02 March 2024

Harvesting the blood of horseshoe crabs

One may wonder why the horseshoe crab is sensitive to endotoxin and, furthermore, how does the crab benefit from this phenomenon? As we know, seawater is a virtual "bacterial soup". Typical near-shore areas that form the prime habitat of the horseshoe crab can easily contain over one billion Gram-negative bacteria per milliliter of seawater. Thus, the horseshoe crab is constantly threatened with infection. Unlike mammals, including humans, the horseshoe crab lacks an immune system; it cannot develop antibodies to fight infection. However, the horseshoe crab does contain a number of compounds that will bind to and inactivate bacteria, fungi, and viruses. The components of LAL are part of this primitive "immune" system. The components in LAL, for example, not only bind and inactivate bacterial endotoxin, but the clot formed as a result of activation by endotoxin provides wound control by preventing bleeding and forming a physical barrier against additional bacterial entry and infection. It is one of the marvels of evolution that the horseshoe crab uses endotoxin as a signal for wound occurrence and as an extremely effective defense against infection.
Photo via Fresh Photons, but to read about this, I recommend the Horseshoecrab.org website.

Addendum:  A related story in the Washington Post in May 2012 reports at least an apparent temporary recovery in crab numbers.

Reposted from 2011 to add this update:
Conservationists fear that horseshoe crabs, a 450-million-year-old living fossil, will be pushed to the brink of extinction because of the value of their blood to the pharmaceutical industry. Horseshoe crab blood provides a natural source of limulus amebocyte lysate (LAL) which is used to test vaccines, drugs, and medical devices to ensure that they aren’t contaminated with dangerous bacterial toxins called endotoxins. With hundreds of thousands of horseshoe crabs captured and bled of their milky-blue blood each year, conservation groups are now stepping up their advocacy efforts and taking legal action to help save horseshoe crabs and the other species that rely on them.

Fortunately, there’s already an alternative to horseshoe crab blood: in the late 1990s, biologists at the University of Singapore created a synthetic version of the LAL called recombinant Factor C (rFC). Multiple studies show that rFC is just as effective as horseshoe crab-derived LAL, and it is currently commercially available...

In the Delaware Bay, home to the largest population in the US, horseshoe crab numbers have declined from 1.24 million in 1990 to less than 334,000 in 2002. Although the population appears to have stabilized, conservationists worry that increased demand for American horseshoe crab blood by the pharmaceutical industry could force it to go the way of the Asian horseshoe crab, Tachypleus tridentatus, which is rapidly disappearing in China and which the International Union for Conservation of Nature (IUCN) lists as endangered. Currently, the American horseshoe crab is listed as a vulnerable species.

The debate is particularly critical today; the COVID-19 pandemic has fueled a huge surge of research into vaccines and potential COVID-19 treatments which rely on the use of LAL to ensure product safety. As demand for vaccines and other medical products increases, conservationists worry that without a rapid switch to rFC, strain on the American horseshoe crab and the other creatures that rely on them will only get worse.
And I'll close with a repost of this killer Halloween costume:


Addendum 2024: A report in The Guardian about declining populations of horseshoe crabs, the spillover effect on migratory birds, and the availability of alternatives to horseshoe crab blood.

21 comments:

  1. Thanks for the read, I recently watched a great documentary about horseshoe crabs and they mentioned and showed how they harvested blood from them.

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  2. As I was reading the article, I had a sudden fantasy flash concerning UFO abduction experiences, in which humans play a role similar to the crabs when they're taken aboard the alien spaceships and subjected to what they describe as strange medical procedures. The aliens are actually siphoning off some substance from the humans that are useful in the alients' medical system.

    Just a fantasy, folks!

    --Swift Loris

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  3. The "Matrix" for crabs. I imagine there is a horseshoe crab "The One" somewhere in a computer fighting to freedom.

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  4. I went to take a bite of toast just as I read that title...lol

    Turned out to be much less gross than I thought, very interesting in fact.

