Do Worms Feel Pain? (Can Earthworms Sense Painful Stimuli?)

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Worms can actually feel all kinds of things, but whether worms feel pain is actually up for debate in the scientific literature (with more studies leaning towards the conclusion that yes, worms do feel pain).

For example, it is known that worms react to various types of stimulation. These include sensitivity to light, extreme temperatures and moisture.

Via their nervous system, a worm’s brain controls the active response of their body. This may be burrowing deeper to escape ultraviolet light, or seeker a cooler space.

But can worms experience pain, for example, will a worm on a fishhook feel pain when used as fish bait?

Yes, worms can feel pain according to most scientific evidence. However, it is not in the same way humans do. Their bilobal brains are simpler than the far more complex brains of other animals higher up the food chain. Whilst their brains respond to various stimuli transmitted via their nervous system, it is not thought that they react emotionally to pain.

Let’s dig a little deeper.

Do Worms Experience Pain? What the Science Says

There are actually mixed hypothesis’ and scientific evidence when it comes to worms feeling pain compared to human beings and other life forms with a higher cognitive capacity.

Studies Arguing That Worms Don’t Feel Pain

On the one hand, a study in Norway by Professor Wenche Farstad, concluded that worms and other such invertebrates don’t feel pain due to having less cognitive capacity and simple nervous systems (more on this study later on in this article).

Past studies also agreed and assumed that worms and other similar animals or smaller brained creatures don’t experience pain due to them not producing enkephalins or endorphins; chemicals that are normally released when we experience an especially potent stimulus.

Studies Arguing That Worms Do Feel Pain

This was rarely challenged until other studies, like the one by Swedish scientists, J. Alumets, R. Hakanson, F. Sundler and J. Thorell of the University of Lund, Sweden, reported different findings in a recent issue of the British journal Nature.

The scientists detected that worms DID in fact release these hormones as an automatic response to painful stimulus.

These hormones being released is one of the most fundamental traits of creatures with a comparatively high intelligence when pain is felt.

It was widely assumed animal intelligence meant feeling less or more pain and while a less intelligent creature will clearly deal with pain differently, it blurs the lines and gives food for thought.

An evolutionary psychologist, Dr David P. Barash, takes it one step further and offers a counterintuitive hypothesis (but valid) to the rest of the science available on this subject.

His argument is that we may have been wrong about our traditional evolutionary assumptions and that creatures like worms with “admittedly dim minds” and other unintelligent species could experience perhaps more pain as a result.

His evolutionary argument for this is the following:

“Isn’t it plausible that an unintelligent species might need a massive wallop of pain, to drive home a lesson that we can learn with less powerful inducement?” Dawkins asked.

The dummies, accordingly, would benefit more than the smarty-pants from an especially potent stimulus, a blast of something deeply unpleasant—call it “pain”—more likely to evoke whatever passes for memory and learning in their admittedly dim minds.

If so, then they would benefit from a particularly loud alarm bell: More pain rather than less.”

It’s a reasonable argument that negative stimuli should ring a crucial alarm signal in other animals with less cognitive capacity to REALLY drill home and remind them the danger to their survival when they experience pain.

Perhaps more pain than other life forms and animals that are more intelligent feel, thus they can avoid risk to their lives.

His theory makes sense; a more sensitive alarm system than that of an animal of more complex sentience would make sense from an evolutionary theory perspective.

It would certainly have some adaptive value to the creature.

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Other’s feel that Dr Barash’s hypothesis overlooks that the feeling of pain and suffering is more than a simple alarm bell.

Some have likened pain in a worm to an alarm going off in an “empty building”.

In the end, you’ll have to draw your own conclusion but it seems to be positively correlated that worms at least, do feel pain based on the evidence.

You may also have to have a deeper sense of what pain means to you and decide for yourself.

It seems clear that pain isn’t cross species universal, at least.

Does It Hurt a Worm to Be Cut in Half?

Yes, it is now accepted that worms feel pain – and that includes when they are cut in half.

Though it’s difficult to define pain and how they feel it compared to brainier animals.

It is not thought that they anticipate pain or feel pain as an emotional response. They simply move in response to pain as a reflex response.

They may curl up or move away, for example, from painful or negative stimuli as a survival mechanism and get away from more pain.

