUBS OVER THEIR VOICES.

A red-tailed hawk.
A red-tailed hawk's screech is usually dubbed over the bald eagle's weaker scream.
iStock

It's a scene you’ve probably seen countless times in movies and on TV: an eagle flies overhead and emits a rough, piercing scream. It's a classic symbol of wilderness and adventure. The only problem? Bald eagles don't make that sound.

Instead, they emit a sort of high-pitched giggle or a weak scream. These noises are so unimpressive that Hollywood sound editors often dub over bald eagle calls with far more impressive sounds: the piercing, earthy screams of a smaller bird, the red-tailed hawk. If you were a fan of The Colbert Report, you might remember the show's iconic CGI eagle from the opener—it, too, is making that red-tailed hawk cry. Listen for yourself and decide who sounds more impressive.

3. THEY EAT TRASH AND STOLEN FOOD.

Two bald eagles guard their prey against two magpies on a snowy field.
iStock

Picture a majestic bald eagle swooping low over a lake and catching a fish in its powerful claws. Yes, bald eagles eat a lot of fish—but they don't always catch it themselves. They've perfected the art of stealing fish from other birds such as ospreys, chasing them down until they drop their prey.

Bald eagles will also snack on gulls, ducks, rabbits, crabs, amphibians, and more. They'll scavenge in dumpsters, feed on waste from fish processing plants, and even gorge on carrion (dead, decaying animals).

4. BALD EAGLES USUALLY MATE FOR LIFE.

Two bald eagles perched on a tree.
iStock

Trash and carrion aside, they're pretty romantic animals. Bald eagles tend to pair up for life, and they share parenting duties: the male and the female take turns incubating the eggs, and they both feed their young.

5. … AND THEY LIVE PRETTY LONG LIVES.

Two bald eagles sitting on a rock.
iStock

Those romantic partnerships are even more impressive because bald eagles can survive for decades. In 2015, a wild eagle in Henrietta, New York, died at the record age of 38. Considering that these birds pair up at 4 or 5 years of age, that's a lot of Valentine's Days.

6. THEY HOLD THE RECORD FOR THE LARGEST BIRD'S NEST.

Two bald eagles in their large nest.
iStock

Bald eagles build enormous nests high in the treetops. The male and female work on the nest together, and this quality time helps them cement their lifelong bond. Their cozy nurseries consist of a framework of sticks lined with softer stuff such as grass and feathers. If the nest serves them well during the breeding season, they'll keep using it year after year. And, like all homeowners, they can't resist the thought of renovating and adding to their abode. Every year, they'll spruce it up with a whopping foot or two of new material.

On average, bald eagle nests are 2-4 feet deep and 4-5 feet wide. But one pair of eagles near St. Petersburg, Florida, earned the Guinness World Record for largest bird’s nest: 20 feet deep and 9.5 feet wide. The nest weighed over two tons.

7. FEMALES ARE LARGER THAN MALES.

Two bald eagles in their large nest.
iStock

In many animal species, males are (on average) larger than females. Male gorillas, for example, dwarf their female counterparts. But for most birds of prey, it's the opposite. Male bald eagles weight about 25 percent less than females.

Scientists aren't sure why there's such a size difference. One reason might be the way they divide up their nesting duties. Females take the lead in arranging the nesting material, so being bigger might help them take charge. Also, they spend longer incubating the eggs than males, so their size could intimidate would-be egg thieves.

If you're trying to tell male and female eagles apart, this size difference may help you—especially since both sexes have the same plumage patterns.

8. TO IDENTIFY THEM, LOOK AT THE WINGS.

A bald eagle flies across the water.
iStock

People often get excited about a big soaring bird and yell "It's an eagle!” just before it swoops closer and … oops, it's a vulture. Here's a handy identification tip. Bald eagles usually soar with their wings almost flat. On the other hand, the turkey vulture—another dark, soaring bird—holds its wings up in a shallow V shape called a dihedral. A lot of large hawks also soar with slightly raised wings.

