10 Eye-Popping Facts About Mantis Shrimp

iStock
iStock

"Beautiful" and "deadly" are two descriptors you don’t typically see attached to shrimp. But the mantis shrimp is in a class of its own. This colorful specimen has earned a reputation for being one of the most fearsome creatures of the deep. Here are 10 facts worth knowing about the pint-sized bruisers.

1. THEY’RE NOT SHRIMP.

iStock

Despite their namesake and relatively puny stature, mantis shrimp aren’t shrimp at all. (Neither, of course, are they mantises.) They're stomatopods, distant relatives to crabs, shrimp, and lobsters.

2. THEY PACK A POWERFUL PUNCH.

The peacock mantis shrimp (Odontodactylus scyllarus) uses two appendages called dactyl clubs to pummel its prey like aquatic Rock 'Em Sock 'Em Robots—that is, if kids’ toys could punch fast enough to boil water and split fingers to the bone. These wrecking ball "fists" spring forth from their bodies at 50 mph, accelerating quicker than a .22-caliber bullet. At those speeds, the water surrounding them briefly reaches the temperature of the Sun’s surface. When the dactyl clubs hit their target, they deliver 160 pounds of force, smashing through shells like a lightning-fast crab mallet.

3. THERE ARE HUNDREDS OF SPECIES.

Mantis shrimp come in a variety of species, and we’re aware of about 550 of them. Stomatopods from different species range in size from smaller than an inch to longer than a foot. They’re usually classified by murder method—either smashing, as detailed above, or spearing. In place of dactyl clubs, spearers have two sharp appendages on the front of their bodies built for harpooning prey. Spear-wielding mantis shrimp don’t move as fast as their club-fisted counterparts (their strikes are about 10 times slower), but the threat of death by impalement is intimidating on its own.

4. THEIR VISION IS UNPARALLELED.

iStock

Peacock mantis shrimp have the most complex set of peepers in the animal kingdom. Each eye contains 12 photoreceptors that allow them to sense different types of color. For comparison, human eyes typically contain three types of light-sensitive cells for seeing red, blue, and green. This has led some to conclude that mantis shrimp perceive the world in a psychedelic rainbow of vibrant color we can’t begin to comprehend. But in reality, the crustaceans are actually worse at differentiating between subtle variations in hue than we are.

A study from the University of Queensland found that when mantis shrimp were shown colors with a difference in wavelength less than 25 nanometers, they had trouble telling them apart. But just because mantis shrimp may not see the variations between powder blue and periwinkle doesn’t mean their vision isn’t extraordinary. On the contrary, their optic abilities are on a completely separate level from ours, functioning more like a satellite than anything found in nature. Scientists believe that mantis shrimp take all the visual information they see into their brains at once without processing it, allowing them to react to their surroundings as quickly as possible. Their independently roaming eyes and trinocular vision also make them excellent hunters.

5. THEY SHARE A SECRET LANGUAGE.

Roy Caldwell, University Of California, Berkeley

 
In addition to the all epic abilities listed above, mantis shrimp are one of the only creatures capable of seeing polarized light. This has allowed them to develop a secret code that’s undetectable to other species. The Haptosquilla trispinosa species of mantis shrimp wields feathery feeding appendages called maxillipeds that are marked with iridescent, blue spots. The cells of these features reflect light in a unique way. Instead of bouncing light into a reflective structure like the polarizing cells developed by humans, the cells distribute light across the spot’s surface. The brilliant light is plainly visible to other mantis shrimp, allowing them to signal members of their species while staying hidden from predators.

6. YOU WON’T FIND THEM IN MOST AQUARIUMS.

Prilfish via Flickr // CC BY 2.0

You’d think a mantis shrimp’s technicolor exterior would make it a staple at most aquariums, but this creature is rarely kept in captivity. The same dactyl clubs that allow them to shatter shellfish are also capable of cracking a glass tank. When aquariums do accept a ruthless specimen into their collection, it must kept behind shatterproof acrylic glass. On top of that, a captive mantis shrimp needs to be the sole occupant of its specially constructed home, lest it decides to treat its tank-mates as punching bags.

