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Mound House program focuses on horseshoe crabs

July 26, 2017
Jessica Salmond - News Editor ( , Fort Myers Beach Bulletin, Fort Myers Beach Observer

The horse shoe crab has lived through a lot. With fossil records of the strange sea creature dating 450 million years ago, this arthropod was in existence before dinosaurs. It watched them evolve and go extinct, saw the earth change and humans walk upright.

But, it's not even a crab. It's more closely related to spiders and scorpions, but unlike these cousins, it's completely harmless.

Mound House's Dexter Norris talked about this misnamed animal during his monthly Breakfast with a Biologist program Friday. Despite being a simplistic creature, it is a fascinating thing and vital to humans.

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The “shed” of a horseshoe crab is light in color and can be picked up along the beach.

"It's an unsung hero," he said.

Horseshoe crabs bleed blue from the levels of copper in their blood. They also have specialized blood cells called Limulus Amebocyte Lysate, which clot when they come in contact with bacteria toxins. For approximately 50 years, their blood has been used on a majority of medical procedures to test for contamination when administering vaccines and using surgical tools and medical devices.

It's become a $50 million a year industry, Norris said, and has also raised concerns for the health of the crab's survival.

Fact Box

Fun Facts from the Florida Wildlife Commission

Horseshoe crabs have 10 eyes, that mostly just detect light

Fossil records indicate these ancient creatures existed 450 million years ago, and have not changes significantly since.

They shed their outer skin and leave it behind

There are four species of horseshoe crabs that exist around the world, and only one, the American horseshoe crab, found in North America.

The blood is collected by medical supply companies. These companies collect the crabs, drain them of about 30 percent of their blood, and release them back into the ocean, Norris said, but little is known about the creature's survival rate after being released again. The stress of the procedure and the loss of blood could be weakening the population.

The horseshoe crab has been listed as a vulnerable species since 2012.

"We need to start worrying about our impact on them," Norris said.

Despite their hard shell and crunchy legs and tail, these animals are food for other predators like alligators. When they release eggs, birds will snack on them. They're even served up in some dishes.

There are no legal limits to how many crabs can be taken for blood use or for culinary purposes. The loss of natural habitat is also affecting them.

Norris said people are often misinformed about these animals, as they are intimidating and scary from the outside. But except for a few sharp spike-like ridges on their shell, horseshoe crabs don't have much in the way of defense. While their tails, called a telson, looks painful, the crab only uses it as a rudder in the water and to help right itself if it gets turned on its back on the beach. If threatened or attacked, its defense is to swim away, Norris said.

"No one's going to snuggle up to a horseshoe crab at night like a cat or dog," he said.



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