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10 Hard-Shelled Facts About Horseshoe Crabs

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The plodding sea creatures have weird blood, weirder swimming habits, and a secret weapon that’s probably saved your life.  

1. HORSESHOE CRABS ARE INCREDIBLY OLD.

Discovered in 2008, the 25 millimeter-wide Lunataspis aurora crawled over Manitoba 445 million years ago. This makes it the world’s oldest-known horseshoe crab. Four species are with us today, all of which closely resemble their long-extinct ancestors.

Supposedly frozen in time, horseshoe crabs are often hailed as “living fossils” by the media. Yet, appearances can be misleading. Evolution didn’t really leave these invertebrates behind. They’ve transformed quite a bit over the past half-billion years. For instance, some prehistoric species had limbs that split out into two branches, but today's specimens have only one.

2. THEY'RE NOT CRABS.

In fact, they aren’t even crustaceans. Unlike real crabs and their kin, horseshoe “crabs” lack antennae. So, where do the strange ocean-dwellers belong on the arthropod family tree? Biologists classify them as chelicerates, a subphylum that also includes arachnids. Members possess two main body segments and a pair of unique, pincer-like feeding appendages called chelicerae (hence the name).

3. EACH ONE HAS A HUGE ARRAY OF SIGHT ORGANS.

Rachel Oh via Wikimedia Commons // CC BY-SA 3.0

Large compound eyes rest on the sides of their shells. Come mating season, these bean-shaped units help amorous crabs locate a partner. Behind each one, there’s a small, primitive photoreceptor called a lateral eye. Towards the front of the shell are two tiny median eyes and a single endoparietal eye. On its underside, a horseshoe has two “ventral eyes,” which presumably help it navigate while swimming.

Most interesting to scientists are the compound pair. By virtue of their relatively simple wiring, they’re easy to study and have taught us a great deal about how our own eyes function.

4. BABIES CAN SWIM UPSIDE DOWN.

Walking around on the ocean floor is generally how horseshoe crabs get from point A to point B. Nevertheless, young ones will often flip over and start propelling themselves through the water, using their gills as extra paddles. With age, they do this less frequently.

5. THE SPIKED TAIL HAS SEVERAL USES.


Stinging isn't one of them, despite what many falsely believe. Among its uses are assuming rudder duties and helping the arthropod right itself after getting stuck on its back. 

6. ADULTS MAINLY EAT BIVALVES.

Both larvae and fully grown horseshoes eat aquatic worms. Though adults will also devour algae and carrion, they predominantly consume clams and mussels. When feeding time comes, these low-profile predators mash food between the spiky upper regions of their legs before pushing it into the mouth. 

7. HUNDREDS OF THOUSANDS GATHER IN DELAWARE BAY FOR A MASSIVE ANNUAL ORGY.

Every year in May and June, the bay becomes the largest Atlantic horseshoe crab spawning zone on Earth. During the night, a female will climb ashore with a male (or several) in hot pursuit. After she digs a hole and deposits her eggs, the males fertilize them. Migratory shore birds descend upon the bay in huge numbers, fattening themselves on the nutrient-rich eggs. Among these avians are scores of red knots, which use the crab fest as a final pit stop during their yearly migration from the Arctic to South America.

8. VERY FEW SURVIVE INTO ADULTHOOD.

A mother can lay as many as 90,000 eggs per clutch. Even so, it’s estimated that only about 10 of those individual embryos will ever become adults. Before they get a chance to hatch, fish, sea turtles, and birds gorge themselves on the eggs. With so many animals utterly dependent on this fodder, nesting horseshoe crabs are vital to the ecology of Delaware Bay and countless other regions around the world.   

9. ATLANTIC HORSESHOE CRAB FEMALES ARE 25 TO 30 PERCENT BIGGER THAN MALES.


When it comes to reproduction, females also mature more slowly: While males are ready to mate by age 8 or 9, their counterparts don’t start breeding until age 10 or 11. 

10. IF YOU'RE UNDER 40 AND HAVE BEEN VACCINATED, THANK A HORSESHOE CRAB.

While human beings don’t have blue blood, horseshoe crabs do. Whereas our blood uses iron-based hemoglobin to transport oxygen throughout the body, horseshoe crabs rely on hemocyanin, which contains copper. Copper turns bluish-green when it oxidizes.

Strange coloration isn’t the only remarkable thing about horseshoe crab blood. Shorelines are downright squalid: a single gram of undersea sediment contains roughly 1 billion bacteria. Unlike us, the arthropods lack infection-fighting white blood cells. Instead, special cells called amebocytes attack pathogens in the horseshoe crab's body by sealing them inside a gooey physical barrier, thus halting the malady’s spread.

