A spider's blood is blue.
Why is Spider Blood Blue?
Unlike humans, whose blood is red due to the presence of iron-based hemoglobin, spiders have a different respiratory pigment called hemocyanin. Hemocyanin utilizes copper, which gives their blood its characteristic blue color.
The difference in blood color is due to different metallic elements in the blood's respiratory pigments:
| Organism | Respiratory Pigment | Metal in Pigment | Blood Color |
|---|---|---|---|
| Humans | Hemoglobin | Iron | Red |
| Spiders | Hemocyanin | Copper | Blue |
| Horseshoe Crabs | Hemocyanin | Copper | Blue |
- Spiders are not the only creatures with blue blood.
- Other arthropods, like horseshoe crabs, also use hemocyanin and have blue blood.
- The presence of copper in hemocyanin results in the blue color, similar to how iron in hemoglobin results in the red color.
