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  • The horseshoe crab...it’s a living fossil that has called Earth its home for almost

  • half a billion years.

  • It’s outlived dinosaurs and survived mass extinctions and ice ages, but today it’s

  • facing a new threat.

  • Their adaptations have worked with the way the Earth has changed and it’s only in recent

  • years with humans bringing impacts to their population that they've started to have declines.

  • Rising sea levels, habitat loss and overharvesting all threaten the population.

  • But if youve ever had a vaccine, injection or a medical implant, then you might not know

  • that youve been relying on this prehistoric creature’s blood to save your life.

  • Now, after decades of waiting, a new synthetic solution could change all of that.

  • Here on our beaches on the Delaware Bay, it is a place that people are witnessing a phenomena

  • that they cannot see anywhere else.

  • It is the equivalent of the wildebeests crossing the Serengeti.

  • In May and June here on the Delaware Bay where we are right now, millions of crabs come out

  • on a high tide to lay their eggs about six inches deep in the sand, and they will stay

  • in the sand and hatch in about a month.

  • And horseshoe crab eggs are a really critical part of the ecosystem here.

  • If a single crab is laying almost 100,000 eggs, that is providing a food source for

  • shorebirds, for gulls, for fish, for terrapins and then all up the food chain for that.

  • And then what happens with the horseshoe crabs then trickles down to the whole ecosystem here.

  • They just have managed to evolve with the changing oceans and the changing land.

  • The reason this crab has been able to evolve for so long?

  • Its blue blood.

  • This copper-based blood contains special cells called amebocytes, which are extremely sensitive

  • to endotoxins.

  • These are contaminants released from the cell walls of harmful bacteria and they can cause

  • life-threatening fever or toxic shock.

  • As soon as the amebocytes detect any of these endotoxins, the blood clots around the intruder,

  • immobilizing it and protecting the crab from infection.

  • In the 1960s scientists found a way to harness this unique superpower to make sure our medical

  • supplies were free from contamination.

  • And it replaced slower, more unpredictable tests involving rabbits.

  • The formula is called limulus amebocyte lysate, or LAL, and relies on amebocytes taken from

  • horseshoe crab blood.

  • And so every year half a million crabs are collected along the Atlantic coast, as well

  • as across the eastern shores of Mexico and China.

  • A third of the crab’s blood is drawn before they're released back into the ocean.

  • It’s estimated that 15% of crabs collected die as a result of this bleeding process,

  • which could mean the loss of 75,000 crabs in the US every year.

  • An alternative was found, however, almost 20 years ago here in Singapore.

  • In the past say 20 to 30 years ago we managed to collect 30 pieces in one afternoon, but

  • now it is difficult to find even a few.

  • In the mid-'80s Professor Ding Jeak Ling needed LAL for work involving IVF embryos, but there

  • was a problem.

  • Singapore research was not very well funded.

  • So because the LAL was so expensive, we had to find a good way to understand how the horseshoe

  • crab blood works.

  • So, my research collaborator, also my husband, together with our research students, went

  • to the Kranji mudflats to look for horseshoe crabs, and to bring a few samples back to the lab.

  • We cleaned them, we tagged them, and we took only a small volume of the blood, isolating

  • the blood cells from the horseshoe crab and we could produce our own equivalent of LAL.

  • This synthetic equivalent is called recombinant factor C, and it’s a clone of the main gene

  • in a horseshoe crab’s blood, which is sensitive to bacterial endotoxins.

  • It was a moment of realization that it is going to change the biomedical industry, and

  • it's going to save a very, very highly threatened species.

  • But the pharmaceutical companies didn’t come around as quickly as Professor Ding had hoped.

  • And so years and then decades passed.

  • We're a highly regulated industry.

  • And to say we would like to market a new medicine... a lot of people are reluctant to take a chance

  • on trying something new.

  • That’s until a scientist at pharmaceutical company Eli Lilly with a particular hobby

  • came along.

  • Birding is a hobby of mine, so to go to Delaware Bay and see the horseshoe crab spawning, it

  • kind of put it all together for me.

  • So the horseshoe crab is a keystone species in its ecology obviously for its own sake

  • but then for a lot of other animals that depend on it.

  • If we use RFC then there aren't any crabs that are affected, whether it's mortality

  • or whether there's some behavioural effect by taking the blood.

  • Studies have shown that the RFC test is a more effective and a potentially cheaper solution

  • than LAL.

  • Changing minds, however, remained the biggest challenge.

  • There's been several times I was ready to throw in the towel.

  • So it's been a difficult journey: to fight internally, to fight externally.

  • Nobody likes change but we think we're doing it for the right reasons.

  • We have had success and we have the data at the end of the day.

  • Persistence paid off, and in 2018, the first drug to use the recombinant factor C test

  • was approved by the FDA, and Eli Lilly is planning to transition 90% of its tests to

  • the synthetic by the end of 2020.

  • I think the consequence, if industry carries on with bleeding crabs, is at some point there

  • won't be any.

  • So there are real impacts to what we're doing and the longer we say, you know, they'll be

  • available forever...

  • It's likely not true.

  • It is important that we as humans are playing a role in protecting biodiversity and not

  • impacting biodiversity.

  • The synthetic version of the horseshoe crab lysate used by pharmaceutical industry is

  • going to have a major impact on horseshoe crab conservation.

  • It's not the only factor that we need.

  • We also need to continue with harvest limits and with beach restoration.

  • But reducing the need to harvest crabs for the use of their blood will have a major impact.

The horseshoe crab...it’s a living fossil that has called Earth its home for almost

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這隻螃蟹的血可能救了你的命 (This Crab's Blood May Have Saved Your Life)

  • 6 1
    林宜悉 發佈於 2021 年 01 月 14 日
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