Science & Technology Article

Reflections on the Atlantic Horseshoe Crab

Miriam Guest - Associate Principal Scientist
AstraZeneca

In 2016 the International Union for Conservation for Nature and Natural Resources (IUCN) published the news that the Atlantic Horseshoe crab was considered a vulnerable species(1). I wanted to understand what this really meant, as I knew we relied on this wild animal, to demonstrate a critical safety aspect of our injectable drugs.

Endotoxins are a risk to patient safety, as when injected they can cause a response in varying severity; we have to ensure our injectable products are free from endotoxins and the most recognised method uses Limulus amoebocyte lysate (LAL) which is a reagent manufactured from the blood of the horseshoe crab.

Atlantic horseshoe crabs cannot be farmed and live off the East Coast of the United States.

I reached out to the suppliers of both the traditional LAL products and alternative technologies that are available; what came back was a completely polarised message.

At one end of the scale some suppliers were telling me “the crabs are doomed” and at the other end of the spectrum the message was “they’re fine, they’ve survived 400 million years and they’ll survive this”.

In all honesty, with such a conflicting view, it was hard to trust the information; I needed to understand this for myself and very quickly I found this issue was more complex than it seemed.

Deep Dive Into the Numbers

Fortunately, my daughter’s lengthy music lessons gave me a lot of time to read and think about this.

As scientists we like to make decisions based on data and facts, but with moral judgement there will always be emotions. While you’re reading this, I want you keep in mind the seafood industry; the UK’s national dish has been fish and chips for over 100 years; both cod(2) and haddock(3) are considered “vulnerable” by the IUCN.

During those music lessons, I took a deep dive into fishery and IUCN reports, as well as journals on ecology and biodiversity.

In the figures outlined in the 2016 IUCN article the horseshoe crab, as a total population on the East coast of the United States, was in decline. However, the recently published Atlantic States Marine Fishery Report (ASFMC, May 2019), demonstrates that the overall population is now stable(4). When you scrutinise the recently published ASFMC Report it is clear that in some areas the population is thriving. More interestingly, the areas where the numbers are thriving are where there are lysate suppliers.

The figures suggest that the bait industry and coastal development are impacting the species. Whilst the lysate suppliers remove around 600,000 crabs per year, they are handled with the upmost care whilst taking a small portion of their blood and return them safely to the water afterwards; whilst it is difficult to quantify a mortality rate, it remains between 5% and 15%. In stark contrast, over one million Horseshoe crabs a year are fished and used as bait, removing them permanently from the oceans.

Biodiversity is important and all species have an important role to play; and we must consider that in the grand scheme of things when we’re looking at habitats and considering population numbers.


One species that is often discussed alongside the Horseshoe crab is the Red Knot(5). This shorebird has a broad migratory range and during the spawning season, will feast on the crab’s eggs in Delaware Bay, New Jersey. To support the Red Knot, a moratorium on Horseshoe crab harvesting has been in place for a number of years in New Jersey. The birds travel up to 9,000 miles in their annual journey to the Arctic breeding grounds. What has been observed in the short term is that the crab numbers are increasing in this location. However, it is not clear if this is reflected in Red Knot numbers; this illustrates the complexities of conservation. Coastal development is a huge threat to biodiversity; many species are impacted including Horseshoe crabs, the Red Knot and other shore birds; historical spawning sites for Horseshoe crabs are being lost as a result. Bulk heading of coastlines is also creating irreversible problems which will impact the success of any shore dwelling species.

What can we do?

We have established that keeping the value in the crab is what will protect it, but there needs to be a balance between retaining its value, while not exploiting it.

We could do nothing; that is a choice, but not one I’m comfortable with. What we can easily do within AstraZeneca is significantly reduce the amount of crab blood we use. There are several ways we can achieve that, and if we combine those methods, we can reduce our lysate use by over 95%.

· AUTOMATION of testing would result in a significant reduction in waste; it reduces invalid tests that need repeating and sees us reduce our lysate volumes. Automation also saves a lot of time in our labs, making them more efficient.

· STREAMLINING TESTING plans increases the number of tests per run, reducing lysate used in established methods; however, there is a risk of increasing invalid runs.

· MICROFLUIDIC TECHNOLOGY is the biggest win here; attach automation too and you can be incredibly efficient in the lab. This will lead to a 95% reduction in lysate, but as ever it’s more complex than that. By eliminating waste we expect to see a 99% reduction in lysate volumes at one of our high-volume sites.


There is a place for SYNTHETIC alternatives to help minimise the impact and reduce lysate use.

Personally, I had to do a lot of my own research, I needed to get deep in the numbers; this took almost a year of balancing different sources of information to try and find the unbiased data and facts. I had support and discussions with our Environmental group to verify the path we were taking truly was the Sustainable Option.

Things change, and I will be keeping a close eye on both the population dynamics and changes in technology; but right now, our solution is to keep lysate consumption to an absolute minimum.

But as I eat my fish and chips on a Friday night, I believe that right now, the best thing we can do to keep the crabs safe is to keep them useful.

References

1. Smith, D.R., Beekey, M.A., Brockmann, H.J., King, T.L., Millard, M.J. & Zaldívar-Rae, J.A. 2016. Limulus polyphemus. The IUCN Red List of Threatened Species 2016: e.T11987A80159830.

2. Sobel, J. 1996. Gadus morhua. The IUCN Red List of Threatened Species 1996: e.T8784A12931575.

3. Sobel, J. 1996. Melanogrammus aeglefinus. The IUCN Red List of Threatened Species 1996:

4. Jacobson, L., Carmichael, R. & Cieri, M. 2019 Horseshoe Crab Benchmark Stock Assessment Peer Review Report. Atlantic States Marine Fisheries Commission

5. BirdLife International 2018. Calidris canutus. The IUCN Red List of Threatened Species 2018: e.T22693363A132285482.