Crab Blood is Gold

(Or why a living fossil may save your life)
According to the Ecological Research & Development Group (ERDG) of Delaware, whose primary focus is the conservation of the world’s four remaining horseshoe crab species, “an extract of the horseshoe crab's blood is used by the pharmaceutical and medical device industries to ensure that their products (e.g., intravenous drugs, vaccines, and medical devices) are free of bacterial contamination. No other test works as easily or reliably for this purpose.”

by Chris Brunson
Horseshoe crabs aren’t bugs. They aren't really crabs, either.

The prehistoric-looking creatures known properly as Limulus polyphemus are more closely related to spiders and scorpions than true crabs. The innocuous sea creatures are living fossils and have been scuttling about quietly pretty much unchanged for some 250 million years.

So who cares? As a primate who can think, you should. The primitive immune system of the horseshoe crab makes them medically quite useful to humans. Every drug certified by the FDA must be tested using the horseshoe crab derivative known as Limulus Amebocyte Lysate (LAL).

The LAL extract made from horseshoe crab blood (which is bright blue, by the way), is used to test drugs and vaccine for possible bacterial contamination.

Horseshoe crab blood is worth an estimated $15,000 a quart, according to the Mid-Atlantic Sea Grant Programs/National Oceanic and Atmospheric Administration Web site ( Researchers have also found substances in the crabs that have potential as antibiotics as well as anti-viral and anti-cancer agents. Try to put a price on that untapped potential.

Whenever you get a vaccine, the crab’s life is linked to yours as a benefit from medical testing. That’s very good, because bad bacteria can be lethal. Gram-negative bacteria can be nasty stuff that cause life-threatening diseases like meningitis, typhoid, cholera, and toxic shock syndrome.

Escherichia coli is benign in its proper environment; taken out of those rich corridors of gut and bowel, e.coli can cause serious illness.

Uncommon Story
Marine scientist William Sargent wrote a very readable book, Crab Wars: A Tale of Horseshoe Crabs, Bioterrorism and Human Health. One horseshoe crab can be bled, returned to the ocean, and after time, can give blood again. Or so it’s supposed to go.

Tapping the horseshoe crab market has spawned a multi-million dollar biomedical business.

Researchers are exploring the potential to culture cells that produce LAL. This development could potentially eliminate the need to catch the horseshoe crabs by the biomedical industry.

Keeping an eye on the health of populations are members of the Horseshoe Crab Technical Committee of the Atlantic States Marine Fisheries Commission (ASMFC), a commission created in 1942 in recognition that “fish do not adhere to political boundaries.”

The ASMFC is composed of 15 Atlantic coast states: Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida.

According to the Connecticut Department of Environmental Protection (DEP) the taking of horseshoe crabs by unlicensed persons is prohibited. “Only holders of the Connecticut Commercial Fishing License and Commercial Finfish License are permitted to take horseshoe crabs.”

In 2003 Congress allocated $630,000 for horseshoe crab research funding to Virginia Tech's Horseshoe Crab Research Center (HCRC) in Blacksburg, Virginia. Virginia Tech's HCRC is the largest horseshoe crab research institution in the country.

India and China are working on cloning toxin-detecting genes in horseshoe crab blood so that LAL derivatives could be made without the harvest of horseshoe crabs. United States biomedical companies include Associates of Cape Cod,; Cambrex,; and Charles River Endosafe,

Sea Life Goes On, Or Should
There are those who view the shelled creatures as bait or a nuisance; others see the lumbering critters as potential biters (they are harmless) and still others see the big picture. Horseshoe crabs are a natural wonder many take for granted. Not so for migratory shorebirds that depend on horseshoe crab eggs to help fuel their own journeys to breeding grounds.

"The crabs mate from late May to June from Long Island Sound along Connecticut and the north shore of Long Island. They are so innocuous,” said Catherine Ellis, curator, fish and invertebrates, Mystic Aquarium & Institute fore Exploration, Mystic, where the staff has raised horseshoe crabs from eggs. “When I grew up we thought the tail was a big stinging tool, and it’s not.”

The spiky tail is used by the crab to flip itself over when it’s washed upside down by waves or travel.

“They're ‘detritovores’ - that means that they sift through sediments for food. They really are totally harmless.”

According to, the Delaware Bay region is home to the “largest population of the American horseshoe crab (Limulus polyphemus), which is found along the western shores of the Atlantic Ocean from Maine to the Yucatan. Another three species live in the coastal waters from Japan to Indonesia.”

Regionally, nature centers offer canoe and kayak outings to view the mass migration of the shelled sea creatures in late spring/early summer, providing a tourism/recreation aspect to the horseshoe crab population. With life cycles tied to lunar cycles, the crabs come ashore to mate and return to the sea in many locations on the eastern Atlantic coast of the United States.

Inside Mystic Aquarium, the critters are on display for in-house education. Others travel with science educators for outreach programs within a 75-mile radius.

So are there enough horseshoe crabs out there to continue to inspire curiosity from beach-goers on the Atlantic coast as well as answer the need for biomedical purposes?

Money makes people do strange things.

Read Sargent’s book. Visit a touch tank with friends or family at an area aquarium to ask questions and see the crabs up close. (See listings under Resources, below.)

One last detail. Why the reference to a horseshoe for its name? Well, the animal was originally dubbed “horsefoot” due to its resemblance to a horse’s hoof.