9. THEY'RE COMEBACK KIDS.

Baby eagle chicks in a nest.
iStock

Before European settlers arrived, bald eagles were abundant across the U.S. But with settlement came habitat destruction, and the settlers viewed the eagles as competition for game and as a threat to livestock. So many eagles were killed that in 1940 Congress passed an act to protect the birds.

Unfortunately, another threat rose up at about that time. Starting after World War II, farmers and public health officials used an insecticide called DDT. The chemical worked well to eradicate mosquitos and agricultural pests—but as it traveled up the food chain, it began to heavily affect birds of prey. DDT made eagle eggshells too thin and caused the eggs to break. A 1963 survey found just 471 bald eagle pairs in the lower 48 states.

DDT was banned in the early 1970s, and conservationists began to breed bald eagles in captivity and reintroduce them in places across America. Luckily, this species made a spectacular recovery. Now the lower 48 states boast over 9700 nesting pairs.

10. THEY'RE UNIQUELY NORTH AMERICAN.

An African fish eagle flies over the water.
The African fish eagle is a relative of the North American bald eagle.
iStock

You've probably heard of America's other eagle: the golden eagle. This bird lives throughout much of the northern hemisphere. But the bald eagle is only found in North America. It lives across much of Canada and the U.S., as well as northern parts of Mexico.

Though it may be North American, the bald eagle has seven close relatives that are found throughout the world. They all belong to the genus Haliaeetus, which comes—pretty unimaginatively—from the Latin words for "sea" and "eagle." One relative, the African fish eagle, is a powerful symbol in its own right. It represents several countries; for example, it's the national symbol of Zambia, and graces the South Sudanese, Malawian, and Namibian coats of arms.

11. THEY'RE AERIAL DAREDEVILS.

A bald eagle carries a fish off in its talons.
iStock

It seems too weird to be true: While flying, bald eagles sometimes grab each other's feet and spin while plummeting to the Earth. Scientists aren't sure why they do this—perhaps it's a courtship ritual or a territorial battle. Usually, the pair will separate before hitting the ground (as seen in this remarkable set of photographs). But sometimes they hold tight and don't let go. These two male bald eagles locked talons and hit the ground with their feet still connected. One subsequently escaped and the other was treated for talon wounds.

12. THEIR EYES ARE AMAZING.

Close-up of a bald eagle's face.
iStock

What if you could close your eyes and still see? Besides the usual pair of eyelids, bald eagles have a see-through eyelid called a nictitating membrane. They can close this membrane to protect their eyes while their main eyelids remain open. The membrane also helps moisten and clean their eyes.

Eagles also have sharper vision than people, and their field of vision is wider. Plus, they can see ultraviolet light. Both of those things mean the expression "eagle eye" is spot-on.

13. THEY MIGRATE … SORT OF.

A bald eagle sits in a snowy tree.
iStock

If you're a bald eagle that nests in northern Canada, you'll probably head south for the winter to avoid the punishing cold. Many eagles fly south for the winter and return north for the summer—as do plenty of other bird species (and retired Canadians). But not all bald eagles migrate. Some of them, including individuals in New England and Canada's Maritime provinces, stick around all year. Whether or not a bird migrates depends on how old it is and how much food is available.

14. THEY CAN SWIM … SORT OF.

A bald eagle
iStock

There are several videos online—like the one above—that show a bald eagle swimming in the sea, rowing itself to shore with its huge wings. Eagles have hollow bones and fluffy down, so they can float pretty well. But why swim instead of soar? Sometimes, an eagle will swoop down and grab an especially weighty fish, then paddle it to shore to eat.

Note that the announcer in the video above says that the eagle's talons are "locked" on a fish that's too heavy to carry. In fact, those lockable talons are an urban legend.

nextArticle.image_alt|e
iStock
arrow
Animals
How Bats Protect Rare Books at This Portuguese Library
iStock
iStock

Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios