Horseshoe Crab Blue Blood + Paint Making

I really enjoyed Sasha Fisherman’s presentation and learned a lot of new information. I also appreciated Emma posting more information on horseshoe crabs. I previously knew horseshoe crabs are one of the oldest living species, but was unaware of their blue blood and how valuable it is. According to Carrie Arnold from National Geographic the lysate from their blood costs $60,000 per gallon. Horseshoe crabs are the only natural source of limulus amebocyte lysate, which detects endotoxin. Due to the Covid-19 virus, their blood has been in even more demand.


“Every year, pharmaceutical companies round up half a million Atlantic horseshoe crabs, bleed them, and return them to the ocean— after which many will die. This practice, combined with overharvesting of the crabs for fishing bait, has caused a decline in the species in the region in the past few decades” according to Arnold. 


In 1990, it was estimated 1.24 million crabs spawned in Delaware Bay and by 2019 only 335,211 crabs spawned due to over harvesting practices. I also thought it was interesting that they have nine eyes. I also know naturally occurring blue is rarer than other colors, so I was surprised to see how vibrant their blood was. It makes me really sad that horseshoe crabs have survived 445 million years, yet is currently endangered due to human practices. The American horseshoe crab is listed as vulnerable to extinction, the tri-spine horseshoe crab is endangered, and two Asian horseshoe crab species are expected to be on the Red List soon. These are the only four species left and only one is found in America. The photo of them harvesting their blood made me really sad and looks painful to the crab. I know their blood is important and saves lives, but I wish the synthetic alternative was more widely used. I truly hope the horseshoe crab stays alive and their whole ecosystem won’t collapse. 



I also really enjoyed making the blue paint and then using it! I used water and honey with mine. I noticed it took longer to dry than watercolors, but had a similar consistency to watercolor or acrylic depending on how much water I added. I also noticed after drying it had an interesting shine to it, which I liked. Although when drying it was still sticky and my pages and sleeve almost stuck to the paint. Overall, it was another fascinating week in class and I enjoyed the hands on paint making.