How Many Hearts Do Worms Have? Do Earthworms Have a Heart?

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Do worms have hearts? The answer is pretty complex – yes and a no. In one way, they have functioning hearts – but in another, they’re not really hearts at all.

Though their hearts are not the same shape as ours, they perform the same functions. Five aortic structures conduct the activity of their hearts, and these are located near the mouth.

They perform by contracting and releasing action in order to pump blood around all of the worm’s body parts.

The aortic arches found in the worm world are formed in pairs. This raises some questions about how many hearts a worm actually possesses.

Below we will take a more detailed look at how these blood-pumping organs perform in these little creatures.

How many hearts does a worm have?

No one really knows! Some people insist that earthworms have five hearts. Though they are not heart-like structures in the same vein as our own, the aortic arches still pump blood around their bodies.

Some feel that the aortic arches in worms should not be called hearts. Other people feel that as the aortic arches are formed in pairs, worms should be considered to have ten hearts.

Which side of the debate do you fall on? Keep reading and let’s see if we can help make up your mind.

Why do worms have 5 hearts?

Having five arch-like things enables the flow to be constricted and released in a sequential action.

Blood is propelled along the circulatory system along two long channels. These blood vessels are known as dorsal and ventricular vessels.

Whilst the primary function of the worm’s aortic arches is the same as other hearts, their physical structure is different.

The human heart works as a pump, with a strong muscular action, forcing blood from one chamber to another. The blood is drawn into the chamber and then expelled into the circulatory system.

Worm bodies don’t use a pumping action via muscles in chambers. Instead, they use a squeezing action to drive blood around their body.

Blood is circulated throughout the body of the worm via two elongated blood vessels.

Worm hearts suit their body shape and perform to satisfy the demands of their body length. As a far less complex body shape, the worm heart activity is less complex.

The sequential squeezing action of each aortic arch adequately operates to transfer oxygen in the blood. Thus aortic arches are a less complex shape but do the job well!

worm is looking happily at the heart

I heard worms have 10 hearts? Is this true?

Yes and no – it’s all about the aortic arches.

Some studies believe that worms have 10 hearts based on the arch pairs as discussed above. However, if you really want to dig down into the physiology of a worm, they don’t technically have hearts at all.

This can make things confusing. Ultimately, like humans, worms need oxygenated blood to be able to live and survive.

Their nerves, receptors are skin are very different to ours, however. That is why applying our own ideas of anatomy to theirs can be fairly complex.

Some studies claim that the idea of worms having ‘false hearts’ (the arches). When studying animals, this can be very useful in helping us understand how the deeper worm actually works.

Do worms have heart beats?

That depends – for example, earthworms certainly have heartbeats. Earthworms regulate their heartbeats in much the same way as people do, by nerve stimulation.

Unlike some annelids, this means that earthworm aortic activity resembles that of humans than that found in some other worms.

This was a surprising discovery about earthworms – it’s normally a function that you’ll find common to vertebrates.

That makes the humble earthworm and all its complex blood vessels that little bit more interesting.

Of course, if you accept the idea that a worm doesn’t have a heart at all, you can claim that these movements are simply pulsations.


For the sake of argument, a worm has a functioning blood system much like any other animal – this just happens to be a species that, while very simple on the surface, is actually quite a complex critter deep down.

The idea of a human heart system applying to a worm is a little bit redundant.

Worms have ten little pumps working hard to make sure their brain, muscles and other organs all receive the blood they need.

Does that mean they have ten heart circulatory systems? Maybe – the jury is out!