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Today on Animal Fact Files we’re learning about horseshoe crabs. Don’t forget to subscribe to stay up to date on animal facts. All right, let’s just get this out of the way from the get go: horseshoe crabs are not crabs. They’re more closely related to arachnids like spiders and scorpions and they may be the closest living relatives to the trilobites. They’ve been around for millions of years and witnessed the rise and fall of the dinosaurs. And you might not know it, but you probably owe your life to these amazing animals.

Horseshoe crabs belong to the family Limulidae and there are four living species. They live in coastal waters in the Atlantic, Pacific, and Indian oceans and they come up on land to reproduce. Horseshoe crabs are really in tune with the moon which controls the tide. On late spring and early summer nights they will gather en masse on beaches when the moon is full (or new) and tides are at their highest. On the beach, lady horseshoe crabs will dig burrows and lay thousands of eggs within to be fertilized by males. It’s not uncommon to see more than one male clamoring for a female’s attentions, and a male will go so far as to hold on to the female and ride on her back to her nest. Freeloaders. Once finished, usually before the break of morning, all the adult horseshoe crabs will return to the water leaving their eggs defenseless.

The horseshoe crab babies that are able to survive the onslaught of predators that will then ensue will hatch a few weeks later. They’ll molt as they grow to become adult-sized which can be lengths of more than two feet (60.96cm) with females appearing larger than males. Horseshoe crab juveniles will molt approximately 16 times in the ten years before they reach adulthood. During their lifetime, horseshoe crabs enjoy meals of worms and molluscs such as clams as well as dead fish. They chew their food with their feet since they don’t have any teeth. Yeah, their feet. No joke. They’ll tear the food into small bits which can more easily fit into their mouths which are located between their legs. Horseshoe crabs can live to be more than 20 years old so long as they can avoid predators, which include humans.

As eggs and juveniles, horseshoe crabs are consumed in large quantities by shorebirds, crustaceans, and fish. As adults, horseshoe crabs face persecution from raccoons, foxes, sea turtles, alligators, and humans. Not only do people eat horseshoe crabs, but we also use them for their blood. Horseshoe crabs have a special clotting agent in their blood that is used to make LAL. LAL is a substance that is able to detect what are called gram-negative bacteria such as e. Coli. Since the 1970s, LAL has been used in the medical industry to assess for gram-negative bacteria which means it’s possible that horseshoe crabs have saved your life. Unfortunately, the only way to produce LAL is to harvest blue colored blood directly from horseshoe crabs. Horseshoe crabs are caught and brought to labs where approximately ⅓ of their blood is extracted at which point they are released back into the wild. It was once believed that this process was not detrimental to the individual horseshoe crabs being caught or to the general horseshoe crab populations, but recent research would suggest otherwise. At this point, we haven’t developed an alternative for LAL produced using horseshoe crab blood, so it’s a catch-22 of what to do - and for those of you thinking it, horseshoe crabs don’t live or reproduce very well in captivity. Atlantic horseshoe crabs have been classified as vulnerable with decreasing population trends, however, there are management plans in place to help alleviate some of the strain we place on horseshoe crab populations. Something you can do would be to simply raise awareness as most people are unaware of this information about horseshoe crabs.

It seems that people are generally afraid of horseshoe crabs because they look pretty dangerous, but they’re actually harmless to humans. Many people assume their tail (which is called the telson) is something akin to a stingray’s tail, but really it’s just there to help a horseshoe crab steer underwater and flip itself over if it ends up belly up. The spikes along the triangle section of their body aren’t used for spearing enemies but instead for gathering information about the surrounding environment including changes in temperature. They have many eyes, two of which are complex and stick out, looking like little horns, on their carapace (or their dome-shaped shell). Horseshoe crabs do have pinchers, to be fair, but, they’re not that big.They can also swim upside down, and they’re able to survive outside of water for much longer than your average fish. It just kind of goes to show there’s a reason horseshoe crabs have been around for such a long time!

For more facts on horseshoe crabs, check out the links in the description. Tell us your thoughts on horseshoe crabs in the comments. Give this video a thumbs up if you enjoyed it, and we’ll see you next time on Animal Fact Files.