Next time you spot the smooth helmet-like shell of a horseshoe crab by the beach, you might want to say “thank you.”
Horseshoe crabs ensure the safety of every vaccine, pacemaker and biomedical device in the United States. with their bacteria-detecting blood. While these living fossils, which have been around for 450 million years, save our lives, researchers are now asking what we can do to save them from the increasing needs of the biomedical industry.
Kepley BioSystems, Inc., a Greensboro-based life-science startup, published a review paper in June to explore the role and status of horseshoe crabs, which are also used as bait.
“We got a call one day from an eel and whelk fishery, and they explained that the growth of the biomedical industry and change in the coastlines had caused a collapse of horseshoe crabs, which made bait prices too expensive for them,” said Anthony Dellinger, president of Kepley, which had not previously dealt with horseshoe crabs. “I told some interns, ‘Look into this horseshoe crab thing, and tell me what you see.’
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“A week or so later, they came in, looked me dead in the eye, and said this is bigger than a bait problem. This is a species critical to the biomedical industry and society.”
Dellinger and his employees started thinking about how they could help the horseshoe crab.
“We want to re-evaluate the way we’re harvesting the blood from them and find new ways to manage the species more humanely and responsibly,” Dellinger said. “We need to be very thoughtful in dealing with them, as they’ve been thoughtful with making our lives more convenient and easier.”
A brief history of the horseshoe crab
Though we’ve been harvesting horseshoe crabs for fertilizer and livestock feed since the 1850s, they weren’t in trouble until the 1990s. Fishermen of eel and whelk, a kind of snail, use horseshoe crab meat as bait. We went from less than 20,000 pounds harvested per year in the 1970s to almost 6 million pounds in 1997.
Shorebirds rely on horseshoe crab eggs. The red knot, a rusty, robin-sized shorebird, flies from the bottom tip of South America to the Arctic Circle every spring, with a pit stop in Delaware, where the horseshoe crabs spawn. The birds gorge on millions of protein-rich horseshoe crab eggs to plump up before finishing their 9,300-mile journey.
Near the end of the ‘90s, conservationists noticed red knots were dwindling. They blamed decreased numbers of horseshoe crabs. The Atlantic States Marine Fisheries Commission stepped up, ordering a survey and banning fishing near the spawning grounds.
“Until the resource started crashing, nobody was willing to pay for the survey,” said Eric Hallerman, a professor and fellow of the American Fisheries Society, who has trawled the ocean every year since 2002 to estimate the horseshoe crab population. “The numbers started rebuilding as soon as we started restricting the fishery.”
By 2004, fishermen captured less than a million pounds of horseshoe crabs for bait. But by then, we had started harvesting horseshoe crabs for their life-saving blue blood.
What is LAL and how do we get it?
Horseshoe crab blood contains a special chemical, called LAL, which clots if it detects bacteria like such as E. coli.
Since the 1980s, researchers have used LAL tests on medical products. Before we knew about LAL, medical researchers did safety tests on rabbits by injecting them and watching them for fevers for three hours.
LAL tests, which are much faster and easier, replaced the rabbit test. Now, the pharmaceutical industry does over 70 million LAL tests each year.
A handful of companies in the U.S. bleed horseshoe crabs and extract LAL from the blood. One quart of horseshoe crab blood is reportedly worth $15,000.
Charles River Laboratories, in Charleston, S.C., is the closest company to Raleigh. In South Carolina, horseshoe crabs can only be collected for biomedical purposes, not bait.
Fishermen near Charleston collect horseshoe crabs by hand and deliver them to Charles River. Then scientists rig up the horseshoe crabs and puncture them near the heart to take 30 to 40 percent of their blood.
“[We] report the number of ‘unresponsive’ horseshoe crabs that we see during the course of each and every bleeding season,” John Dubczak of Charles River Laboratories wrote in an e-mail. “That number — which is a measure of stress incurred by all of the handling and transport — was less than 4 percent in 2017.”
