Horseshoe crabs have a vital role in the development of a coronavirus vaccine. Here’s why – USA TODAY

The horseshoe crab, with its blue blood and helmet-like shell, is like a real-life dinosaur. Their blood is widely used for research. Fort Myers News-Press

The horseshoe crab's fluorescent blue blood is its best line of defense against toxins. For 40 years, humans have harnessed that same power to help keep us safe.

GREENVILLE, S.C. Allen Burgenson had a job, his father explained as they stood on the sand.

This was Allen's first fishing trip, but he wasn't going to take anything from the bay. Hewas to return the water's gifts to the deep, where they'd belonged for hundreds of millions of years.

If he spotted a horseshoe crab on its back, his father said as he held Allen's hand, that meant it was in trouble and needed Allen's help to get home. Allen just had to flip it over. Its10legs could make it the rest of the way back to the crashing waves.

Allen did just that on that day in 1963 in Sandy Hook, New Jersey, when he was 3years old. That's what he still does today. Whenever Burgenson enjoys a stroll along the East Coast, he is still a lookout for the stranded sea creature that's unlike anything else on the planet.

In 1963, Burgensondidn't know that inside each of those ancient animals he saved was something that would help save millions of us during his lifetime.

In 2020, the horseshoe crab is poised to assume a vital role in a drug the whole world awaits, a COVID-19 vaccine.

Without masks and a vaccine, we could reach Herd Immunity from COVID-19, but deaths would skyrocket. We break down the science of it. USA TODAY

Around the same time Burgenson was a boy on a beach,Jack Levin and Frederik Bang collaborated on horseshoe crab blood experiments. Their work led to a process that channels the almost magical force of the horseshoe crab's immune system, one that's helped the animal survive longer than most of the species that ever roamed the Earth or scurried across the ocean floor.

Since the late 1970s,horseshoe crab blood has been approved to make what's called the Limulus amebocyte lysate test, or the LAL test an alarm system triggered by a type ofbacteria that can cause fever, and in some cases,death.

It works like this: A mixtureof lysate is made from the horseshoe crab's amebocyte or blood cells. That fluid is added to whatever material a researcher is testing for safety. Depending on the test, the fluid willeither clot or change color to signal the presence of a dangerous toxin.

John Dubczak, an executive director with Charles RiverLaboratories, one of the companies licensed by the U.S. Food and Drug Administration to produce the LAL test, said it"has unequivocally elevated the quality and safety of injectable pharmaceutical drugs and medical devices, and that includes all of vaccines that protect us."

The crab usually no bigger than about 19 inches across, has a significance that outsizes its foot or claw print.The Limulus polyphemus, or Atlantic horseshoe crab, lives only up and down the East Coast and a small part of Central America. Less than half a million horseshoe crabs were brought to biomedical facilities in 2018, according to the most recently published data from the Atlantic States Marine Fisheries Commission.

"The world's health care can thank the horseshoe crab," Burgenson said.

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On Sept. 16, Robert Redfield, director of the Centers for Disease Control and Prevention, told a Senate panel that a vaccine might not be ready until next year. On thesame day he testified, the novel coronavirus cases totaled about 30 million globally, and there were about 942,000 associated deaths.

No matter what vaccine in trial wins the race to market, LAL will be the standard to test the safety of any materials that go into the medication, as well as the final product itself. All of that LAL will come from four production facilities in South Carolina, Massachusetts, Maryland and Virginia.

The demand of 5 billion COVID-19 vaccine doses won't be a burden, said Burgenson, chair of the Horseshoe Crabs Advisory Panel to the Atlantic States Marine Fisheries Commission. He estimated that at most,the facilities would need about three days of normal production to provide the material needed to test the vaccine's safety, and one of those days of productionto test the vaccine itself.

This gift will be given by an animal that's been long misunderstood and maligned, said Burgenson, a microbiologist with almost 40 years of experience in the pharmaceutical industry.

The horseshoe crab has long been overlooked and overfished. Humans are the biggest threat to theinvertebrate whose ancestry traces to the age before the dinosaurs, more than400 millionyears before humans walked the Earth.

And when we did finally meet them, we didn'teven get the thing's name right. Turns out, the horseshoe crab is not even a crab.

