Not all animals have red blood. In fact, the blood in animals can have other colors like blue, green, yellow, purple, and even white!
These colors caused by different proteins and pigments found in the blood. They all serve different purposes like enabling the animal to survive in seawater below freezing point at the South Pole.
When we take a look at these strange animals it’s hard not to get amazed! The variety of species and the level of sophistication is just fascinating.
Before we dive in you should prepare yourself for some technical terms and some nerdy stuff. These colors are not easy to explain so we will have to take a closer look at some proteins.
But worry not, we will explain everything in plain English 🙂
Why Do Animals Blood Have Different Colors?
In nature, we find that block comes in a wide variety of colors. But why? Let’s take a look at what causes blood to have a certain color in each animal.
Some animals have a special mix of plasma proteins in their bloodstream. These proteins cause the many colors of the blood.
This can cause the blood to have a light blue color for instance. This blue color is derived from copper proteins called hemocyanin. Other animals will have another protein (with a higher concentration of iron for instance) which will cause the blood to turn red.
Special blood for extreme cold water
Animals who live in the extremely cold waters around the North and South Pole have been observed to have special colored blood. This is caused by a high concentration of a special type of protein which enables the blood to oxygen in cold temperatures.
This is the case with the big Antarctic octopus called Pareledone Charcoti.
The specific species of octopuses have around 40% or more hemocyanin in its blood to be able to live in the cold waters of the Antarctic.
Which Animals Have PURPLE Blood?
We also found quite a lot of animals with purple blood which can look almost purple.
This protein also helps marine animals to fight infections. It helps worms regenerate when a part of it is cut off. You might know that worms can regenerate when a part is cut off and scientists believe the hemerythrin plays a vital part in that process.
These worms are known as Peanut Worms. They have blood that is dark purple and can appear almost black.
You can actually see the purple color of the blood because they have semi-transparent skin!
Brachiopods also have dark blood.
The purple color comes when the blood is oxygenated. Otherwise, the blood is almost transparent. The blood circulates when the tiny heart pumps it around in the animal.
The blood circulates to deliver nutrients to the animal.
Which Animals Have BLUE Blood?
As we mentioned above, the blue color in animals blood comes from a higher level of cobber (hemocyanin) in the blood.
The oxidized copper in the blood protein gives the blood molecules a blue color. The oxygen levels are controlled by temperature and the heart is located in the back of the stomach.
When the blood is oxygenated it turns blue. Otherwise, it is colorless.
The hemocyanin protein is a lot bigger than other blood proteins (like hemoglobin in human blood) and there it flows freely around in the blood of these animals.
Spider blood is pale blue because of hemocyanin.
The spiders also use the blood pressure to get rid of old skin (shedding) and that’s a vital part of the life circle for some spiders.
The Horseshoe Crabs have blood that is light blue. That is also due to the cobber-based hemocyanin in its blood.
The Horseshoe Crabs have an impressive level of resistance to bacteria. This is also one of the main reasons why it has survived for so many years. Some scientists believe that the Horseshoe Crabs have survived for more than 400 million years.
It also has no veins as the blood runs through an open circulatory system where it has direct access to the internal organs. So the blood has faster and easier access to the organs and blood veins are not needed.
There are also some scorpions with blue blood. One, for instance, is the Emperor Scorpion.
It is the largest among the scorpion family. They have high levels of hemocyanin in their blood as well.
Some Octopus Species
As mentioned above we also find some special octopuses around the south pole with blue blood.
Again the reason is the same. It’s due to the high concentration of copper-based proteins in the blood.
Which Animals Have GREEN Blood?
We also find animals with green blood. These are typically lizards and worm-type animals.
The green color is caused by a pigment called Biliverdin. It is the same pigment that will sometimes turn your skin green when you have a wound or took a hit. As you know, an eye can get really colorful if it is hurt.
It is the same pigment that makes the beautiful Tobacco Hornworm bright green:
Almost all the animals with green blood eat green vegetation. So it could indicate a connection but it has yet to be found. Maybe they just love the green color so much that they are attracted to the green vegetation 🙂
Here’s another strange animal for you. The skink belongs to the lizard family.
The skink also uses hemoglobin to carry the oxygen around in its body. And the hemoglobin causes some by-products (biliverdin among others) which are normally excreted into the intestines.
But not with the Skinks.
They thrive with a high level of biliverdin in their blood and that causes the blood to turn green!
The green pigment is not only found in the blood of the Skinks. It is also present in the muscles and bones. Another reptile with green blood is the Prasinohaema which is a small green salamander found in New Guinea.
Leeches have blood containing the protein called chlorocruorin. It causes the blood to turn green.
It is another oxygen-binding protein found in the plasma of the blood. And mostly among creatures living in the sea. Sea creatures often have unique proteins in their blood to help them survive and regenerate.
When you think about Leeches you might think about their green blood color but your own blood. Many people are afraid of leeches because they have been portrayed as bloodsucking animals.
They are predatory blood-sucking parasites.
They are quite unique because they have sucking mechanisms on both ends. They have been used in treatments for sickness in the old days. What a bit of luck that we live in a modern time and age!
There are a lot of different species of Leeches and they all are different. Some are long and thin and some are shorter and bulkier. Most of them will only feed blood on small animals.
Which Animals Have YELLOW Blood?
When an animal has a high concentration off vanabin in the blood it turns yellow.
