Meet the ultimate marine survivor – horseshoe crabs

  • 21 June 2012 | Lyn Britz

Guests reach out to touch a Horseshoe crab under the watchful eye of a member of the uShaka Sea World staff.

On your next uShaka Sea World visit make your way to the Treasure Chest in the Wreck Aquarium – there you will meet and perhaps even touch a living fossil – our Horseshoe crabs!!

Unchanged for over 250 million years - these unique animals are perfectly adapted to their life in the oceans. So unique are they, that they have their own sub phylum: Chelicerata and class: Metrostomata. They are arthropods and are closely related to spiders, ticks and scorpions. Their hard carapace protects their soft underbellies and their long straight tail is harmless and used to right themselves if they accidentally flip over and as a rudder to steer themselves in the water.

They are scavengers and feed mostly at night on worms and bivalve shells. They have few natural predators because of their tough exoskeleton. But people use them for bait and fertilizer. At uShaka Sea World we feed our horseshoe crabs on choice pieces of prawn.

Mature female crabs come ashore to lay their eggs in little hollows in the sand. Males fertilise the eggs, which are then left to develop, while the crabs return to the sea. During the next spring tide the little crabs are ready to hatch into tiny larval crabs, which are washed out to sea where they grow into adult crabs.

These unique animals do not have hemoglobin in their blood like other creatures, but they have hemocyanin to carry oxygen. Because of the copper in hemocyanin, their blood is blue. Scientists noticed that, when threatened with bacterial infection, the blue blood of the horseshoe crab clots. The clot surrounds the bacteria, protecting the rest of the animal from infection. The scientists realised that this could be used to make vaccines, injectable pharmaceuticals such as insulin and implantable medical devices that are free from toxic contamination. The LAL (Limulus Amebocyte Lysate) is extracted from the blue blood of the crabs and is used in medical procedures to detect incredibly small amounts of contaminants in medical equipment or intravenous solutions. The LAL test ensures the purity of insulin used by 175 million diabetes sufferers worldwide.

These amazing creatures are amongst the many other fascinating animals that live in the Wreck Aquarium at uShaka Sea World. Join us on a journey of marine discovery.

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