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  5. Hi, this is absolutely grotesque, somewhere not far away an extraterrestrial is saying, "See I TOLD you they are barbarians, lets eat them!"

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    1. You sound foolish. Do you know how many lives are saved because of a simple blood donation from these crabs. Yeah it isn't voluntary on the crabs part but there is an over 90% survival rate. Also, when the crabs are brought in they are given a bath and barnacles that can weigh them down and hinder mobility are removed.

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  6. Neat-o (the blue color is super intriguing)
    I do find it interesting that in the picture, the tails have been removed, ostensibly in this case the crabs aren't expected to survive.
    I know that the picture is not connected directly to the linked website, which indicates that they make a point of only bleeding them 30% and once a year, trying to ensure that the crabs survive the process. I'd be curious where the differences lie in these practices. That being said, could the crab survive its tail being removed like that? Can it regenerate like other crustaceans?

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  7. I don't think that the tails have been removed... they are just bent under. You can see the tip of the tail on the first one, and searching google images of horseshoe crabs shows that the back portion of the crab does in fact bend that way.

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  8. Do the crabs survive this? Poor things...

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    1. Most do. I have great respect for the crabs.

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  9. that picture makes me sick, I really hate people.

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  10. what they fail to mention here is that yes, the crabs are released (relatively unscathed) back into the ocean. this pic is from a recent issue of national geographic, where they elaborate a little more on the process...

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  11. I perform the Endotoxin Assay as part of my job quite frequently and without the priceless donation from these wonderful crabs it would be impossible to do this test as effectively, if at all under regulated conditions. When I perform the Endotoxin test on the phase I experimental Muscular Dystrophy Gene Therapy Injectable that we make, the crabs and I are helping to ensure that these drugs Do No Harm when injected. Even low levels of Endotoxins can cause extreme inflammatory responses in people who are already sick, especially children.So think for a moment, either a very sick child or person can have a chance at finally becoming well and people in developed nations can have safety measures for health care items from eye drops to surgery, or we can ignore the valuable, renewable, and sustainable (if fragile) resource that is the horseshoe crab population and people can simply take a step back in medical development and lifespan. I also have great respect for the Horseshoe Crab and the contribution made, I'm beyond greatful. I ask that each person viewing the picture and reading the comments (commenting/having commented)just take a moment to find out the why behind any animal related research or scientific production you may hear about, investiators don't use animals fivolously this day and age, only when it is just so beneficial to humans or the animal species itself that one can't justify NOT performing the testing are animals used.

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  12. I completely understand why the crabs are bled. I've read up on it thanks to your blog initiating my interest. However, I am still disturbed by this picture. I find it really repulsive that we are bleeding these animals; albeit, we are saving lives.

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  13. Being unfamiliar with Gram-negative bacteria I looked it up, and reaffirmed my vow to never ever eat raw seafood.
    Thanks to these crabs donating to the blue blood bank where most survive, which is much better than the folks who chop them up for crab trap bait.

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  14. It's a horrific image. I understand the arguments justifying it, but they rely on the assumption (presumably held by the majority) that human welfare is superior to crab welfare.

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  15. We are invested in a Faustian relationship with nature. Of course there is a payoff in everything we do; that's why we do it. When we isolate one activity and look at the "good" it does, it's compelling. When we look at the sum-total of our collective actions, we see a dying biosphere. I tend to see the image of the crabs in light of the latter.

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  16. Seems like we'd better start using the alternative... your article says it's available so why aren't they using it?

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    1. Cost. The old go to on not doing the right thing.

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  17. If you ever visit the Delaware or Maryland seashore, you're going to see a ton of beached horseshoe crabs. Many of the ones lying on their backs are already dead, but some are still struggling. Be a kind soul and flip them carefully by lifting their shells from one side. Do not flip or pick them up by their tails.

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  18. I just think of moon bears.

    Seems Google has decided that information about testing on moon bears shouldn't be available ... least ways, I couldn't find any the first 9 pages.

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