Horseshoe crab blood (and, why conservation pays)


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    A mere 15 minutes from Manhattan, the horseshoe crabs are coming ashore.  

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    Good kitteh.

    They’re not really crabs though, they’re closer to spiders or scorpions.

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    As high tide approaches, more and more appear. They concentrate around the new and full moons in late May and early June.

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    Males clamp on to females using special clamp like pinchers.  

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    Sometimes as many as 14 males will climb on top of one female. 

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    They don’t pinch or sting; they’re very friendly! Look: This one gives free hugs!  

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    They’re actually...really...friendly. This one is trying to mate with a reporter’s boot.

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    Well, if you insist.

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    Volunteers tagging a crab.  They drill through the carapace which, apparently, doesn’t hurt them too bad.

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    Though if I were a crab, I’d probably be pretty mad about it. 

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    The tagged crabs are released back into the water. When people find the tagged crab, they can call a number to report it. It helps scientists study population movements and lifespan.

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    At a Charles River Endosafe facility in Charleston, South Carolina, live horseshoe crabs fill bins. The barnacles are removed, and they’re washed with a mild disinfectant. 

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    Told you they don’t sting! Their tails are used to help them flip over, and they contain photoreceptors to help them sense changes in light

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    They’re strapped into place. It looks kind of uncomfortable, but it’s also their natural defensive position.

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    Folding them up like this exposes their dorsal cardiac sinus, which is basically their little arthropod heart. 

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    It’s basically the matrix for crabs.  

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    Into the bubble they go.

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    People in scrubs -- except that one guy -– prepare the crabs for bleeding by swabbing their cardiac sinus membrane with alcohol.

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    Their blood is blue. It’s blue. Blue. Like Koolaid Blue. Whereas our blood uses iron-based hemoglobin as the oxygen carrier, the crabs use copper-based hemocyanin.

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    The crabs, drained of about 20% of their blood and still quite alive, are rolled out of the bleeding bubble and onto the next stop.

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    They are freed from their straps...

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    ...and headed back to the sea. Charles River Endosafe says 99.5 percent of its crabs survive the bleeding process, though some scientists suggest that across all biomedical harvests survival could be as low as 70 percent.

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    In All Atlantic States except New Jersey and South Carolina, the crabs can also be harvested as bait. This practice has been regulated since the late 90’s, as this graph shows.

    In 2012, 610,000 crabs were taken for bleeding and returned, of which the Atlantic States Marine Fishery assumes 85 percent survived. In contrast, 729,000 crabs were harvested for bait, of which none survived. The ASMFC says these levels, overall, are sustainable. But in certain regions like the Northeast, they are not. This graph does not include deaths from biomedical harvest.

    CORRECTION: An earlier caption misidentified the states where the crabs can be harvested as bait. The text has been corrected.


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    Complicating matters further, migratory shorebirds like the Red Knot depend on the Horseshoe Crab eggs for sustenance over the long migration. The Atlantic States Marine Fisheries Commission tries to include this in its models when determining acceptable catch rates for the bait fishery.

    - Wikimedia Commons

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    The final product of the bleeding operation is the Limulus Amebocyte Lysate test. It’s used to make sure medical equipment and supplies are safe for people to use – this means everything from IV’s to saline solutions to pacemakers to dialysis machines. It does this by detecting contamination by gram negative bacteria –- not simply determining if something is sterile, but if it even has traces of bacterial toxins that can cause fever or even septic shock. Here, the enzymes used in the test have clotted into a gel in the presence of trace amounts of bacterial toxins in tapwater.

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    Charles River’s advanced version is displayed here -- it’s a cartridge that’s fed into a portable digital reader, pictured in the background. It can detect bacterial toxins in parts per trillion.

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Quite possibly, the gentle horseshoe crab has swum ashore during the full and new moons of May and June to spawn for 445 million years. 

Horseshoe crab-like creatures were here when the dinosaurs appeared, and they were here after the dinosaurs disappeared. They survived ancient global warming and ice ages alike. And then people happened. 

“Over a hundred years ago, they were ground up and put on land as a fertilizer,” says Eric Hallerman, professor of fish conservation at Virginia Tech. In places like the Delaware Bay, 90 percent of the crab population was wiped out, and not a great many people cried about it. 

Then in the '70s, people discovered that they need the crabs for something much more valuable.  

“Every human on the face of the earth, if they’ve ever been given an injectable medicine, has been touched by LAL,” says Allen Bergenson with biomedical firm Lonza. 

LAL – Limulus Amebocyte Lysate  is a test for bacterial contamination made from the crab’s blood (usually made without killing the crabs). Lonza is one of four companies that manufacture it. The test is used throughout the medical industry to ensure medical instruments and materials don’t cause fever or complications when introduced to the blood.

It’s among the reasons that, gradually, people and governments started to care about the crab. 

“We’ve created laws that make sure the animals are returned to sea, that require them to be harvested by hand,” says John Dubczak, general manager with biomed company Charles River Endosafe in South Carolina. In that state the industry lobbied to ban fishermen from harvesting hundreds of thousands of crabs to use as bait for sea snails and eels. 

The Atlantic States Marine Fisheries Commission intervened in 1998 to relieve pressure on the crab from the bait industry. 

Now, the biomedical industry is competing within itself to see who can use the fewest crabs. 

Charles River has developed a highly sensitive test that only uses one twentieth the normal amount of horseshoe crab’s blood. Lonza has a synthetic version that doesn’t use any crab’s blood. The firms argue, sometimes bitterly, over which product is better. The synthetic version doesn’t have the same regulatory standing as the crab-based version (it’s not currently listed in the United States Pharmacopoeia, an official list of sanctioned drugs and uses), and for now that has dissuaded the pharmaceutical industry from embracing it.

Whatever the result, the competition raises a different way of thinking about nature.

“Instead of nature for nature’s sake, nature for people’s sake,” explains Janet Ranganathan, Vice President for Science and Research at the World Resources Institute. She’s referring to a concept called “Ecosystem Services.” When people realize the value in nature, and then pay to maintain it, everyone wins. 

In many cases, this approach has saved entire ecosystems.

“In the '80s, water quality was degrading in NYC because of development in the Catskill and Delaware watershed,” she says. Instead of building a $6 billion water filtration plant the city spent a fraction of that ($1.5 billion) just protecting the forests that purified water by paying landowners to maintain and restore it. 

It doesn’t always work, of course. Upstream agriculture on the Mississippi causes dead zones downstream that negatively affect fishermen, Ranganathan gives as an example. “You have one industry trumping another,” and polluters don’t have to pay for the disruption in services that nature provides. 

But things appear to be working out somewhat for the horseshoe crabs. Overall, the pressure on their population appears sustainable, according to the ASMFC, though there are troubling declines numbers in certain regions.

In some cases, making money off of nature can be a good way to protect it. 

About the author

Sabri Ben-Achour is a reporter for Marketplace, based in the New York City bureau. He covers Wall Street, finance, and anything New York and money related.

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