In fact, some creatures have blood that’s blue, green, or even clear! It’s fascinating to think about how different life can be across the animal kingdom.
Let’s take a friendly journey together to discover five animals whose blood isn’t red, and why their blood is a different colour.
1. Octopus – blue blood
Octopuses are incredible sea creatures known for their intelligence and eight flexible arms. One surprising fact about them is that they have blue blood. Their blood is blue because it contains a protein called hemocyanin, which has copper in it. This protein helps carry oxygen through their bodies, especially in the cold, deep waters where many octopuses live. The copper in hemocyanin turns blue when it binds with oxygen, just like iron in our haemoglobin turns red. This special blue blood allows octopuses to survive and thrive in environments that might be challenging for other animals.
2. Horseshoe crab – blue blood
Horseshoe crabs are ancient creatures that have been around for millions of years. They also have blue blood, thanks to hemocyanin, just like octopuses. But there’s something even more special about their blood. It contains substances that help detect harmful bacteria. Because of this, horseshoe crab blood is used in medicine to make sure vaccines and other medicines are safe for us.
3. Green-blooded skink – green blood
Skinks are a type of lizard, and some of them have green blood. These skinks live in places like New Guinea. Their blood is green because it contains a substance called biliverdin, which is a waste product that usually gets filtered out in other animals. In large amounts, biliverdin is toxic, but these skinks have adapted to tolerate it.
4. Peanut worm – purple blood
Peanut worms are small, soft-bodied creatures that live in the sea. They might not look like much, but they have purple blood. Their blood gets its colour from a protein called hemerythrin, which uses iron to carry oxygen, but in a different way than haemoglobin does in our blood. The purple colour appears when hemerythrin binds with oxygen.
5. Icefish – clear blood
Icefish live in the cold waters around Antarctica. They have clear or colourless blood because they don’t have haemoglobin at all. Without haemoglobin, their blood doesn’t turn red. So how do they survive without it? The cold water they live in holds more oxygen, and their bodies have adapted to absorb oxygen directly through their skin and other tissues. This unique adaptation allows them to live in icy waters where other fish might not survive.
