Lobsters have blue blood.
Lobsters Have Blue Blood (And It's Not Just Royal)
While humans bleed red, lobsters bleed blue—not because they're royalty, but because of hemocyanin, a copper-based protein that transports oxygen through their bodies. When copper binds with oxygen, it creates that distinctive blue color, making lobster blood look like it belongs in a sci-fi movie.
The difference between us and them comes down to metallurgy. Our red blood uses hemoglobin, which relies on iron to shuttle oxygen around. Lobsters and many other marine creatures evolved with hemocyanin instead, which uses copper. When you crack open a cooked lobster, that milky-white gel you see? That's the hemocyanin—it turns opaque and loses its blue color when heated.
Why Copper Instead of Iron?
In the ocean, copper is more abundant and accessible than iron. Evolution tends to work with what's available, and for marine invertebrates, copper was the winning ticket. But there's more to it than convenience.
Hemocyanin actually outperforms hemoglobin in cold, low-oxygen environments—exactly where lobsters live. While iron-based blood struggles in chilly deep water, copper-based blood keeps working efficiently. It's like having winter tires for your circulatory system.
The Blue Blood Club
Lobsters aren't alone in their aristocratic blood color. The blue blood club includes:
- Horseshoe crabs (whose blue blood is harvested for medical testing)
- Octopuses and squid
- Many spiders and scorpions
- Snails and other mollusks
These creatures all share the hemocyanin system, though they're not all closely related. It's a case of convergent evolution—different species independently arriving at the same solution.
From Ocean Floor to Medical Lab
Scientists are increasingly interested in hemocyanin beyond pure curiosity. Research suggests lobster hemolymph (the technical term for their blood) has anti-inflammatory properties and may help with skin regeneration. Horseshoe crab blood is already used to test medical equipment for bacterial contamination—a multi-million dollar industry.
So next time you're at a seafood restaurant, remember: that lobster on your plate had blood bluer than any human noble's could ever be. It's just chemistry, but it's pretty spectacular chemistry.