Horshoe Crabs on the Troubling Decline

Horseshoe crabs are known as “living fossils” for they have been alive for 450 million years. These crabs predate the dinosaurs by more than 200 million years and have survived various ice ages, the breaking up of Pangea, asteroids, and periods of great extinction. These crabs are not true crabs (crustaceans) but are more closely related to spiders and scorpions. The pharmaceutical industry heavily relies on these crabs to ensure that their products are safe to use. Horseshoe crab’s milky blue (due to the presence of copper) blood is extremely sensitive to bacterial toxins (Endotoxins) present in any medicine, vaccine, injectable drug, or any medical device that enters the human body. The animal’s blood contains Limulus Amebocyte Lysate (LAL) which can detect bacterial contaminants such as endotoxins and clot around them, thus preventing the spread of the infection. If even a tiny amount of endotoxins enters the human body, the results can be deadly. The process of capturing the blood from the crabs is difficult and time-consuming, and as a result, a gallon of this blood retails for $60,000. 

This test, often called the LAL test works well and is much more efficient at detecting endotoxins than the method that was previously used. Before, pharmaceutical companies detected whether endotoxins were present in their medical devices by inserting them into rabbits and monitoring their temperatures. The first step of blood extraction from the crabs is to round up the crabs from the ocean floor and the beaches. The crabs are then taken to a site where about a third of their blood is removed (depends on various factors such as gender and maturity) and then the crabs are then returned to the ocean far from where they were collected, in order to prevent them from becoming re-bled. This crude process yields an estimated mortality rate of 30%. In addition, bleeding the crabs and returning them back to the ocean reduces that chance that they can mate, since crabs that were bled are slower and more lethargic. The crabs that survived are returned to the water, but no one is sure about if they recover or not. 

Unfortunately, the crab population is declining due to a coalition of factors including horseshoe crabs’ popularity as eel and whelk bait, a changing marine ecosystem, and the process of becoming bled. In 1990, an estimated 1.24 million crabs spawned in the bay, while in 2002, that number dropped to 333,500. The number in 2019 is around 335,211. A decreasing number of horseshoe crab eggs harms the ecosystem around, especially on the animals who rely on the eggs. Animals such as striped bass, flounder, diamondback terrapins, red knots, and ruddy turnstones are animals that are decreasing due to a lack of food such as horseshoe eggs. 

Thankfully a synthetic alternative does exist, called recombinant factor C (rFC) and some European companies have begun using it, but the American Pharmacopeia, which sets the standards for drugs in the U.S., does not believe the rFC is equal with horseshoe crab blood, claiming that its safety is still unproven.

Fortunately, some of the pharmaceutical companies that bleed the crabs are attempting to restore parts of the horseshoe population. One of these companies, named Cape Cod, reintroduced 100,000 juvenile crabs back into the ocean. Unfortunately, until rFC is approved or another synthetic alternative is found, the crabs will keep getting bled in these unhealthy conditions.


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