Horseshoe Crabs: The Medical Marvel of the Lowcountry

Hilton Head Island is known for many things including its beautiful beaches, active lifestyle, and amazing food. One thing that does not come to mind for most when dreaming of the island is the horseshoe crab. These armored living fossils can be found in the marsh and on the beach throughout the Lowcountry holding an essential role in our local ecosystem and the medical industry.


Fact #1 – Horseshoe Crab eggs and larvae are a top food source

With horseshoe crabs laying nearly 100,000 eggs a season it is no wonder so many animals rely on this major food source for survival. Top predators for the eggs and larvae are migratory shorebirdsred knot like the Red Knot and sea turtles. As horseshoe crabs become adults they continue to be preyed upon by sea turtles, sharks, and larger shorebirds. Don’t feel too bad for the horseshoe crab though, they eat clams, worms, and a variety of crustaceans as well as other smaller animals.


Fact #2 – The shell does not grow with them!

You may see a dead horseshoe crab on the beach but chances are its actually a molt of the exoskeleton. Like all insects and crustaceans, horseshoe crabs do not grow with their shell. Once they have outgrown their current shell they push through and grow a new one. This is called molting. Juvenile horseshoe crabs can molt upwards of twenty times before becoming an adult and never need to molt again.



Fact #3 – Horseshoe Crab blood is blue and is a Medical Marvel

Human blood contains hemoglobin to transport oxygen, horseshoe crabs use hemocyanin. The abundance of copper found in the hemocyanin causes the blood of horseshoe crabs to be a milky blue. horseshoecrab.jpg.653x0 q80 crop smartThis blood is incredibly sensitive to bacteria like e.coli and is used in the testing of vaccines. Horseshoe crabs are being farmed for their blood as a result of their medical and scientific properties, going for top dollar in testing facilities. For a full article on the process and ramifications we recommend reading this article after you have finished here!


Fact #4 – Horseshoe Crabs aren’t crabs at all!

These amazing creatures are not part of the crab family at all, they are Merostomata which means “legs attached to the mouth.” More appropriate cousins of the horseshoe crab would be spiders and scorpions.horseshoe crab116 Like spiders they have a pair of pincers near the mouth that is used to grab, hold, and push food toward their mouth. As night feeders they use these with their 6 other pairs of legs and 10 eyes to catch their prey and get a hearty meal in before sunrise.


Fact #5 – They are harmless

Did the spider thing scare you away! Come back! The horseshoe crab is harmless even with that spiked tail on its end. The tail serves the specific purpose of steering and correcting the body in the water and on land.images If they get flipped over they can often dig their tail into the sand and turn over. The spines along the sides of their body are sharp so caution is necessary if handling, but they are not out to harm you.




The Horseshoe Crab is vital to our ecosystem and a native to our area. Please respect these neat creatures next time you see one on the beach or in the marsh. If you come across one flipped over on its back take a second a turn them over to they can continue on with their journey – their survival and our ecosystem depends on you!


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