Do Sea Urchins Feel Pain? What do Scientists Say?

No, sea urchins don’t show any sign of feeling pain, which means they do not feel pain. Although scientists did not find concrete evidence of a sea urchin feeling pain, a few people still believe they do.

Is the quick answer confusing you? Then continue reading the article till the end. I will discuss the sensory neurons of sea urchins and share the results of various scientific research about marine creatures’ pain receptors.

What Are Pain Receptors?

Pain receptors are a group of sensory neurons that respond to tissue damage. They are widely distributed in the skin and send signals to the spinal cord and the brain to initiate pain when an animal gets hurt.

sea urchin feel pain

In other words, pain receptors are the reason why you feel pain. If an animal doesn’t have pain receptors, it will not feel pain, even if you hurt it.

Do Sea Urchins Have Pain Receptors?

No, scientists haven’t found any pain receptors in sea urchins. The disappointing thing is that there has yet to be much experiment on sea urchins’ sensory neurons.

However, from a few pieces of research, scientists have found four sensory neurons in sea urchins that react to touch, light, temperature, and chemicals.

Sea urchins are spiny invertebrates in the class Echinoidea. People used to think that invertebrates do not have any pain receptors; thus, they do not feel pain.

But today, there have been massive disagreements between scientists. While some scientists have noticed minor reactions to pain in crabs and a few other invertebrates, other scientists believe these reactions are due to facing shock inside the cells.

Hence, although the probable answer is that sea urchins don’t have any receptors, there is no concrete evidence to prove it.

Where Are Sea Urchins’ Sensory Cells Located?

Sea urchins’ sensory cells are located in their epithelium. To be more specific, you will find these cells in their spines, tube feet, and pedicellariae.

While sea urchins do not have any eye spots, these cells play a similar role and respond to different circumstances. For instance, sea urchins react negatively to lights and try hiding somewhere if they encounter flashes.

sea urchin feeling

Besides, they show different reactions to touches, water temperature changes, and chemicals.

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Do Sea Urchins Feel Pain? How Do They Respond to Pain?

Sea urchins do not respond to pain, which is why many scientists believe they do not feel any pain.

But is that a valid assumption? To understand that you first need to know how scientists determine whether an animal feels pain.

Some of the factors that help determine an animal’s pain reaction are:

a) Physical response

Observing their physical response is the most obvious way to understand if someone is feeling pain. For instance, how does your body respond when you feel pain? You will try to rub the spot or scream in agony. It means that you are in pain.

When you hurt an animal, its nervous system will send signals to the brain. It will result in various physical responses.

Scientists also try to hurt animals and observe their physical responses to understand whether they are feeling pain.

b) Long-term behavioral changes

If scientists fail to get any short-term response, they will try to find any long-term behavioral changes in the animal.

When we know something can cause pain, we will try to avoid it, which refers to long-term behavioral changes.

For example, if you feel pain after touching thorns, you will remember it and avoid doing the same thing. That’s because it is painful.

c) Anatomy

Another way to understand if the animal is feeling pain is to study its anatomy. Every animal needs a sensory system that stimulates pain when the tissue is damaged.

Now, the obvious question is whether the above test has been done on sea urchins and what the results were.

Sadly, only a few studies have been done on sea urchins. Based on those results, most scientists concluded that sea urchins might not feel any pain. They have not found concrete evidence that these creatures feel pain.

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Some of the reasons why researchers think that sea urchins do not feel any pain are:

d) No pain receptors

Scientists haven’t found any pain receptors in sea urchins or any sensory neurons that react to pain. That’s why it is not possible for sea urchins to feel pain.

e) Absence of brain

Sea urchins do not have any typical brain. Instead, they have a large nerve ring that connects all the sensory systems. As sea urchins do not have any brains, they cannot receive any signal from the sensory systems about any feeling of pain.

f) Not showing any response to pain

Lastly, the absence of a brain also makes sea urchins unable to show any reactions to pain. Hence, researchers say that sea urchins do not feel any pain.

Many people believe sea urchins feel pain but cannot show any reactions due to not having a brain. But there is not any evidence to prove such claims.

Do Sea Urchins Feel Pain When Eating?

No, sea urchins possibly cannot feel pain when eating. Although a few people may try to tell you that these marine creatures feel pain, they will not be able to prove it.

Most invertebrates or seafood do not feel pain when eating, which is why you can say they may not.

What Does Sea Urchin Pain Feel Like?

Sea urchins do not feel pain but can make you feel pain. Their spine carries venom that can cause pain, redness, trouble breathing, and even death.

Can Sea Urchins Hurt You?

Yes, sea urchins can hurt you with their spines. These spines have poisonous pedicellariae, which look like tiny claw-like pincers. If the spine gets into your skin, it will hurt you.

However, the good thing is that sea urchins do not attack humans. But they live in shallow water where humans swim or dive. That’s why people often step on these marine animals and get hurt by their venomous spines.

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Do Sea Urchins Have Nerves? How Is the Nervous System?

Yes, sea urchins have nerves. Interestingly, sea urchins have a central nerve ring instead of a central brain system.

sea urchin feeling

Typically, animals have a brain to function in their bodies. But sea urchins do not have any brains. Instead, they have a central nerve ring connected to this creature’s whole nervous system.

Frequently Asked Questions (FAQs)

What happens when a sea urchin dies?

When a sea urchin dies, it sheds off its spines and leaves only the test organ. If you have a dead sea urchin in your tank, it will spawn and rot out. It will also cause the death of other urchins if you do not clean the water.

Do sea urchins have emotions?

No, sea urchins cannot experience emotions as they do not have any brains. Although their nerve ring operates like a brain, it does not have the ability to feel emotion.

Do sea urchins have feelings?

Yes, sea urchins have limited feelings. They can feel light, temperature, and chemicals and react to them. However, sea urchins do not have any brains, which means they do not have emotions.

Do sea urchins have organs?

Yes, sea urchins have several organs. Esophagus, intestine, and spines may sound familiar to you.

From the anatomy of sea urchins, some of the organs found in sea urchins are:

  • Genital plate
  • Gonopore
  • Anus
  • Mouth
  • Hard plate with madreporite
  • Axial gland
  • Nerve ring
  • Gonad
  • Intestine
  • Ampullae
  • Test
  • Esophagus
  • Radial canal
  • Ring canal
  • Teeth
  • Aristotle’s lantern
  • Tube feet
  • Test plates
  • Spines


Sea urchins are one of the fascinating seafood. While scientists haven’t found any proof that these marine creatures feel pain, many people like to believe sea urchins have life and feel pain.

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