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"Horseshoe crabs are facing a threat due to excessive harvesting, resulting in a significant decline in their population."
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“Horseshoe crabs are facing a threat due to excessive harvesting, resulting in a significant decline in their population.”


These are stunning photographs being exhibited at the Wildlife Photographer of the Year show in London. Breathtaking images featuring peculiar creatures with shining shells and numerous legs moving swiftly along the ocean floor are now showcased on the walls of the Natural History Museum in the city.

Laurent Ballesta’s prize-winning pictures resemble creatures from other planets, but in reality, they are horseshoe crabs. These ancient species have existed for millions of years and are among the oldest known on our planet. Found on the ocean floor, they feed on worms, algae, and clams by crushing them with their legs.

Although horseshoe crabs and humans are not closely related, they play a crucial role in modern society. The reason being, the blue blood of these peculiar creatures is essential for testing the safety of various medical treatments, including vaccines and insulin injections, that are widely used by humans now.

According to Rich Gorman from Sussex University, harvesting horseshoe crabs for their blood has played a crucial role in saving countless lives. Thanks to their contribution, vaccines have been made safer and more effective.

According to Gorman, the use of horseshoe crabs, which are actually more similar to spiders than crabs, comes with a cost. Researchers warn that the species is facing significant evolutionary threats and their population has been rapidly declining, especially in the eastern coast of the United States. Large numbers of these crabs are being harvested for their blood, resulting in numerous deaths and decreasing numbers in vital breeding grounds like Delaware Bay in New Jersey.

The horseshoe’s decline has had a larger impact on the environment, leading to a significant decrease in bird populations, including the rufa red knot.

During the spring season, numerous red knots would migrate from the southernmost point of South America to Delaware Bay. There, they would consume the abundant eggs laid by crabs during the spawning period. These birds would then continue their migration of 9,000 miles to the Arctic. Yet, there has been a noticeable decrease in the population of red knots, attributed to the dwindling numbers of horseshoe crabs.

Furthermore, horseshoes serve as a crucial bait source for fishermen, and their rampant use has further added stress on the ecological balance of the horseshoe. Consequently, a restriction was enforced this year prohibiting the collection of female horseshoes in Delaware Bay.

Many ecologists argue that there is no justification for the continued use of horseshoe crabs as bait or for medical purposes. According to Larry Niles, a wildlife biologist from New Jersey, fishing industries that once relied on using horseshoe crabs as bait are declining, and there are viable alternatives for using their blood in medical products. Therefore, killing these creatures is unnecessary.

Blue blood being extracted from horseshoe crabs before they are returned to the shoreline.

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Scientists have confirmed that there are alternative methods to testing for toxicity using horseshoe crab blood. These options have been available for 15 years and rely on man-made substances. If these alternatives were implemented worldwide, it could potentially eliminate the practice of using horseshoe crab blood. However, only a small number of organizations, like Eli Lilly, have chosen to adopt these synthetic tests, as there was no pressure from regulators for companies to switch methods.

The introduction of new regulations from medical governing bodies, which establish standards for medicine quality and authenticity, has sparked optimism that tests utilizing traditional horse blood may be discouraged and substituted with ones that utilize synthetic components.

Recent actions by the European, Japanese, and Chinese pharmacopoeias have implemented regulations in order to achieve this objective. It is anticipated that the US will follow suit and make a comparable decision soon.

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Niles stated that altering the regulations will likely be beneficial, but there is still a need to convince companies to adjust their methods and preserve the horseshoe crab. This cannot happen immediately.

True blue test

Horseshoe crabs evolved around 450 million years ago, long before the appearance of dinosaurs. There are four species: three from Asia and one that lives along the east coast of North America. The last is the main source of crabs for bleeding.

Horseshoe crab blood contains highly reactive cells that respond strongly to harmful bacteria. When these cells encounter foreign microorganisms, they create clots to shield the rest of the crab’s body. This process was used by researchers in the 1970s to create the limulus amebocyte lysate (LAL) test, which can detect the presence of dangerous bacteria in medical products like vaccines.

Every year, hundreds of thousands of horseshoe crabs are captured in order to obtain the necessary blood for conducting tests. The crabs are then released back into their natural habitats after the extraction process. In 2021, it was estimated that out of 718,809 crabs collected, around 112,104 died, accounting for roughly 15% of the total. However, some conservation organizations argue that the death toll could be as high as 30% or more.

Larry Niles, a wildlife biologist in New Jersey, stated that taking half of the blood from each crab is excessive. He expressed concern about the large number of crabs being killed and the negative impact this has on the ecosystem, as other animals rely on the horseshoe crab’s eggs as a food source.

Source: theguardian.com