Horseshoe crab blood is a vital resource to the medical field. It's unique in more ways than one: the blue color and its ability to identify bacterial contamination in small quantities. Horseshoe crab blood contains a special amebocyte that is separated and then used in FDA testing. There's a lot of questions as to how blood harvesting affects the American horseshoe crab population, but some researchers are dedicated to the cause of protecting such a significant resource.

When asked to comment Charles River Labs responded with the following: "Charles River is dedicated to the protection and conservation of HSCs and has been an advocate for the humane treatment of horseshoe crabs for more than 25 years. In 1992, we worked with the SC-DNR to enact state legislation that called for the management and regulation of horseshoe crab fisheries, prohibiting the use of horseshoe crabs for bait. Due to these regulations, the horseshoe crab population in South Carolina is increasing and has been for the past 15 years. Understanding the vital role HSC’s unique blue blood plays in the safe discovery of new medicines and therapies, we are proud to be an industry leader in horseshoe crab conservation efforts." Following is a transcript of the video.

Narrator: This blueish liquid is one of the most expensive resources in the world. No, it's not the blue milk from "Star Wars." It's actually blood from a horseshoe crab, and the stuff this blood makes costs $60,000 a gallon. So why is it so expensive and who's buying horseshoe crab blood?

The blue color comes from copper in the blood. But that's not its most interesting feature. The blood contains a special clotting agent. It's used to make a concoction called Limulus amebocyte lysate or LAL. Before LAL, scientists had no easy way of knowing whether a vaccine or medical tool was contaminated with bacteria. Like E. coli or salmonella. Scientists would inject vaccines into huge numbers of rabbits and then basically wait for symptoms to show up. But when LAL was approved for use in 1970, it changed everything. Drop a minuscule amount of it onto a medical device or vaccine, and the LAL will encase any gram-negative bacteria in a jelly cocoon. While it can't kill the bacteria, the jelly seal is like a fire alarm. Alerting us to the presence of what could become a potentially lethal infection and prevent it from spreading.

Each year, the medical industry catches around 600,000 horseshoe crabs. The crabs are drained of 30% of their blood and up to 30% of the crabs don't live through the process. The survivors are returned to the water, but no one really knows how well or if they recover. In 2016, the International Union for the Conservation of Nature bumped the American horseshoe crab up to vulnerable on it's red list, one step below endangered. And the US population could keep falling, by as much as 30% over the next 40 years.

LAL Labs claim that the returned crabs eventually recover, but new evidence suggests that's not always the case. Win Watson is trying to figure out what happens to the crabs when they're put back in the sea.

Win Watson: So, the most immediate negative effect is mortality. Anywhere from 10% to 25% of the animals will die within the first couple days after bleeding.

Narrator: Bled crabs become disoriented and weak for a period of time, and females may have trouble spawning.

Watson: If they survive the first – I'll say two weeks, week, two week — and they're back in their natural habitat they did pretty well.

Narrator: But it's getting through those two weeks that's the issue.

Watson: You know, based on our data and other's I think that you need to treat them a little — if you're going to get — increase their survival rate, right, you need to treat them better.

Narrator: Scientists are trying to find a synthetic alternative to help reduce the strain on the horseshoe crab population. But so far, LAL is still required by the FDA for this type of testing. So if these animals really aren't recovering at the rate companies previously thought, we might eventually run out of crabs to bleed. If that happens, our lives and the lives of countless rabbits, might be at risk.