Beach Walks with Dr. Joe It’s Horseshoe Crab Time! By Dr. Joe Richardson When walking Tybee’s beach during this time of year, it’s not uncommon to see a live Horseshoe Crab washing around in the surf or partially buried in the wet sand. Now is when these animals move from offshore up onto the beach to pair-up and lay their eggs into the wet sand. We hear a lot about sea turtles using our nice sandy beaches for laying their eggs, but they do their beach activity at night, so we hardly ever get to observe it. But the Horseshoe Crabs are not as secretive, so your chance of getting to see them is much better. A Horseshoe Crab is not really a crab or crustacean, but rather, they are very old members of the Arachnid group of animals that includes spiders 26 TYBEE BEACHCOMBER | JUNE 2017 and scorpions. Like other Arachnids, they have a hard outer exoskeleton for protection. Although they look a bit scary, they really are harmless. The long pointed tail doesn’t have a stinger or sticker, and it is used mostly for turning itself back over if it gets knocked upside down. Those pinchers at the ends of the legs are not really strong, so they don’t have much of a pinch (nothing like a Blue Crab pinch). Its mouth is right there in the middle where all the legs come together. Offshore, Horseshoe Crabs burrow through the bottom searching for food like clams, snails and other smaller animals. If you really want to get into Horseshoe Crab trivia, you can tell if you have a male or female! Look at the legs. A female has pinchers on all the legs including the first pair, so that first pair looks like all the others. A male has pinchers on all the legs except for the first pair. His first pair of legs will end with a “hook” instead of pinchers. He uses those hooks to hold on to the female when they are laying eggs in the sand. I don’t know that much of anything eats Horseshoe Crabs because there really isn’t much meat inside them, and that hard exoskeleton provides a strong, effective protection. But they are actually harvested because they produce a very important biomedical product. Horseshoe Crab blood is blue, or at least bluish-purple, because it contains copper rather than iron like our blood. Once harvested, they are transported to a lab where some of their blood (or body fluid) is extracted with a syringe, and then they are transported back to the sea and released. Horseshoe Crab blood has a property that can detect certain impurities in our blood, so most all human blood products and artificial joints and other body parts are first screened with Horseshoe Crab blood extract to be sure they aren’t infected with foreign and dangerous micro-organisms. So during this time of the year, be on the watch for Horseshoe Crabs in the surf or on the beach. If they are partially buried in the sand, they will probably be okay til the tide comes back in. Dr. Joe Richardson is a retired marine science professor with 35+ years of research and teaching experience along GA and the southeastern coast and Bahamas. Besides research, he conducts Tybee Beach Ecology Trips year round (www.TybeeBeachEcology.com) and frequently posts pictures of what they are finding on his Tybee Beach Ecology Trips Facebook page.
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