A Horseshoe Crab Just Saved Your Life
If you’ve ever had an injection (say the COVID-19 vaccine, for example), chances are a horseshoe crab was involved. More on that in a bit…
Horseshoe crabs are one of the most fascinating and ancient creatures on earth. These prehistoric-looking animals have been around for over 450 million years and have survived numerous mass extinctions. They’ve been here longer than dinosaurs! Since their DNA has shifted so little in such a long period of time, they’re sometimes called “living fossils”. Today, 4 species remain, including the American horseshoe crab, found along the Atlantic coast of North America and the Gulf of Mexico.
Despite the name, horseshoe crabs are not actually crabs at all, but belong to a separate class of animals more related to scorpions, spiders, and ticks. They have a hard exoskeleton called a carapace and a distinctive horseshoe-shaped shell, which protects their body from predators. They even have 10 eyes, including 2 compound eyes on the sides of their shell and a series of photoreceptors in their tails. Speaking of those tails, the dagger-like “telson” looks quite dangerous, but shouldn’t scare you. It isn’t particularly sharp and not at all poisonous and is used by the horseshoe crab to right itself if it gets flipped over on it’s back. “But wait!” you might be saying. “What about the part where a horseshoe crab saved my life?” Let’s skip ahead to that part.
Horseshoe crab blood is an incredibly important ingredient in the medical industry. The milky blue blood is used to test vaccines, medicines, and surgical equipment for endotoxins, a harmful bacteria that can trigger a range of immune responses in humans including fever, inflammation, and shock, and can cause damage to organs such as the liver and kidneys. The blue blood contains a unique compound called Limulus Amebocyte Lysate (LAL), which is highly sensitive to endotoxins. It is so coveted that a gallon of horseshoe crab blood is said to cost more than $60,000!
Due to the importance of horseshoe crab blood in the medical industry, there are concerns about the sustainability of the horseshoe crab population, as their blood is often harvested for this purpose. However, efforts are underway to develop synthetic alternatives to LAL and reduce the need for horseshoe crab blood in medical testing.
But horseshoe crabs are an incredibly important part of the ecosystem. Their eggs provide a vital food source for migratory shorebirds, and their shells provide a habitat for small animals and plants. While only an estimated 10-30% of horseshoe crabs die when their blood is harvested, scientists don’t quite know exactly how the process impacts these creatures and many conservationists are worried about their future. Horseshoe crabs are also under threat from habitat loss and overfishing. Their populations have declined significantly in recent years, and some species, like the Asian horseshoe crab, are listed as endangered. Conservation efforts are underway to protect horseshoe crabs and their habitats, but more needs to be done to ensure their survival.
In our Nature Links class, we learned about horseshoe crabs from their fascinating anatomy to their ancient DNA. We explored their importance in the medical industry and a friendly debate ensued about whether we should continue to harvest their blood to test vaccines and equipment. Participants argued thoughtfully on both sides and supported their reasoning with reflective explanations. Ultimately, regardless of which side students landed on, all agreed that horseshoe crabs are an incredibly valuable species to study and protect. By working to conserve horseshoe crabs and their habitats, we can help ensure that these incredible creatures will continue to thrive for generations to come.
