Meeting the Ultimate Marine Survivor

The earliest horseshoe crab fossils are from the late Ordovician period (roughly 450 million years ago) and you will notice they have not changed much since – why should they when they have such uniqueness, their ability to survive exceeds that of most of their ocean friends.

So unique are they, that they have their own sub phylum, chelicerata and class, metrostomata. They are arthropods who are closely related to spiders, ticks and scorpions and look like the fusion of a crab, spider and a ray. Their hard carapace protects their soft underbellies and their long straight rigid tail is not used in defence but to right themselves if they accidentally flip over or as a rudder.

You guessed, they do not have gills like almost everyone else who lives in the ocean but have book gills shaped like the pages of a book for the exchange of respiratory gasses as well as movement through the water.

They are scavengers who feed mostly at night on worms and bivalves but can go a whole year without food and live for about 25 years. They have few natural predators because of their tough exoskeleton and are harvested for bait and fertilizer. At Sea World we feed ours pieces of prawn.
The females are bigger than the males and grow about 33% after each moult where the males only increase by approximately 25% each moult. They will mount 16 times until they are fully grown and reach sexual maturity at 11.

It is little wonder that this unique crab does not have haemoglobin in its blood like almost everyone else, but hemocyanin to carry oxygen. Because of the copper present in hemocyanin their blood is blue and is used extensively in the medical world. In India they have patented a method of bleeding the crabs and then returning them unharmed to the water. The compound Lysate is extracted from their blood and used in cancer research, as a diagnostic reagent to detect bacteria which cause diseases like meningitis and typhoid, an indicator of spinal meningitis as well as in a number of other diagnostic tests and production of insulin in diabetic patients.

These amazing creatures are amongst so many other fascinating animals living in the Aquarium at uShaka Sea World where the staff on hand are delighted to lead you on your journey of marine discovery.