Horseshoe crabs have been utilized by the biomedical industry to save millions of lives around the globe for years. But now researchers fear the practice of bleeding them may be threatening their survival
Many medical laboratory scientists are aware that horseshoe crabs are harvested to get their blue blood and the limulus amebocyte lysate, or LAL (pronounce “el-ay-el”), because it can detect bacterial endotoxins. The popular wisdom has been that the collection procedure does not harm the crabs. However, there are growing concerns that indicate the biomedical industry is having a negative impact on the horseshoe crab population.
More than 600,000 horseshoe crabs are harvested annually for their blood in the United States (US). It is estimated that the blood is worth $60,000 per gallon and the global industry of processing the blue blood is valued at over $50-million per year, according to a CNN article.
The blood of the horseshoe crab is bright blue in color because it is rich in copper. Horseshoe crabs are bled in laboratories for a protein contained in their blood that scientists use to make LAL. This protein can detect bacterial endotoxins in clinical laboratory tests by solidifying when it comes in contact with certain bacteria.
LAL is prized by the biomedical industry because it can detect dangerous bacteria in injectable drugs, implantable medical devices, and on instruments and equipment. Federal law mandates that any medical device that is inserted or injected into a human body must pass the LAL test for contamination.
Capture, Bleeding, Leading to Depopulation of the Species
After the crabs are dredged from the ocean floor, or captured as they come ashore for breeding, they are transported to one of a handful of facilities authorized to perform the bleeding process. Once there, the horseshoe crabs are cleaned and sterilized, suspended upside down and inserted with a needle which extracts approximately one third of their blood. The helmet-shaped creatures are then returned to the sea.
Like all animals, horseshoe crabs have an immune system to protect them from infection due to an injury or presence of bacteria. The immune system of a horseshoe crab uses endotoxin as the major chemical signal that the crab is being infected. Even miniscule amounts of endotoxin will spark a clotting reaction. Types of cells in the blood called amebocytes are separated from all the harvested blood and broken open, or lysated, to release the coagulation properties. (Photo copyright: Popular Mechanics.)
An LAL solution is then concocted to test for endotoxins in medications and on medical supplies. After this solution is combined with a sample from a batch of medication or placed on a piece of equipment, the presence or absence of the clotting reaction signifies whether endotoxin is present or not. There are currently no other tests that can analyze the purity of medications with the same accuracy as the LAL test.
Fisherman Regulated but Not Biomedical Laboratories
The Atlantic States Marine Fisheries Commission (ASMFC) regulates how many horseshoe crabs fishermen can collect for use as bait. However, the biomedical industry is not bound to restrictions because the crabs are returned to the water after the blood is extracted. The number of crabs harvested by the US biomedical industry jumped 86% between 2003 and 2014, according to an article in Scientific American.
In “Changing Global Perspectives on Horseshoe Crab Biology, Conservation and Management”, Thomas Novitsky, PhD, Chief Executive Officer of Cape Cod Biosystems of East Falmouth, Mass., wrote, “Evidence is accumulating that mortality of bled horseshoe crabs is higher than originally thought [29% versus 15%]; that females may have an impaired ability to spawn following bleeding and release; and that bled crabs become disoriented and debilitated for various lengths of time following capture, handling, bleeding, and release.”
In 2012, a horseshoe crab subcommittee was created by the International Union for Conservation of Nature (IUCN), an organization that establishes global standards for species extinction. That subcommittee later determined the Atlantic horseshoe crab is “vulnerable to extinction,” which is just one level from its Red List of Threatened Species. Their report also stated that horseshoe crab populations could decrease by 30% over the next 40 years, the Scientific American article noted.
“I wouldn’t be surprised if they weren’t on the Red List very soon. The [Asian] populations are significantly declining,” stated John Dubczak, Director of Operations at LAL facility Charles River Laboratories in Charleston, S.C. “Between pollution, loss of habitat, and the animals being eaten in Asia, their populations are under a tremendous amount of stress.”
The facilities that perform the bleeding assert they are not harming the horseshoe crabs. Dubczak states his company has procedures in place to ensure the creatures will not be harmed during the bleeding process. They also provide economic incentives to their suppliers to help guarantee the crabs are being handled appropriately outside their facility.
“It reduces the injury, it reduces the stress, it’s better for [sustaining] the population, and it’s better for us,” Dubczak said in the Scientific American article, noting that the mortality rate for crabs used in his operation is just 4%. “One of my suppliers built a water slide to put the crabs back into the water. They love it!”
Christopher Chabot, PhD, Professor of Neurobiology, Physiology and Behavior at Plymouth State University in Plymouth, N.H. questions how the overall health of the crabs is affected by the 24- to 72-hours they spend out of the water during the bleeding process.
“As you might imagine, being an aquatic organism, that probably has an impact on their viability, their health, their mortality, perhaps, as well as their ability to bounce back after this bleeding,” said Chabot. It takes about a month for the horseshoe crabs to replenish the blood that was extracted and they are not very active after they are bled.
Horseshoe Crabs Critical to Marine Ecosystems
The biomedical industry isn’t the only threat to the survival of the horseshoe crab. Fishermen use them for bait to catch eel and conch. Many shorebirds, migratory birds, fish, and turtles dine on horseshoe crab eggs. In addition, developments along the shorelines are destroying their natural habitat and breeding grounds.
Since horseshoe crabs have a vital role in the preservation of marine ecosystems, it is crucial that alternatives to the current bleeding procedure are developed. Practical and cost-effective substitutes for the LAL test that do not require horseshoe crab blood are under development. A synthetic version of the clotting factor called recombinant factor C is made from cloned Deoxyribonucleic acid (DNA). A test called the monocyte activation test (MAT) uses human blood and may have the ability to detect endotoxin bacteria that horseshoe crab blood is unable to expose. At this time, however, the LAL test is the only one approved by the Food and Drug Administration.
These news reports about the shrinking population of horseshoe crabs along the Atlantic coast demonstrate how interconnected environmental issues are with society’s use of natural resources. Clinical laboratory managers and pathologists should take note of the fact that researchers determined that the number of horseshoe crabs harvested nearly doubled between 2003 and 2014. That raises the stakes for researchers to find a substitute for the limulus amebocyte lysate that is produced from the blood of horseshoe crabs and has some many essential uses in medicine and healthcare.
—JP Schlingman
Related Information:
Medical Labs May Be Killing Horseshoe Crabs
As Horseshoe Crab Populations Steadily Decrease, their Indispensable Medical Use is Threatened
