Horseshoe crabs, vital “living fossils” for vaccine safety

< /p> UPDATE DAY

On a moonlit night, scientists and volunteers roam a protected beach in Delaware Bay to observe horseshoe crabs, or “horseshoe crabs,” which spawn in their millions along the east coast of the United States between late spring and early summer. 

The group walks to the shore setting a measuring frame on the sand to count horseshoe crabs, straightening those tipped over by the tide.

With their helmet-like shells, spike-like tails, and five pairs of legs connected to the mouth, these horseshoe crabs are not immediately endearing. 

But these strange marine animals are vital for vaccine safety: their bright blue blood, which clots in the presence of harmful bacterial compounds called endotoxins, has been essential for testing the safety of biomedical products since the 1970s, when tests on rabbits were introduced. abandoned. 

As well as being harmless to humans, “they're really easy to love, once you understand them,” Laurel Sullivan, who works for the State of Delaware to educate the public about these invertebrates. 

For 450 million years, these creatures from another age have roamed the planet's oceans, seeing dinosaurs appear and then die out and the first fish transform into land animals and then humans. 

< p>Today, however, these “living fossils” are listed as a vulnerable species in America and endangered in Asia, due to habitat reduction, overharvesting for food or bait, and use by the pharmaceutical industry, a major growth sector, especially since the Covid-19 pandemic.

Vital role

The term “crab” is not quite appropriate to designate these animals, which are more like spiders and scorpions, and are composed of four subspecies: one lives on the Atlantic coast of North America and the Gulf of Mexico, and the other three in Southeast Asia.

Horseshoe crabs, also called Moluccan crabs, have 10 eyes and feed by crushing their food, worms and clams, between their legs, before bringing it to their mouth. 

Males are much larger smaller than females, which they gather in groups of up to 15 individuals when breeding.

To reproduce, males spray their sperm on the golf ball-sized clusters , composed of 5,000 eggs, which they lay on the sand. 

These eggs, tiny green balls, are also a vital food source for migratory birds, including the Near Threatened Red Knot.

Nivette Perez-Perez, scientist at the Delaware Inland Bays Center , shows a vast strip of eggs stretching almost the entire beach of the James Farm Ecological Reserve, upon which black-headed gulls with bright orange beaks swoop in to feast. 

Like others in the region, Ms. Perez-Perez succumbed to the charm of horseshoe crabs. “You're so cute,” she says to a female she picks up to show off her anatomical features. 

The return

Mating is a dangerous activity for horseshoe crabs because it is on the beach that they are most vulnerable: with the tide, some end up on their backs, and although their long hard tails help them to stand up, not everyone is so lucky. About 10% of the population dies each year, their stomachs being baked by the sun. 

In 1998, Glenn Gauvry, founder of the Group on Ecological Research and Development, took part in a campaign called ” Just flip 'em,” encouraging the public to help the crabs that are still alive.

“Winning hearts is what matters most,” he told AFP on Pickering Beach in Delaware Bay, a cap bearing his slogan and adorned with horseshoe crab badges on the head.

“If we can’t get people to care about these animals and feel close to them, they’re less likely to want legislation to protect them,” he says. it.

Each year, approximately 500,000 horseshoe crabs are harvested for the pharmaceutical industry. Their blood is used in a chemical called Limulus Amebocyte Lysate, which identifies a type of bacteria that can contaminate drugs, needles, and devices like hip replacements.

This process causes approximately 15% of horseshoe crabs to die, with survivors being released back into the sea.

A new synthetic process, called recombinant factor C, shows promise, but has yet subject to regulation.

Horseshoe crabs are a “limited source with potentially infinite demand, and those two things are mutually exclusive,” says Allen Burgenson of Swiss biotech company Lonza, which makes the new test.