Thursday, October 1, 2020

The Horseshoe Crab

Growing Up in Everglades City

Photo by Savannah Oglesby | Photo of the two Horseshoe Crabs mating at my Dock.

Have you ever wanted to witness a creature that lived during the times of dinosaurs? In the Everglades, within the Ten Thousand Islands, there is a creature that’s history is as interesting as its appearance. Horseshoe crabs are organisms that have existed on Earth for nearly 450 million years; far longer than dinosaurs. Hard to believe something could be so indestructible. If you look at fossils from the prehistoric era, their ancestors look almost identical to the ones living today. Although their name includes the word “crab,” they are more intently related to the arachnid side of the arthropod species, such as spiders and scorpions. Their name is based on their look, which resembles the shape of a horse’s shoe. Their class is Merostomata, which means that the mouth has the legs attached to it. Today, there are four living horseshoe crab species. The species in North America are called, Limulus Polyphemus, and are located on the Gulf coasts and alongside the Atlantic. The other three are located near Southeast Asia. 

Horseshoe crab’s outward appearance can be intimidating to some. Before I discovered they were harmless, if I saw one near the beach, I was afraid and would stay my distance. After I outgrew my fear of them, I learned to love, respect and appreciate them. As clumsy creatures, they can get flipped over on their backs by the waves easily. Their appearance consists of a hard exoskeleton; the front shell is called the prosoma and their shell on their back is called the opisthosoma. The telson is their long, pointy tail, and underneath their shells are ten legs. Something so incredibly interesting is that they have ten eyes. A pair of eyes are on the prosoma and the rest are located on other areas of its body, such as the tail, and are very sensitive. So, if you find one and want to pick it up, do not grab it by its tail, pick it up gently by both sides. This way you will not harm them. Horseshoe crabs feed at night on worms, crustaceans and mollusks on the ocean bottom, and they use their front legs to grab and lift food to its mouth.



Their blood is blue and helps to heal the wounds it receives by clotting. One of the reasons they were able to survive for this long is that they are able to live with small levels of oxygen. Looking back at the previous ages of marine deoxygenation, they were able to survive, unlike many other oceanic organisms. 

One memory I have with them is back in middle school when my friend and I were on one of the Ten Thousand Islands and discovered a cluster of baby Horseshoe crabs. They were so little and looked just like a miniature version of the adults, but more transparent. We picked up a few in our hands and dug a hole in the sand with water in it and placed them down. While my parents were sitting in their beach chairs watching the waves roll in, my friend and I were busy making little beds and other furniture for the babies out of sand and shells. We even named a few and thought of them as our own while we played. After a few hours of fun, it was time to leave, so we gently picked them up and placed them back where we found them. Just the other day before my dad and I jumped on our boat to head out fishing I saw two mating beside our dock. The male sits on top of the female while mating, as it hooks himself using his front claws. As they crawl from the shallow waters to the beach the male will fertilize the female’s eggs and eventually, she will lay them in her nest made in the sand. There are some instances of males not attaching themselves and still fertilizing the eggs. Females per season can lay more than 90,000 eggs, which is astonishing. Their mating season is year-round and usually nesting occurs during the full or new moon’s high tides. 

I find them mostly near the shores flipped over and unable to flip back because of the waves coming in. If they can’t flip back over, they eventually become dried out from the sun and die. So, if you happen to see one of these friendly arthropods flipped over on its back, do a prehistoric creature a favor and flip it over so it can return to the sea. 

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