Horseshoe Crabs, COVID-19, and Climate Change: How Everything is Connected

4 min read
Horseshoe Crabs, COVID-19, and Climate Change: How Everything is Connected

One only has to take a cursory glance at the news cycle these days to see about a dozen and one stories about the development of COVID vaccines and their ongoing distribution. Rightfully so, as this unified global effort has yielded truly astonishing and unprecedented results, all thanks to the incredible contributions by medical workers and scientists alike.

However, there’s another little-known actor that has been quietly playing a critical role in processes like this for decades now: horseshoe crabs. It’s no understatement to claim that the entire field of biomedicine is beholden to these 450 million year old, ancient aquatic arachnids. Without them and their cerulean blue blood, there is no way any modern vaccine, IV, or implant could be developed and safely administered.

While it is relatively easy to “clean” injectables by purging them from any microbes (think of processes akin to pasteurization), the issue is that of endotoxins. These harmful components of bacteria can be released when they die, contaminating any sample they are found in, and they cannot be removed simply by killing the organisms. Prior to the 1970s, the only way to test for their presence in samples was by the costly and inefficient process of subjecting them to rabbits and monitoring their health for 3-4 days.

This is where horseshoe crab blood came in. Unlike humans, these creatures have an innate immune system, meaning that their blood contains antibodies which trigger rapid cascades of clotting upon detection of pathogens–including endotoxins. Capitalizing on this biological feature, scientists quickly developed the LAL (limulus amoebocyte lysate) test. By purifying the important clotting agents from the blood and adding a small amount of the solution to samples, the presence of endotoxins can be detected by clotting within 90 seconds. Not only that, but the LAL test is far away from the most sensitive screening we have, capable of detecting the presence of one part per trillion! So robust is this test that is now the global standard in medicine for screening things such as “intravenous drugs, clotting factors, insulin, vaccines, recombinant drugs and implantable medical devices (e.g., heart valves and orthopedic devices)”.

From this vampiric need has sprung an entire industry: horseshoe crabs are harvested from coastlines, drained of nearly a third of their blood and then released back into the wild. A gallon of this “blue gold” goes for upwards of 60,000$, making it the 4th most expensive liquid in the world. For years, scientists have been working on finding ways to synthetically produce LAL, but a reliable and industry-tested method is yet to be devised. Despite best efforts, we still need blood from wild horseshoe crabs.

Unsurprisingly, this has had huge ramifications on the horseshoe crab population over the years. While the LAL-industry claims only a 3% mortality rate of organisms upon release, recent studies show that it’s likely within the range of 10-30%, which accounts for the mortality of 20,000 to 37,500 horseshoe crabs per year.” Compounded on top of this is the ever-worsening ecological collapse of their natural habitat, from the likes of climate change and over-fishing. If nothing changes, one of Earth’s oldest living species, having already survived 5 mass extinctions, may very well go the way of the dodo bird.

Not only are we talking about the disappearance of a living fossil, but the disruption of entire ecosystems, as well as jeopardizing the continued existence of life-saving medical procedures.

This is far from a new story. Literal hundreds of species are going extinct everyday due entirely to human activity.

Cases like that of the horseshoe crab demonstrate that humanity does not exist apart from nature. Every being is connected on this planet in one way or another, and our current anthropocentric approach to life is untenable for all. It is only by taking care of the environment and preserving biodiversity that we can ensure a future on this planet for all beings, blue-blooded, or otherwise.

Works Cited

“Climate Change Affects Horseshoe Crab Numbers.” EurekAlert!, Accessed 13 Mar. 2021.

Donovan, Travis. “Scientist: Mass Extinction Happening Unlike Anything the World Has Seen since Dinosaurs Disappeared.” HuffPost Canada, 17 Aug. 2010, Accessed 13 Mar. 2021.

Drake, Nadia. “Horseshoe Crabs Are Spider Relatives, Genes Reveal.” Animals, 27 Feb. 2019, Accessed 13 Mar. 2021.

Krisfalusi-Gannon et al. “The Role of Horseshoe Crabs in the Biomedical Industry and Recent Trends Impacting Species Sustainability.” Frontiers in Marine Science, vol. 5, no. 2296-7745, 2018, 10.3389/fmars.2018.00185.

Madrigal, Alexis C. “The Blood Harvest.” The Atlantic, The Atlantic, 26 Feb. 2014,

Melvin, Alexi. “The 10 Most Expensive Liquids in the World.” Beyond Type 1, 19 May 2016,

Rafferty, John. “Horseshoe Crab: A Key Player in Ecology, Medicine, and More.” Encyclopedia Britannica,

“USP Provides Guidelines for Recombinant Factor c (RFC) a Non-Animal-Derived Reagent Critical to Development of Vaccines and Other Sterile Pharmaceutical Products.”,

Waycott, Bonnie. “Can Farming Horseshoe Crabs Help the COVID-19 Cause? «Global Aquaculture Advocate.” Global Aquaculture Alliance, 13 June 2020, Accessed 13 Mar. 2021.

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