Horseshoe crabs, those alien-eyed walking helmets that scuttle in the shallows along New Jersey’s beaches, have quietly saved human lives for decades.

Now scientists have developed a manmade test that could take the burden off the lowly “king crab.”

Medical labs harvest a half-million of the hubcap-sized animals each spring to drain their blood, which is used to scan medicines and equipment for dangerous bacteria. If you have a pacemaker, if you are on dialysis, if you have ever had a flu shot or if you wear contact lenses, you have benefited from this incredible crab.

Farmers in southern New Jersey have fertilized their fields with them while commercial fishermen have cut them up for bait for conch and eel pots. But their medical uses touch millions of people all over the world every year — everything from intravenous drugs to battlefield dressings.

Blood harvest

Horseshoe crabs live along the East Coast from the Gulf Coast to Maine, but nowhere else on Earth can you find more horseshoe crabs than in the Delaware Bay each spring. The beaches of Cape May and Cumberland counties are covered with hundreds of thousands of crabs each May when they spawn under a full moon.

Medical labs take advantage of this phenomenon to collect crabs by the thousands to siphon their blood. Unlike human blood, red and rich in iron, the crab’s is blue and heavy with copper.

Horseshoe crabs evolved in the toxic brew of their ocean environment. When a crab is wounded, its blood coagulates and forms a barrier to keep out nasty bacteria. Unlike human blood, crab blood reacts the same way to all harmful microorganisms, making it the perfect agent to test the purity of drugs and medical implants, said Jordan Foster, vice president of the Wilmington, Mass., medical company Charles River Laboratories International.

“They’re primitive but able to live in waters teeming with millions of negative bacteria. ... If they get bitten or have a lesion, the wound clots to prevent infection,” Foster said.

Charles River is the biggest of four labs in the United States that manufacture a crab-blood product used in pharmaceutical testing. The company had $1.2 billion in net sales in 2009, according to the Securities and Exchange Commission. One of its biggest sellers is a portable scanner for hospitals and doctors’ offices that uses crab blood to detect bacteria.

Horseshoe crab blood is so sensitive, Charles River said, that it can detect the bacterial equivalent of one grain of sugar in an Olympic-sized swimming pool.

These tests are the most widespread medical use for horseshoe crabs. But researchers are finding new uses all the time. The U.S. military uses battlefield dressings made from the horseshoe crab’s chitinous shell to help stanch bullet wounds.

Bill Hall, a retired professor who has studied the crabs at the University of Delaware, said, “A hundred years ago, a few fishermen were using them for bait. Other than that, they were totally worthless. Now we have a whole biomedical industry that depends on their blood to test impurities.”

Useful even in space

The crabs are one of the most-studied animals on the planet. Three Nobel prizes were awarded to scientists for their work with the crabs.

“As far as marine invertebrates, they’re the most tested animal on Earth,” Hall said. “That covers a lot of territory. Simply put, this is an animal that watched the dinosaurs come and go. And it’s still here.”

Medical demand for horseshoe crabs has leveled off after years of steady increases.

Labs collected a record 512,552 crabs last year, according to federal numbers. An estimated 14 percent of them — and 300,885 since 2004 — died during or after bleeding, the commission said.

The crabs are taken to nearby labs. They are drained of their blood and returned within 24 hours to the same beaches or marshes where they were caught. Most are thought to survive the ordeal, but no long-term study has established that.

Meanwhile, more crabs destined for bait pots make a detour first through a lab, where their blood is drained, said Braddock Spear, spokesman for the Atlantic States Marine Fisheries Commission.

Astronauts use Charles River products to purify samples during experiments in space.

“Aboard the international space station, the circulation of air is poor. They’re conducting very sensitive microbial experiments where contamination could have adverse effects on the results,” he said.

The company gets most of its crabs from South Carolina, where there is no commercial fishery and the crab population is thriving, Foster said.

The company’s most popular product is a bacterial test that hospitals can administer in 15 minutes without sending samples to a separate lab.

In 2003, medical company Lonza Inc., located in Allendale, Bergen County, began selling a synthetic bacterial test that did not need the crabs.

“The main advantage I see is we do not have to bleed a horseshoe crab to manufacture it,” said Maribeth Janke, segment manager for endotoxin (bacteria toxins) testing. “It’s a sustainable resource. We would love to see usage of the horseshoe crab diminished as a result of the synthetic.”

While the product did not need U.S. Food and Drug Administration approval, companies do if they want to use it in place of horseshoe crabs. There’s the rub, said Thomas Novitsky, the former president of Associates of Cape Cod, one of the four labs that harvest horseshoe crabs. Now he serves on the Committee for the Conservation of Horseshoe Crabs, a nonprofit group that persuaded regulators in Massachusetts to limit this year’s crab harvest.

“It (the synthetic test) works better. It’s more consistent. But if you’re applying for this new use, you have to go through (expensive testing),” he said. “The FDA doesn’t care one iota about the horseshoe crab. What happens when there are no horseshoe crabs for anyone?” he said.

Contact Michael Miller:

609-272-7247