Do Worms Have Blood (and Does a Worm Bleed?)

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The short answer to this question is, yes. Most worms do have blood, especially the earthworms you may find in your garden. The blood is usually red (a shade lighter than humans), pink, colorless and can even be green.

If you accidentally injure an earthworm when you shovel your soil, you will find that the earthworm may also bleed red, just like us. 

However, the difference in the blood shed by earthworms is that it’s not quite as dark as ours, but a shade lighter. 

Since earthworms breathe through their skin, what is their blood circulation system used for?

The blood circulatory system of earthworms is a closed circulatory system. 

Like us humans, this circulatory system is confining blood within blood vessels; while the open circulatory system seen in insects, such as grasshoppers, means blood (body fluid) flows freely within the body cavity. 

There is a thicker main blood vessel on the back of the earthworm, also called the dorsal vessel. 

The purpose of the dorsal vessel is to send blood from the surrounding small blood vessels to the 5 heart areas near the head.

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Earthworms have a strong regenerative ability, even if the organs are cut. You can read more about what happens when worms are cut. 

Where is the heart of the earthworm?

Speaking of worms bleeding, we have to talk about the heart of the earthworm. 

The heart of an earthworm is located at the front end near the head, and it usually does not vary from one species to another. 

It is usually formed by blood vessels with 4-5 pairs of circular arterial “arcs”. 

These arterial arcs are located on both sides of the body. And this constricted artery is the heart in a sense. 

The contraction of the arterial arc will cause the flow of blood, and then the blood will push down and flow to the ventral vessel of the abdomen, and then flow back to the various small blood vessels.

After that, small blood vessels and capillaries will take nutritious blood to the various organs and cells, and finally flow to the dorsal blood vessels to complete the cycle. 

This forms the blood circulation system of the earthworm.

You can also find out what earthworms eat to nourish their blood.

Sometimes Earthworms Do Not Bleed

Some people have asked, if the earthworm was accidentally squashed or cut in half, there is usually no blood flowing out of it, or even if there was, it’s not that much. 

This is true and, in fact, it is because the blood content of the earthworm itself is low, which also results in low blood pressure. 

This means its blood flow rate is actually not very fast and naturally, it will not spray out (unlike a cut in a human artery, where the high blood pressure means blood sprays out).

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It’s not that the small blood vessels in an earthworm do not bleed, but the larger one bleeds more. 

If you hurt the arterial arc close to their head, the chance of bleeding is higher. 

If you accidentally cut the earthworms back further towards the tail, then you don’t have too much bleeding (obviously, we’re not telling you to test this. Treat your worms with the compassion and respect they deserve).

We’ve also talked here before about the powerful regenerative ability of earthworms that can heal most injuries below the head. 

An earthworm’s regeneration capability depends on the damage taken (if it is divided into two, the tail portion is more likely to die), where the location of the cut is and the seriousness of the damage to each organ.What did earthworms do, and why are earthworms a pest ? the reason.