7. THEY MAKE MENACING SOUNDS.

Elias Levy via Flickr // CC BY 2.0

It’s only natural that a creature as ferocious as the stomatopod would have a threatening call to match. California mantis shrimp have been known to make low, rumbling growling sounds both in the wild and the lab. Male mantis shrimp often emit grunts at dawn and dusk, the periods of the day when they’re most likely to be hunting for food or guarding their homes. Scientists theorize that the growls are meant to attract mates and ward off competitors.

8. THEY’RE HELPING SCIENTISTS BUILD BETTER BODY ARMOR.

Jens Petersen via Wikimedia Commons // CC-BY-SA-3.0

 
The mantis shrimp’s super-powered punching abilities raise a puzzling question: How can the animal deliver such a deadly blow without injuring itself? To get to the bottom of the mystery, researchers looked at the composition of the peacock mantis shrimp’s built-in weaponry. They found that the creature’s dactyl clubs consisted of an outer coating of hydroxyapatite, a hard crystalline calcium-phosphate ceramic material. Beneath the surface lies the key to the animal’s anti-fracturing qualities. Layers of elastic polysaccharide chitin underlying the shell are positioned in a way to act as shock absorbers, reducing the possibility of cracks. The design is so effective that researchers modeled a new type of carbon fiber material after it with potential applications in aircraft panels and military body armor.

9. THEY PRACTICE SOCIAL MONOGAMY.

Barry Peters via Wikimedia Commons // CC BY 2.0

The life of a mantis shrimp isn’t all cold-blooded killing. Some species of stomatopods are known to engage in the rare practice of social monogamy, a behavior that’s especially remarkable among crustaceans. This means mantis shrimp will choose one partner to share food, shelter, and raise offspring with over the course of a lifetime. What may sound romantic to humans serves a practical purpose for mantis shrimp. Research has shown that certain mantis shrimp tend to cluster outside reefs instead of living in the heart of the action. Without the need to go looking for someone new to mate with on a regular basis, mantis shrimp couples are able to enjoy a relatively safe, sedentary lifestyle secluded from predators.

10. THEY’RE OLDER THAN DINOSAURS.

Derek Keats via Flickr // CC BY 2.0

Stomatopods began evolving independently from other crustaceans nearly 400 million years ago, about 170 million years before the first dinosaurs appeared on the scene. Since then they’ve followed an isolated, evolutionary lineage that’s resulted in some of their more unique characteristics. Their biology is so bizarre that scientists have assigned them the nickname "shrimp from Mars."

Know of something you think we should cover? Email us at tips@mentalfloss.com.

8 Surprising Facts and Misconceptions About Recycling

iStock.com/KatarzynaBialasiewicz
iStock.com/KatarzynaBialasiewicz

If you pat yourself on the back for just remembering to separate the recycling or haul that big blue bin to the curb each week, you're not alone. Despite the strides we appear to be making toward eco-consciousness as a country, we have a long way to go in helping the Earth, as evidenced by our complicated relationship with recycling. These facts about the most prevalent of the three Rs will make you pause the next time you throw anything away.

1. The United States's recycling rate is low—really low.

Figures from the Environmental Protection Agency show that America recycles about 34.7 percent of the garbage it produces. (The world's top recyclers—Germany, Austria, Wales, and South Korea—report a rate between 52 and 56 percent.) But Mitch Hedlund, founder and Executive Director of the organization Recycle Across America isn't even sure the recycling rate often quoted is accurate because there is so much junk mixed in with actual recyclables.

Recycle Across America is currently working to encourage the use of standardized labels for recycling bins to eliminate the confusion over what actually belongs in these receptacles. "If the U.S. gets the recycling number up to 75 percent, which we believe is completely possible once the confusion (over what to place in the bins) is removed, it will be the CO2 equivalent of removing 50 million cars from the roads each year in the U.S. and it will create 1.5 million permanent new jobs in the U.S. (net)."