Ever since Johns Hopkins University physician Frederick Bang discovered this characteristic in 1956, medical scientists have been capitalizing on it. To ensure that a vaccine or injectable drug is safe, they introduce horseshoe crab amebocytes into a sample. If the cells start releasing their goo, it’s because they’ve encountered bacteria and, therefore, the product isn’t ready yet. In the 1970s, the FDA made this test mandatory for experimental drugs and surgical implants. Without these magnificent animals, thousands—perhaps even millions—of people might have died during the past four decades from unsanitary injections.

As you might expect, horseshoe crab blood is worth a pretty penny: sellers now command $15,000 per quart. The magic elixir is extracted from over 600,000 “donors” every year, each of whom parts with 30 percent of its blood before being released within 48 hours. Sadly, though, many don’t last that long. About 10–15 percent of captured crabs die somewhere in the process, and survivors can exhibit lethargic behavior down the road. Scientists aren’t insensitive to this problem. Researchers have been trying to develop synthetic amebocytes.

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Smart Shopping
25 Dapper Outfit Choices for Fashionable Pets
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Lavishing your furry friends with adorable attire is a benefit of pet ownership that they don't mention on the adoption forms. Whether you prefer practical clothing like sweaters and jackets or statement pieces like bow ties and tutus, these dapper duds are perfect for a howl-iday or "gotcha day" gift, or simply for saying, "Who's the cutest little pupper in pajamas? You are!"

1. CASHMERE DOG SWEATER; FROM $165

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Canine Styles

This classic cable-knit cashmere sweater is a sophisticated look for Fido or Finn. Get it from Canine Styles, a luxury dog emporium in New York City that has plenty of posh and preppy outfits.

Find It: Canine Styles

2. TOGGLE DOG COAT; $85

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Canine Styles

This toggle coat (available in orange, navy, and tan) is as fashionable as it is warm. Made of Melton wool, it has Velcro closures to make getting dressed easy. It's great for long walks in the country.

Find It: Canine Styles

3. DOG TUXEDO; FROM $90

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Etsy

This satin tuxedo is perfect for the canine members of your wedding party, though it will brighten up any other occasion as well. The custom, handmade outfit comes complete with a snappy bow tie.

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4. DOG BELLE DRESS; FROM $45

Dog Belle Dress
Etsy

The queen of your castle can feel like a Disney princess in her very own version of Belle's iconic yellow dress from Beauty and the Beast. This ball gown is made from yellow crepe satin with chiffon overlay on the bodice and features hand-painted gold detailing on the skirt. Enchanted rose not included.

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5. POODLE SKIRT OUTFIT FOR DOGS; $26

Rubies Pink Fifties Girl Pet Costume
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What if you could buy a 1950s poodle skirt for your poodle? This retro dress is comprised of a pink poodle skirt, striped bodice, and sequined belt, and comes with a bow headband.

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6. RIBBED CROCHET BUNNY SWEATER; $25

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Your snuggle-bunny will look like a little fancy-pants in this ribbed crochet sweater. Choose from seven colors, including this dashing deep red.

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7. BESPOKE MONOGRAM DOG SWEATER; FROM $155

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Ruby Rufus

Bespoke clothing isn't just for humans: British luxury dog clothing brand Ruby Rufus will make your pooch a custom monogram sweater made with 100 percent Italian cashmere. You can even order it in your dog's favorite color.

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8. HOT PINK DOG TUTU; $17

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Tutus look absolutely adorable on tiny humans and animals alike. If your pooch wants to get in touch with its inner ballerina, then grab this hot pink number from Etsy. Rave reviews are a sure thing.

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9. PINK DOG POLO SHIRT; $35

Dog Pink Polo Shirt
Canine Styles

This pink polo shirt is perfect for your preppy fur baby. It features not one but a veritable multitude of crocodiles. They'll be the most dapper dog at the country club.

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10. DOG BARN COAT WITH BROWN CORDUROY COLLAR; $85

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Canine Styles

When it's time for a walk, your dog will look effortlessly chic in this fancy barn coat. It comes in navy, cranberry, orange, hot pink, and loden and features convenient pockets for anyone with opposable thumbs.

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11. WHITE PET NECK RUFF; $26

Pet Neck Ruff
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Your canine or kitty will look like their painting belongs in London's National Portrait Gallery with this Elizabethan neck ruff.

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12. CHICKEN SWEATER; $25

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Chickens can get cold when they're strutting around outside. A sweater (well, more like sweater vest) for your bird can also help prevent feather picking during molting season. Or, it can simply keep them warm while they stare pensively across a snowy landscape.

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13. PET CIRCLE SCARF; $15

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Etsy

An infinity scarf is a perfect burst of color on a dreary early morning walk. The proprietor of Mitten Made on Etsy originally designed this wool snood for her miniature Dachshund to help keep her warm during the long, cold winters in Michigan.