When cut in half, both parts may move. However, only the part containing the head has a chance of surviving.

If you’re wondering, do worms regenerate < we cover this in depth in this article.

Despite the worm’s very simple nervous system, never cut a worm in half – it’s never good for their well being and worms squirming aren’t doing it because they’re having fun!

Do Hooked Worms Feel Pain?

Not always – and there is a very interesting study behind this assertion.

Over ten years ago, the Norwegian government called for a scientific study to test whether or not invertebrates feel pain in a bid to decide whether to reform their laws on cold blooded, live bait.

Invertebrates cover a wide spectrum of animals including crabs and worms.

The study needed to take place in order to cover all aspects of Norway’s animal protection law – do worms actually feel pain when we use them for fishing, for example?

The study, led by Professor Wenche Farstad, concluded that most invertebrates feel no pain due to their very simple nervous systems.

He stated that crabs cooked in boiling water, just like live worms used as fish bait, did not feel pain and therefore people should feel no particular responsibility for their physical reactions to the boiling water nor the worms squirming.

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They concluded that red wigglers only display reflex curling on the fishhook – and to an extent feel a natural physical reaction to the object impaling them – but due to their very simple nervous system, they cannot have felt pain.

The same rule, they argued, applies for crabs boiled alive.

However, it is important to remember that this is simply a scientific opinion.

In truth we may never truly know whether earthworms feel pain or not – however, some suggest that humans are right to feel bad about causing any animal suffering and that since the common earthworm is an animal, just like any other live worms, they deserve respect and care.

The Norwegian study is interesting as it appears to rally against some of what we know about the damage that people can inflict on animals.

However, research is still ongoing with regard to how invertebrates respond to pain, whether unlike mammals or not.

Do Worms Feel Love?

The answer seems to be ‘yes’ – to an extent. Believe it or not, there is also a study to back this up.

In September 2017, researchers from three establishments agreed that yes, worms display social behaviour and do indeed express love.

The word ‘feel’, however, implies a conscious emotional response.

At the University of Southampton, Porton Down and at Belgium’s KU Leuven, researchers established that worms display a parental form of love.

Experiments conducted on the small, one-millimetre long C-Elegans worm revolutionised their thinking! 

The worms studied displayed a pre-programmed sense of caring for their offspring. Researchers discovered the worms deliberately chose to lay their eggs in the same space as their food source.

This means that once hatched, offspring would share and eventually compete for food in the same dining area.

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Furthermore, the adult worm parents exhibited an intuitive reserving of some of the available food, instead of devouring it themselves. In other words, they appeared to be saving some food to share.

The scientists also revealed another significant and major discovery. It has long been known that in humans, a hormone called Oxytocin influences social behaviour.

It is sometimes referred to as the ‘love hormone’.

In the worms studied, an equivalent nematode hormone was discovered. It is called ‘Nematocide’ – it functions in much the same way as the human hormone.

Therefore, the ‘loving’  behaviour of the worms was attributed, at least in part, to Nematocide.

Despite the absence of a complex brain with the capacity to display emotions, worm brains display ‘caring’ activities. It appears that these behavioural patterns are prompted by the release of hormones.

The studies suggest that worm parents also showed love by carefully choosing where to store their eggs.

This is something that appears to have taken genuine effort, and at least some form of innate care response.

To learn more about do worms have feelings and emotions, read our other in-depth guide.

Final Thoughts and Summary

The significance of all this research is very important.

Worms may be simple creatures, but research into how they react and behave show us that, to some degree, we all share some similarly fundamental traits.

Yes, we share similarities with even worms.

The experiments have also changed some of our perceptions in relation to the pain these creatures feel.

Whereas it was considered worms did not feel pain, we now can feel assured that they do as noted earlier from the scientific studies.

Worms may not feel emotionally stressed by pain, but what we do now know that injuring them, cutting them or hooking them likely hurts – and we can imagine.

This has led to many people moving away from live bait when fishing, and towards more careful worm conservation in the garden.

A worm’s brain may only be small, but despite the scientific study funded in Norway, it is a fair assumption that they will display more than only reflex curling if they are inflicted pain upon badly enough.

The final point to take away is, therefore, if you can, avoid hurting worms – they haven’t done a thing to deserve it.