A horseshoe crab has probably saved your life. If you have ever had an injection, it will have been tested to make sure it is free from potentially deadly endotoxinsThese toxins are found in some bacteria, like E. coli and salmonella, and are very difficult to detect. Limulus amebocyte lysate, extracted from the horseshoe crab blood, reacts to these toxins allowing scientists to detect them in medicines and medical equipment.. The test uses a rare substanceLimulus amebocyte lysate (or LAL). only found in the milky blue blood of these prehistoric arthropods. Now, as scientists race to find a Covid-19 vaccine, this life-saving creature is under threat.

Despite its name, the horseshoe crab is not actually a crab, but a marine relative of spiders and scorpions. But whilst its land-dwelling cousins evolved into 100,000 different species, this sea creature remained virtually unchanged for 450 million years. It has survived several mass extinctions and has preserved an ancient biology that turns out to be essential for modern medicine.

But this great survivor now faces its biggest challenge yet: humans. "When you think about it," says conservationist Barbara Brummer, "your mind is boggled by the reliance that we have on this primitive creature." Each spring, hundreds of thousands clamber out of the Atlantic Ocean to lay their eggs on beaches in the United States. Technicians haul them off to laboratories, tap their blood, extract the precious lysateAt 48,000 per gallon, it is one of the most expensive liquids in the world. The most expensive is scorpion venom (over 30m per gallon), which is used to treat multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis., and return them to the sea.

However, research shows fewer and fewer are coming back. As many as 30% returned to the ocean are dying and, in Delaware Bay, their numbers have declined dramatically from 1.24 million in 1990 to only 335,211 today. Over-harvesting for fish bait and human activity on their spawning beaches have also affected numbers.

But so what? As long as there are enough to keep our drugs safe, human lives are surely more important than the humble crab?

Biologist Larry Niles disagrees. This isn't just about crabs, he says. "It's about keeping ecosystems productive." The annual crab-egg bonanza in Delaware Bay supports fish, terrapins, and migratory birds, all of which are in decline. And the birds - red knots and ruddy turnstones - are the biggest concern. They refuel on horseshoe crab meat during their epic 9,000-mile migration from South America to the Arctic.

If the migratory birds die out, there will be knock-on effects in ecosystems on opposite sides of the planet. Conservationists fear we are already living through a man-made sixth extinction, which threatens life on Earth and our own survival.

So, it is essential we conserve these ancient animals - as well as find synthetic alternatives to naturally sourced medical substances. Some believe that advances in genetic engineering, synthetic biology, and nanotechnologyAs digital technology and robots get smaller and smaller, scientists are designing electronic tattoos to monitor patients, injectable sensors, and nanobots to help with post-surgery recovery. are leading to a revolution in our relationship to nature. But, at the same time, biologists are scouring rainforests for undiscovered plants with medicinal properties.

Now, the disastrous impact of Covid-19 and the sacrifice of the horseshoe crabOften referred to as "living fossils" because they have changed very little over the last 450 million years. Two-feet long with nine eyes, armoured carapace and a spined tail, they are one of evolution's strangest survival stories. Other prehistoric animals still alive today include the duck-billed platypus, the crocodile, and the cow shark. reminds us how dependent we still are on the natural world. Even in the sterile, hi-tech labs working on a Covid-19 vaccine, a prehistoric arachnid is saving lives.

Some say, no, we are becoming less dependent on nature. For over a hundred years, modern technology has been substituting natural materials for man-made alternatives. From nylon and plastic to synthetic bacteria and nanomedicine. Within another hundred years, we will have left nature entirely behind - which will be good news for us, the planet, and the horseshoe crabs.

Others say, yes, we are part of the natural world and should never forget our dependence on it. The planet is one giant interconnected ecosystem that supports 8.7 million species and there are 10,000 different organisms alone in the human body. It is simply science fiction to imagine we can separate ourselves from the rest of nature. Instead, we need to better understand ecosystems and how to protect them.

Endotoxins - These toxins are found in some bacteria, like E. coli and salmonella, and are very difficult to detect. Limulus amebocyte lysate, extracted from the horseshoe crab blood, reacts to these toxins allowing scientists to detect them in medicines and medical equipment.

Rare substance - Limulus amebocyte lysate (or LAL).

Precious lysate - At 48,000 per gallon, it is one of the most expensive liquids in the world. The most expensive is scorpion venom (over 30m per gallon), which is used to treat multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis.

Nanotechnology - As digital technology and robots get smaller and smaller, scientists are designing electronic tattoos to monitor patients, injectable sensors, and nanobots to help with post-surgery recovery.

Horseshoe crab - Often referred to as "living fossils" because they have changed very little over the last 450 million years. Two-feet long with nine eyes, armoured carapace and a spined tail, they are one of evolution's strangest survival stories. Other prehistoric animals still alive today include the duck-billed platypus, the crocodile, and the cow shark.