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Why do we harvest horseshoe crab blood? - Elizabeth Cox

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During the warmer months, especially at night during the full moon, horseshoe crabs emerge from the sea to spawn. Waiting for them are teams of lab workers, who capture the horseshoe crabs by the hundreds of thousands, take them to labs, harvest their cerulean blood, then return them to the sea. Why? Elizabeth Cox illuminates the incredible properties of horseshoe crab blood.


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TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Elizabeth Cox
  • Director Anton Bogaty
  • Animator Anton Bogaty
  • Associate Producer Jessica Ruby
  • Content Producer Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Narrator Addison Anderson
Additional Resources for you to Explore
Horseshoe crabs’ ancestors appeared over 450 million years ago, making them are one of the very oldest species on Earth. They’re not actually crabs at all--they predate true crabs by at least a hundred million years, and are more closely related to spiders and scorpions. The four extant species of horseshoe crabs probably diverged between fifty and twenty million years ago. We don’t know for sure how they’ve lasted so long, but, in addition to their special blood, their ability to tolerate a wide range of environmental conditions has probably helped them survive. Learn more about their anatomy here, and our impact on them here and here. 

Until Fred bang discovered LAL in 1956, the only test we had for bacterial endotoxin contamination was injecting thousands of rabbits. In spite of it’s negative impacts, the LAL test is a huge improvement over this method. You can learn more about Bang’s discovery here. Learn more about the Gram Stain, the most common test for bacteria contamination, here.

Customize this lesson

Create and share a new lesson based on this one.

About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Elizabeth Cox
  • Director Anton Bogaty
  • Animator Anton Bogaty
  • Associate Producer Jessica Ruby
  • Content Producer Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Narrator Addison Anderson

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