The Atlantic fisheries commission estimates that 15 percent of horseshoe crabs die from the bleeding process. The problem, explained Hallerman, the professor, is that we can’t track the deep-sea creatures after they return to the ocean. One study demonstrated 29 percent mortality; another showed 3 percent.
“The 15 percent is an estimate of immediate mortality,” Hallerman said. “We simulated it in a study — captured them, took them somewhere else, bled them and held them in tanks. Only 3 to 5 percent of them died in two weeks. But it’s not the same as being released in the ocean.”
Does harvesting hurt the horseshoe crab?
Because we can’t track individuals after they return to the sea, we don’t know if taking their blood hurts the horseshoe crabs, said Dellinger, the scientist at Kepley BioSystems. Bled horseshoe crabs might not spawn as well as non-captured ones, or they might not spawn at all — no one knows.
“When you give a few pints of blood to the Red Cross, they give you a cookie and an orange juice,” Dellinger said. “Horseshoe crabs don’t have that luxury. It’s starting to have sublethal effects which contribute to their decline.”
Though biomedical companies used about 426,000 horseshoe crabs in 2016, the bait fisheries took far more with about 787,000 horseshoe crabs. Of those, up to 24 thousand come from North Carolina, where fishermen can net a maximum of 50 horseshoe crabs per day and ship them up north for bait to eel and whelk fishermen.
“The biomedical industry is the loudest advocate for the conservation of horseshoe crabs,” wrote Dubczak, of Charles River. “While the estimated mortality associated with our bleeding operations is approximately 15 percent, the mortality associated with the baiting for the eel and [whelk] fisheries is 100 percent.”
“The population decline in the Northeast is due to excessive baiting. In stark contrast, the population in the Southeast is increasing.”
The future of the industry
Dellinger wants the industry to do better. He dreams of ending the capture of wild horseshoe crabs. Aquaculture, or farming of fish like tilapia and catfish, is a $25 million industry in North Carolina. So Dellinger is working on new methods for farmers to aquaculture and bleed their own “free-range” horseshoe crabs, which can live for two decades.
“One day, growers could grow horseshoe crabs on site, and they’d have a recurring source of revenue,” Dellinger said. “If it’s done correctly it doesn’t come at the demise of the horseshoe crab, and it can create economic value for 10 to 20 years for the farmer. We would train and teach these growers how to maintain them.”
Expanding on his vision, Dellinger said that we could end our dependence on wild horseshoe crabs even if individual farmers aren’t on board.
“We could have dedicated estuaries, like environmental protected zones, where we could track, control and maintain them and have access to their raw materials,” Dellinger said.
If Dellinger and Kepley BioSystems solve the puzzle of maintaining horseshoe crabs in saltwater ponds, they could change the industry by benefiting both small farmers and wild horseshoe crab populations. Or they could join the other LAL producers in the $50 million industry.
“A lot comes down to what they can accomplish and if they can produce LAL inexpensively,” said Hallerman, the professor. “At some point some bright people will have a system that works. Then the question will be, what’s the attitude of the people who solve this? Will they put the LAL out there cheaply and revolutionize this, or will they make a ton of money until someone else cracks it?”
Other companies are creating synthetic replacements for LAL, which needs to be approved by the Food and Drug Administration before biomedical companies could use it to test their devices. The main LAL companies, including Charles River Laboratories, might be working on more efficient ways to extract LAL from the blood, so they would use fewer horseshoe crabs and make more of their product.
Horseshoe crabs have been around for a long time, and Dellinger wants to make sure they stay that way.
“We’ve only been using these animals in this way for 20 years,” Dellinger said. “We’ve only dealt with one lifetime of a horseshoe crab, and we’ve done significant damage to a species that has survived some of the most catastrophic events on this planet. In order for things to recover, it’s going to take time.”
“There’s a tipping point on this pendulum that could have already been tipped. It’s come time that we revolutionize the way we bleed horseshoe crabs. It will change the way the industry has been doing things, and it will make it a little more difficult, but I believe it will result in better and more [LAL compounds] and healthier horseshoe crabs overall.”