2. Proper recycling can result in monetary savings.

Businessman stepping on green squares with recycling symbols
iStock.com/Rawpixel

While Hedlund admits the idea of providing universal labels clearly stating what should be placed in the bins is a simple one, it's making a serious impact on those who have jumped on the bandwagon. "Many schools are seeing dramatic increases in their recycling levels since using the society-wide standardized labels on their recycling bins," she says. "For instance, in the pilot program at Culver City schools in Los Angeles [County], their recycling levels doubled when they started using the standardized labels and the materials they were collecting in their recycling bins were so much less contaminated with garbage." Another story, she says, is that "as a result of a donation from Kiehls (who makes a donation to Recycle Across America each April in the sum of $50,000), all of the schools in the San Diego Unified School District and San Diego County started using the standardized labels. San Diego Unified School District reduced their landfill hauling fees by about $200,000 (net) in the first year."

3. Recent changes from China have severely impacted the recycling industry.

Until 2018, China took 40 percent of the United States's recycled paper, plastic, and metal. But in January of that year, China imposed strict new rules on the levels of contamination (think food or other garbage mixed in with the recyclables) it's willing to accept—standards American cities are largely unable to meet. Because of that, and a lack of suitable destinations closer to home, many cities have been forced to incinerate or stockpile recyclables until they can find a better solution.

4. Only 9 percent of plastic is recycled in the U.S.

The nation recycles less than 10 percent of its plastic, compared to 67 percent for paper materials, 34 percent for metals, and 26 percent for glass. And China's restrictions have especially affected plastic—while exports of scrap plastic to China were valued at more than $300 million in 2015, they amounted to $7.6 million in the first quarter of 2018, down 90 percent from the year before.

5. Clothing can be recycled, but it rarely is.

Clothing at a garage sale
iStock.com/alexeys

Unfortunately, most curbside haulers don't accept textiles, and America has a serious problem with old clothes ending up in the trash. In 2019, the nation is on track to throw away more than 35 billion pounds of textiles, according to the Council for Textile Recycling—almost double the number from 1999. On the plus side, some cities have set up drop-off points for unwanted clothes, and there are a variety of ways to sell or donate unwanted items. Some brands, including Eileen Fisher and Patagonia, have also introduced buy-back programs for their items.

6. Aluminum is the world's most-recycled packaging product.

Crushed aluminum cans
iStock.com/hroe

Nearly 70 percent of aluminum cans are recycled internationally, according to Novelis, a leader in rolled aluminum products and recycled aluminum. Aluminum is infinitely recyclable without degrading, meaning it can be reused in a way completely different from what it was in its previous life, or recast into its original form. Not only is aluminum the world's most-recycled product, it's also the most profitable and the most energy-efficient. Using recycled aluminum instead of virgin materials saves about 95% of the energy, compared to 60% for paper and 34% for glass [PDF].

7. That soda can you're drinking from could find its way back to you more quickly than you think.

According to Novelis's research, an aluminum can that is recycled can be back on a grocery store shelf within 60 days [PDF]. That's a seriously speedy turnaround.

8. Scrap recycling is big business.

While the words scrap recycling might have you humming the Sanford & Son theme song, it's far from being a junkyard industry. According to the Institute of Scrap Recycling Industries (ISRI), in 2017 U.S. scrap recyclers processed more than 130 million tons of scrap metal, paper, plastic, glass, textiles, and more—material that was sold back to industrial consumers in the U.S. and around the world, generating close to $18 billion in export sales. All told, scrap recycling was a $117 billion industry in 2017 [PDF].

This list first ran in 2015 and was updated by Mental Floss staff in 2019.

From Cocaine to Chloroform: 28 Old-Timey Medical Cures

YouTube
YouTube

Is your asthma acting up? Try eating only boiled carrots for a fortnight. Or smoke a cigarette. Have you got a toothache? Electrotherapy might help (and could also take care of that pesky impotence problem). When it comes to our understanding of medicine and illnesses, we’ve come a long way in the past few centuries. Still, it’s always fascinating to take a look back into the past and remember a time when cocaine was a common way to treat everything from hay fever to hemorrhoids.

In this week's all-new edition of The List Show, Mental Floss editor-in-chief Erin McCarthy is highlighting all sorts of bizarre, old-timey medical cures. You can watch the full episode below.

For more episodes like this one, be sure to subscribe here.

SECTIONS

arrow
LIVE SMARTER