THE HORSESHOE CRAB

Wednesday is science day for this blog site, and today I reach into my bag of odd creatures and select the horseshoe crab.  The odds are high that you have never seen one.

• 
  There is an Atlantic species that lives along the coastline from Maine to the Yucatan Peninsula.
• There are three other species, mostly found in Southeast Asia.
• Coastal areas having none of them:  Europe, Africa, South America and large parts of Asia and the Pacific.

• 
  Aquariums generally don't have them.  These are Kujukushima horseshoe crabs at the Saikai National Park in Japan on Kyushu near Sasebo.
• They spend most of their lives in deep, offshore waters, only coming to shallow coastal beaches to spawn during high tides at night during full and new moons.
• There has been habitat destruction.

Another reason is that, where they are found, large-scale and unregulated operations have killed them off.

• From the 1850s to the 1960s, millions of horseshoe crabs were annually harvest primarily for use as fertilizer and livestock feed.  Demand declined as alternative fertilizers became available.
• In the 1990s, they were used as bait for the American eel and whelk fisheries.  Populations declined so some areas banned their harvest.

A new demand came when the biomedical industry began to use horseshoe crab blood to produce Limulus amebocyte lysate (LAL), useful for testing vaccines, medical devices and injectable drugs for bacterial contamination.

• Became controversial because this is a "catch-and-bleed-and release" process, which causes mortality and ruins their health.

• 
  Nearly a million of them were harvested in 2022 alone.
• And yes, their blood is blue-colored due to a copper-based protein called hemocyanin.
• Normally clear in the crab, but turns blue when oxygenated.
• Horseshoe crab blood costs $60,000 per gallon.

• 
  The Delaware Bay region has banned the harvesting of female crabs.
• Environmental pressures have shifted towards synthetic alternatives.
• Recombinant Factor  (rFC).
• recombinant Cascade Regent (rCR).

Well, that's a lot of detail for what itself is a mysterious creature.  The Horseshoe Crab:

• Are arthropods of the family Limulidae.
• Yet, they are not true crabs, or even  crustaceans.  

• 
  They are chelicerates, more closely related to arachnids like spiders and scorpions.
• Gets its name from its horseshoe shape.
• Has changed little since they first appeared in the Triassic Period around 250 million years ago.  
• It is a living fossil.

• 
  Eats worms and mollusks living on the ocean floor, usually at night.
• While having little meat, still viewed as a delicacy in some parts of Southeast Asia, and must be properly prepared to prevent food poisoning.
• The mangrove horseshoe crab contains tetrodotoxin and cannot be eaten.

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