Scientists do not know why animals have these high concentrations of vanabin as it doesn’t help the circulation of oxygen. So that is still to be explored.
Beetles have yellow-ish blood like several other bugs.
You might have noticed this whenever big bug splashes again in the front of your car.
Many people don’t realize that insects typically don’t even have blood vessels. Instead, they have a large hole inside the skeleton where all the blood resides.
Sea Cucumbers are weird animals. They live down at the bottom of the ocean and are very simple animals.
They might look like fruit and the name doesn’t make it easier to categorize this as an animal. But it is an animal and is it quite remarkable. They have thousands of tiny feet as you can see at the picture above. It will move slowly at the bottom of the ocean.
Again, the reason for the yellow color is found in the proteins of the blood. It has a high concentration of vanabin which has yellow pigment.
One of the strangest facts about Sea Cucumbers is that they can change from male to female during their lifetime. It’s not possible to distinguish the males from the females from the exterior anyway.
Did you know that Sea Cucumbers also belong the list of animals with no brain?
Which Animals Have WHITE/CLEAR Blood?
The Ocellated Icefish
This special type of fish houses completely white (translucent) blood!
Just like that octopus, we just looked at before, it also lives around the cold Antarctic Pole. The reason why its blood is totally see-through is also found in the protein mix of the blood. It completely lacks the proteins hemoglobin and hemocyanin!
According to the scientist, Michael Oellermann from the Alfred Wegenar Polar Institute in Germany, cold water can hold much more oxygen than warm water. And because the water has enough dissolved oxygen the fish doesn’t need to carry hemoglobin. It will get its oxygen from the cold water.
On top of that, we also find another weird fact about the iced fish. It doesn’t have scales like other fish. Scientists believe that this enables the fish to absorb the oxygen directly through the skin.
Here is another picture of the Icefish. It’s a young Icefish larva:
In this larva state, it is easier to see how the internal organs are placed at the lower abdomen (stomach). The blood is still totally clear and transparent and looks almost white in this picture.
It has a huge heart and can pump the blood around at high pressure.
It can live in water that is below freezing temperature. Water can still be liquid below the freezing point when there are sufficient levels of salt dissolved in the water.
Insects can have very bright yellow blood that will often appear almost white.
The blood (also often called hemolymph when explained) can be clear and transparent or it can be more white and look more like watered milk.
Cockroaches are also known to have white blood and you will notice it when you smack them.
What Is The Function Of Blood?
Blood is the fluid that normally runs inside the veins of animals and humans.
It can be multiple colors, as we have seen in this article, and it has some necessary and basic functions in the body. The majority of the blood is plasma but we also find several proteins and other good stuff inside the blood. All these parts are vital for the animal and they are different from each animal. This is also part of the reason why we have so many different blood colors.
It transports oxygen and several nutrients around in the body. All these elements are vital for the survival of animals and humans.
Vertebrates have red blood cells that travel through veins and arteries. They do so in a closed system where the blood is inside the blood vessels at all times. These are creatures such as:
It is the hemoglobin levels (containing iron) that causes the blood to be red.
Some animals have another blood system as we mentioned above. Some animals even live without blood as we will look at below. These are more simple creatures with other ways of getting nutrients.
Which Animals Have No Blood?
There are in fact quite a lot of animals without blood. These are:
- Some types of worms
- Sea Anemones
The Jellyfish is a strange animal with no brain and it can actually eat and function well without any brain. Instead, it has a more simple sensory system and tentacles which can be used to transport food from the sea into its mouth.
Because the Jellyfish has no heart it also has no blood. It relies on nutrients from the water that surrounds it. Its tentacle arms catch the food that floats by naturally and it transports the food into its mouth in order to eat it. Here you can read more about how the Jellyfish eats.
The Corals look more like plants but corals are in fact animals.
They are amazing creatures that live deep down at the bottom of the ocean and they look like plants. But they do not produce their own food like plants (photosynthesis) so they can not be considered plants. So they are animals.
Corals have no blood because they get what they need from zooplankton and from tiny plant-like creatures that live and grow on them. These tiny plants produce photosynthesis and live in symbiosis with the corals.
Another type of animal with no blood in its body is the Sea Anemone.
Sea Anemones are also very special creatures. They might look more like plants at first glance but they are animals.
They contain toxins in order to paralyze their prey. They are typically not poisonous for humans except for a few species.
As they do not have blood they rely on other ways of getting nutrients. The arms you can see hanging from the top of the Se Anemone can catch small fish and other creatures swimming by. It will then transport the food into the mouth and keep it inside its body for a while in order to extract what it needs.
We have written a separate article about the Sea Anemone and other animals without brains.
Which Animals Have No Heart? Some sea creatures live without a heart. These are animals such as Jellyfish, Flatworms, Sponges, Corals, and Sea Anemones. Instead, they rely on other pump-like structures to circulate the blood. Or they have no blood at all like the Sea Anemones.
You can read this article that lists all the animals without a heart.
Some of the strangest animals we often find among the sea creatures. They can be animals without blood, or without a heart, or even without a brain.
The reason they can survive without much intelligence (and even without the heart) is that the water carries a lot of food around which they can catch. Often times they won’t even be conscious of hunting food. They will just eat whatever zooplankton or other dead animals are floating by.
Sources: National Geographic, Businessinsider, Wikipedia.