Horseshoe crabs, vital ‘living fossils’ for vaccine safety

On a moonlit night, scientists and volunteers stroll to a sheltered beach on Delaware Bay to watch horseshoe crabs, or “horseshoe crabs,” that spawn by the millions along the US east coast between late spring and early summer.

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The group goes to the shore and places a measuring frame on the sand to count the horseshoe crabs and straighten those that have been overturned by the tide.

With their helmet-like carapace, spiky tails, and five pairs of legs joined at the mouth, these horseshoe crabs aren’t immediately endearing.


Horseshoe crabs, vital 'living fossils' for vaccine safety

But these strange sea creatures are critical to vaccine safety: Their bright blue blood, which clots in the presence of harmful bacterial compounds called endotoxins, has been used more biomedically to test safety since the 1970s, when tests on rabbits were introduced products essential leave.

Aside from being harmless to humans, “they’re really easy to love once you understand them,” says Laurel Sullivan, who works for the state of Delaware, to AFP, telling the public about these invertebrates.

For 450 million years, these creatures from another age have roamed the planet’s oceans, witnessing the emergence and then extinction of dinosaurs and the transformation of first fish into land animals and then into humans.

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


Horseshoe crabs, vital 'living fossils' for vaccine safety

important role

The term “crab” is not entirely appropriate for these animals, which are more like spiders and scorpions, and are made up of four subspecies: one lives on the Atlantic coast of South America in the north and in the Gulf of Mexico, the other three in Southeast Asia.

Horseshoe crabs, also known as Moluccan crabs, have 10 eyes and feed by crushing their food, worms and clams, between their legs before bringing them to their mouths.

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

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

These eggs, tiny green balls, are also an important food source for migratory birds, including the near-threatened red knot.

Nivette Perez-Perez, a scientist at the Delaware Inland Bays Center, points to a large strip of eggs that stretches across most of the beach at the James Farm Ecological Preserve, on which bright orange-beaked black-headed gulls swoop down to feed.

Like others in the area, Mrs. Perez-Perez succumbed to the charm of horseshoe crabs. “You’re so cute,” she says to a woman, who picks her up to show off her anatomical features.


Horseshoe crabs, vital 'living fossils' for vaccine safety

give her back

Mating is a dangerous activity for horseshoe crabs, as they are most vulnerable on the beach: at high tide, some land on their backs, and while their long hard tail helps them stand up, not everyone is so lucky. About 10% of the population die each year, their bellies baked by the sun.

In 1998, Glenn Gauvry, founder of the Group on Ecological Research and Development, participated in a campaign called “Just Flip Them,” encouraging the public to help crabs that were still alive.

“Winning hearts is the most important thing,” he told AFP on Pickering Beach in Delaware Bay, wearing a cap with his slogan and adorned with horseshoe crab insignia.

“If we can’t get people to care about these animals and feel close to them, they’re probably going to want fewer laws to protect them,” he says.

About 500,000 horseshoe crabs are harvested for the pharmaceutical industry every year. Your 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.


Horseshoe crabs, vital 'living fossils' for vaccine safety

This process kills about 15% of horseshoe crabs, with the survivors being released back into the sea.

A new synthetic technique 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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