Octopuses have blue blood because it contains copper-based haemocyanin, helping them survive in low-oxygen deep sea environments.
Horseshoe crabs have blue blood, which contains haemocyanin, and plays a crucial role in their immune system, detecting harmful bacteria.
Many spiders have blue blood due to haemocyanin, allowing them to transport oxygen efficiently, even in their low-oxygen habitats.
Lobsters also have blue blood due to the presence of haemocyanin, which is more effective in cold, oxygen-scarce environments.
Peanut worms have purple blood, a rare occurrence due to a unique respiratory pigment called haemerythrin, which binds oxygen.
Brachiopods use haemerythrin, giving them purple blood, which allows them to thrive in low-oxygen aquatic environments.
Sea cucumbers have yellow blood due to vanadium-based proteins, a rare element that plays a role in their respiration.
Flatworms have colourless blood as they absorb oxygen directly through their skin, eliminating the need for respiratory pigments.