Horseshoe crabs, vital “living fossils” for vaccine safety

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 US east coast between late spring and early summer.

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

With their helmet-like shells, spike-like tails, and five pairs of legs connected to their mouths, these horseshoe crabs aren’t immediately endearing.

But these strange marine animals are vital to 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. been abandoned.

In addition to being harmless to humans, “they’re really easy to love, once you understand them,” Laurel Sullivan, who works for the state of Delaware tells AFP. these invertebrates.

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

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

– Vital Role-

The term “crab” is not entirely 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 South America North and in the Gulf of Mexico, and the other three in Southeast Asia.

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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 significantly smaller than females, which they gather in groups of up to 15 individuals when breeding.

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

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

Nivette Perez-Perez, a scientist with the Delaware Inland Bays Center, points to a large egg strip that stretches across nearly the entire beach of the James Farm Ecological Reserve, upon which black-headed gulls with bright orange beaks swoop down rush 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.

– Return them –

Mating is a dangerous activity for horseshoe crabs, as 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 up, not all are so lucky. About 10% of the population dies each year, their bellies baked by the sun.

In 1998, Glenn Gauvry, founder of the Group on Ecological Research and Development, took part in a campaign called “Just Turn Them Over”, encouraging the public to help 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.

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“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 explains.

Each year, approximately 500,000 horseshoe crabs are harvested for the pharmaceutical industry. Their blood serves 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 about 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 to be regulated.

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.

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