Close Encounters with the Horseshoe Crab

The underbelly.

The underbelly of a horseshoe crab. (Photo by C. Baute)

Whale sharks…crocodiles…sturgeons…ostriches…giant fern forests…the Redwoods: Some animals and plants immediately trigger in us a weird caveman-like sense that the Earth is millions of years old, one in which warmth and oxygen were plentiful and humans were non-existent.

For me, nothing triggers this feeling more than the horseshoe crab. God, they’re trippy. And old: 450 million years, with little that’s changed in their body structure.

Last week I got a deep dive in horseshoe crab biology thanks to Megan, a outreach director from the American Littoral Society, who took my coworkers and me on a tour at Sandy Hook Gateway National Recreation Area, in the far Northeastern corner of New Jersey.

As soon as we reached the beach, we all spotted a horseshoe crab in the sand, making its way back to the water. Megan immediately fell to her knees and began vigorously digging in the ground near the crab to see if it had laid eggs — it hadn’t.

Then, without hesitation, she picked up the creature and began a fascinating explanation of the life and times of the horseshoe crab….

They look like terrifying space aliens well-prepared to rip out your vital organs, but they're actually harmless.

Yes, they look like terrifying space aliens well-prepared to rip out your vital organs, but no. If that were true, we would have driven them into extinction a long time ago–our favorite solution for animals we’re even mildly threatened by. (Photo by C. Baute)

To begin with, we learned they’re gentle. Yes, with anything so primitive looking and resembling giant spiders wearing metal helmets, the natural response is to freak out a little when you first see one. But the guide told us they can’t harm people. Each of their feet/appendage-thingies can only lightly grasp a human finger, much like a newborn can hold a fellow human’s hand, but with even less strength than that. And their spiky formidable tails aren’t even a threat– they use their tails as a rudder, helping them get around, not as a defense mechanism.

Here I am demonstrating proper horseshoe-crab-holding-technique: by the sides of the shell, not the tail!

Here I am demonstrating proper horseshoe-crab-holding-technique: by the sides of the shell, not the tail!  Fishing waders optional, though they do enhance appearance of scientific prowess.  (Photo by C. Baute)

Also, they’re on the decline. That’s never shocking to hear, especially to my group, all of us environmentalists. Thankfully, Eastern seaboard states are increasingly limiting the harvest of horseshoe crabs, but it’s hard to know if that’s helping yet. One big hurdle to their continued survival is valuable blue blood, which is used in medical research, and the extraction process is gory.

A crustacean cornucopia.

A crustacean cornucopia. (Photo by J. Caswell)

Lastly we learned the females are bigger than the males. And they molt — up to a certain age, around 10, if I’m remembering correctly. Then they stop, and you can tell an old one from a young one based on the amount of sea life that’s hitched a ride on his or her shell. The one we encountered had a weird assortment of clams, conchs, barnacles and sea lettuce floating on her head, like if Carmen Miranda lived underwater.

After we all got a turn manhandling this one, we let her go, and she slowly meandered back to the water (they don’t move fast), and it was the most anti-climactic animal release I’ve ever been a part of. Seriously, it took her 15 minutes to scoot away, and many of us got bored and turned to the next activity: Launching a net to collect and record local species, mostly small fish, mollusks and hermit crabs. As part of this, I got to hold a tiny, tiny baby flounder.

Now this is cute.

Now this is cute. (Photo by C. Baute)

I wish I could do this every day (when the weather is nice).

Me, playing Ms. Marine Biologist in a giant, broken pair of men’s fishing waders. I wish I could do this every day (when the weather is nice). (Photo by J. Caswell)

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