On a bright moonlit night, a team of scientists and volunteers head to a sheltered beach along Delaware Bay to study horseshoe crabs, which spawn by the millions along the US east coast from late spring to early summer.
The group walks up the shore, places a measuring frame on the sand, counts the people in it to create a population estimate, and recovers those unfortunate enough to have been thrown onto their backs by the tide.
With their helmet-like carapace, pointed tails, and five pairs of legs connected to their mouths, horseshoe crabs, or Limulidae, are not immediately endearing.
But if you’ve ever been vaccinated in your life, you have these strange sea creatures to thank: Their bright blue blood, which clots in the presence of harmful bacterial constituents called endotoxins, has been essential to testing the safety of biomedical products since the 1970s years ago when it replaced rabbit testing.
“They’re really easy to love once you understand them,” Laurel Sullivan, who works for the state government to educate the public about the invertebrates, tells AFP.
“They’re not threatening at all. They just go about their day trying to make more horseshoe crabs.”
For 450 million years, these otherworldly creatures have patrolled the planet’s oceans while dinosaurs appeared and died out and early fish transitioned to land animals that eventually gave birth to humans.
However, now the “living fossils” are listed as endangered in the Americas and vulnerable in Asia as a result of habitat loss and overexploitation for uses in food, bait and the pharmaceutical industry, which is on a major growth trajectory, particularly in in the wake of the Covid pandemic.
Recruiting citizen scientists helps engage the public while increasing government data-gathering efforts, explains the survey project’s environmental scientist, Taylor Beck.
– Vital Ecological Role-
“Crabs” is a bit of a misnomer for the animals, which are actually more closely related to spiders and scorpions, and consist of four subspecies: one that lives on the east and Gulf coasts of North America, and the other three in Southeast Asia.
Atlantic horseshoe crabs have 10 eyes and feed by crushing food such as worms and clams between their legs and then putting the food in their mouths.
The males are significantly smaller than the females, which they swarm out in groups of up to 15 animals when breeding. Males grab females when they go ashore, where the females lay golfball-sized clusters of 5,000 eggs for the males to spray their sperm on.
Millions of these eggs, tiny green balls, are accidentally blown onto the beach’s surface, where they are a vital food source for migratory shorebirds, including the near-threatened red knot.
Nivette Perez-Perez, community sciences manager at the Delaware Center for the Inland Bays, points out a giant ribbon of eggs that stretches almost the entire beach at the James Farm Ecological Preserve.
As she gestures, black-headed gulls swoop down to feast, aptly named black-headed gulls with bright orange beaks.
Like others in the area, Perez-Perez succumbed to the crab’s charm long ago.
“You’re so cute,” she says to a woman who has picked her up to point out her anatomical features.
– just turn them around –
Breeding is a dangerous business for horseshoe crabs, as they’re most vulnerable on the beach: when the tide comes in, some end up on their backs, and while their long hard tails can help some to fix themselves, not all are Happy.
Around 10 percent of the population is lost each year as their exposed undersides bake in the sun.
In 1998, Glenn Gauvry, founder of the Ecological Research & Development Group, helped launch the Just flip ’em campaign, encouraging the public to do their part by carefully picking up flipped crabs that were still alive.
“Where it matters most is the change of heart,” he tells AFP at Pickering Beach in Delaware Bay, proudly sporting a “Just flip ’em” baseball cap adorned with horseshoe crab pins.
“If we can’t get people to care and connect with these animals, they’re likely to want fewer laws to protect them.”
Each year, around 500,000 horseshoe crabs are harvested and bled for a chemical called Limulus amebocyte lysate, which is essential for testing against a species of bacteria that can contaminate medicines, needles and devices like hip prostheses.
The process’s mortality rate is estimated at 15 percent, with those who survive being released back into the sea.
A new synthetic alternative called recombinant factor C appears promising but faces regulatory challenges.
Horseshoe crabs are a “finite source with a potentially infinite demand, and these two things are mutually exclusive,” Allen Burgenson of the Swiss biotech company Lonza, which is running the new test, told AFP.
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