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14. FAB DOG TRAVEL RAINCOAT; FROM $18

Fab Dog Travel Raincoat
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This timeless yellow rain slicker will look great on any puppy when it's raining cats and dogs. It's made of 100 percent waterproof nylon shell that keeps fur dry. Bonus: It's perfect for an It Halloween costume.

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15. LACE CAT OR DOG COLLAR; FROM $10

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Etsy

This handmade, white lace collar is a must-have for fancy felines. It's also embellished with a large rhinestone.

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16. FITWARM PENGUIN PAJAMAS FOR DOGS; FROM $10

Fitwarm Cute Penguin Xmas Dog Pajamas
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Keep your pupper warm on cold winter nights with these penguin PJs. They're great for doggie sleepovers or lazy weekends on the couch watching Netflix.

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17. PLAID CASHMERE DOG COAT; FROM $225

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Your dog will look like a proper gentleman in this smart plaid peacoat. This fine garment is made of cashmere with a faux fur lining and leather buttons, and is a perfect shield against chill and fog.

Find It: Canine Styles

18. SATIN PET BOW TIE; FROM $8

Satin Bow Tie for Dog
Etsy

This satin doggie bow tie is perfect for any occasion. It comes in several colors and features a Velcro fastener that makes it easy to attach to a collar. Plus, 10 percent of every sale goes to charity: specifically to SPCA (Society for the Prevention of Cruelty to Animals) and Feeding Pets of the Homeless.

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19. RED DOG DRESS; FROM $34

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Your good boy or girl will look red carpet-ready in this elegant gown. The voluminous tulle skirt is to die for, and each bow is embellished with beads. Custom orders are also available.

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20. DOG TIE; FROM $13

Dog tie
Etsy

Your pooch will be ready to stun at any black tie event. This tie is designed like a collar, making it easy to dress your four-legged friend. This Etsy store gives back: 10 perfect of all sales are donated to an animal protection association.

Find It: Etsy

21. NAUTICAL DOG DRESS WITH MATCHING LEASH; $20

Dog sailor dress
BaxterBoo

Perfect for a day on the town or setting sail in a schooner, this is the sailor outfit you never knew your best furry friend needed. This vintage throwback also comes with a matching leash.

Find It: BaxterBoo

22. TARTAN FLANNEL PET BOW TIE; $5.50

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Etsy

Your dog or cat will turn heads in this flannel tartan bow tie. It has a convenient elastic loop that slides over your pup's collar.

Find It: Etsy

23. PUCCI DOG SHIRT; $23

dog in Pucci dog shirt
Etsy

Only the fanciest dogs wear, err, Pucci. Grab this punny "designer" t-shirt for your pup. This high-quality cotton statement piece is perfect for small breeds.

Find It: Etsy

24. PINK POLKA DOT AND LACE DOG HARNESS DRESS; $20

Pink Polka Dot and Lace Designer Dog Harness Dress
BaxterBoo

This feminine pink polka dot dress is simply adorable. It features a convenient built-in harness and comes with a matching leash.

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25. PET SWEATER VEST; $6

pet sweater vest
Amazon

Your dog or cat will look like an erudite Oxford professor in this sweater vest. Note that the button on the pocket is shaped like a bone.

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Animals
Switzerland Just Made It Illegal to Boil Live Lobsters
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No, lobsters don’t scream when you toss them into a pot of boiling water, but as far as the Swiss government is concerned, they can still feel pain. The path most lobsters take to the dinner plate is supposedly so inhumane that Switzerland has banned boiling lobsters alive unless they are stunned first, The Guardian reports.

The new law is based on assertions from animal rights advocates and some scientists that crustaceans like lobsters have complex nervous systems, making death by boiling incredibly painful. If chefs want to include lobster on their menus, they’re now required to knock them out before preparing them. Acceptable stunning methods under Swiss law include electric shock and the “mechanical destruction” of the lobster’s brain (i.e. stabbing it in the head).

The government has also outlawed the transportation of live lobsters on ice or in icy water. The animals should instead be kept in containers that are as close to their natural environment as possible until they’re ready for the pot.

Proponents of animal rights are happy with the decision, but others, including some scientists, are skeptical. The data still isn’t clear as to whether or not lobsters feel pain, at least in the way people think of it. Bob Bayer, head of the University of Maine’s Lobster Institute, told Mental Floss in 2014 that lobsters “sense their environment, but don’t have the intellectual hardware to process pain.”

If you live in a place where boiling lobsters is legal, but still have ethical concerns over eating them, try tossing your lobster in the freezer before giving it a hot water bath. Chilling it puts it to sleep and is less messy than butchering it while it’s still alive.

[h/t The Guardian]

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