Tampa officials closed Ben T. Davis beach in July 2008 after dead fish and horseshoe crabs washed up on shore.(Photo: Chris O'Meara, AP)

Horseshoe crabs are more closely related to the spider than the crab, saidDaniel Sasson, assistant marine scientist at South Carolina's Department of Natural Resources. Like the spider, it has a lot of legs and eyes and pincer claws they use to feed.

That's not to say they don't have anything in common with the crab. Like a crustacean, theyshed an exoskeleton as they grow. You might have seen one washed ashore, especially after a storm.

It's got something that looks like a tail called atelson used to flip over the body, which can weigh 10 pounds. It's not poisonous. It's not a weapon, even though it looks scary enough to show up in a sci-fi scene.

All these attributes add up to one rugged, hardened tank-looking thing.Asteroids and volcanoes haven't even been able to take them out.

The blue blood is its best line of defense. Cells essentially builda fortress in seconds.

Amoebocytes, a type of blood cell, can "detect any outside particle," Sasson said, and once they do, they spring into action, whether the enemy invader is in the bloodstream or a wound outside of the body.

"How quickly the blood coagulated around the wound was amazing," he said. "Say you break off a piece of a claw. You'd see a little bit of blood for, you know, 10,15 seconds. And then it would stop because it would already have coagulated completely where the wound was."

Each year, the horseshoe crab crawls to the beaches to reproduce, and this ritual provides a rich and unusual opportunity for up-close study on beaches from Mexico to Florida, Georgia to Maine.

The peak is typically during evening high tides under a full or new moon. Females will lay about 4,000 greenish eggs, each about the size of the head of a pin. She might lay several clusters over the course of the season, up to 100,000 in all.

Some males arrive on land attached to the female's back. Others join them to compete to mate. They will huddle together, often in clusters of five or six. In Delaware Bay, the clusters are big enough to call galaxies.

Sasson saw the spectacle once. He heard it first.

"You could hear the clacking of their shells from, you know, way before you got to the beach," he said. Hundreds of thousands will swarm the beaches, he said. A dozen to 20 might pile up on top of each other within a few feet.

Horseshoe crabs, which mate year-round but more frequently in March and April, hook up in April 2019 on the south side of the Titusville Causeway east of the Max Brewer Bridge in Florida. Citizen scientists Laurilee Thompson and Bill Klein counted 5,000 crabs.(Photo: MALCOLM DENEMARK/FLORIDA TODAY)

South Carolina has some of the strictest and earliest horseshoe crab protections in the country. Since the early 1990s, state law prohibits anyone from even holding a horseshoe crab without a permit.

The horseshoe crab populationhas been stable or growing for many years. The state keeps count, doing a random survey by trawling annually.

Other regions don't fare as well. New York's stock assessment is poor. Factors that contribute to marine animal population decline range from pollution to loss of coastal habitat from development or the rising seas.

Concern for the horseshoe crab's future spiked in the late 1990s. The red knot shorebird population was declining, signaling trouble on the horseshoe crab front. The migratory birds relyon the horseshoe crab eggs for fuel to fly about 20,000 miles each year.

In Delaware Bay, as many as a million of thebirds will stop to gorge themselves during spawning, often doubling their weight.

Subsequent regulations and other protections have helped both the red knot and horseshoe crab numbers bounce back. That's not been the case on the other side of the globe.

The Atlantic horseshoe crab's Asian cousins have been decimated in some places, Burgenson said.They do not enjoy the same legal protections. In Asia, the horseshoe crab is used for medical purposes, bait and food.

When it comes to the conservation effort, the horseshoe crab does have a bit of an image problem. All the things that make it a survivor the hard covering, the spiky tail, the bright, blue blood make it not cute and cuddly.

Burgenson does what he can to change people's perspective. He even gave his grand-niece a plush toy version of the horseshoe crab for her crib collection.

He leads educationallectures as the chair of the horseshoe advisory panel. This month,he's doing a Zoom talk about the role of the horseshoe crab in the COVID-19 vaccine.

And he still flips upside-down horseshoe crabs when he sees them.

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Horseshoe crabs have a vital role in the development of a coronavirus vaccine. Here's why - USA TODAY