5 Fascinating Facts About Horseshoe Crabs 5 Fascinating Facts About Horseshoe Crabs

5 Fascinating Facts About Horseshoe Crabs

January 26, 2021


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Horseshoe crabs were sunbathing on the sandy beaches of New Jersey long before any shore-goers. Check out five interesting facts about these prehistoric invertebrates that have been on planet Earth since the Ordovician Period, which was 445 million years ago!

horseshoe crab horseshoe crab

1). Wait, what? It’s an Arthropod?

While a horseshoe crab is no spring chicken, it is also NOT a crab. These “living fossils” are in the invertebrate group, and are more closely related to spiders and scorpions. Horseshoe crabs have six pairs of legs, a hard shelled body with two large compound eyes and multiple smaller simple eyes atop the shell.

2). I always see them in the sand. Can they swim?

One would think the horseshoe crab’s six pairs of legs would suffice when getting around, but they also can swim. They swim to escape predators or to get around barriers they can’t climb. Horseshoe crabs are also known to swim upside down!
horshoe crab tail horshoe crab tail

3). Can it’s barb-like tail hurt me?

Even though their tails (also called telsons) may look dangerous, they actually use it to flip themselves when overturned. Horseshoe crabs are completely harmless to humans. Since they do not bite, and their claws have a weak grip, it is perfectly safe for you to roll up your sleeves and dip your hands in The Grotto touch exhibit the next time you’re at Adventure Aquarium.

4). Are horseshoe crabs only at the Jersey Shore?

While there are four species of horseshoe crabs, the Atlantic horseshoe crab is the only species that lives in the Western Hemisphere. Found mostly on the east coast as far north as Maine, and as far south as Florida, the Atlantic horseshoe crab likes sandy beaches. That means you won’t find these creatures on the west coast since those beaches are rocky and the surf is rougher than the Atlantic Ocean. The nice, sandy beaches of Ocean City and Wildwood allow horseshoe crabs to successfully dig holes to lay their eggs. You’ve also probably seen their leftover exoskeletons on the shoreline, that’s because a horseshoe crab molts about 18 times before they reach maturity.

5). Why are horseshoe crabs considered “Near Threatened” by the IUCN?

A horseshoe crab’s blood is the color blue, and contains limulus amebocyte lysate (LAL). LAL actually allows a horseshoe crab’s blood to clot when in the presence of bacteria. This attribute makes horseshoe crabs valuable to the pharmaceutical industry. In fact, horseshoe crab blood was key to making COVID-19 vaccines. Horseshoe crabs are also used as bait by conch and eel fisherman. Due to their high demand, there is actually a decline of horseshoe populations on the East Coast and in the Delaware Bay. 

Each summer, Adventure Aquarium partners with the Delaware Bay Horseshoe Crab Survey organization, other wildlife conservation groups and volunteers to take count of the horseshoe crabs on the beaches. This data helps gain insight to population status and trends ensuring their place and importance in our ecosystem. To learn more about Adventure Aquarium’s conservation efforts and how your membership supports conservation activities around the world and in our local community, please visit our Membership Matters page.

So, the next time you’re taking a stroll on the beach, and see a horseshoe crab stuck upside down, be sure to gently flip it over and let it go on its merry way! 


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