Do insects feel pain?

Pain is both a sensory and emotional experience and, therefore, presents a highly subjective charge. This event is defined as an experience associated with a tissue injury but, curiously, sometimes the pain appears as a physical symptom of an emotional maladjustment (somatoform disorder) with no physical trigger concrete. The pain belongs to each one, because in their perception the physical and emotional state of the individual plays an essential role, in addition to their memories and previous experiences.

When it comes to going to the rest of the animal kingdom, quantifying the intensity of the sensations becomes even more complex. Ethology faces a series of dilemmas that are impossible to address on a day-to-day basis with complete accuracy, since the feelings are difficult to record in measurable parameters and, furthermore, all results are subject to the interpretation of the investigator. The human can fall into the error of humanizing the rest of living beings without realizing it, since they do not have a voice to tell us what they are feeling at any given moment.

In an effort to discover the neurological and physiological processes of the animals that surround us, we can raise many questions and ethological investigations that can try to elucidate with markers anatomical. Today we address one of the most interesting that can be stated: Do insects feel pain? Stay with us and find out.

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Do insects experience pain?

All of us, to a greater or lesser extent, have been exposed to the world of invertebrates at some point in our lives. These very primitive beings seem practically "automatons", because they do not seem to mind losing a limb, half of their body or even their head.. Without going any further, every entomologist or curious person who has had the opportunity will have observed, with horror, how a grasshopper is eaten by a living praying mantis and, meanwhile, nonchalantly feeds on the stem of a leaf.

If insects felt pain as we conceive it, this observable reality would be impossible. Agony and despair would seize any living organism that perceives such pain and, therefore, it would not be able to perform any physiological function beyond the attempt to escape. The key is contained in the definition of the term itself: the rest of living beings do not have to perceive pain. In this point, it is essential to differentiate pain from nociception.

Pain is a personal, subjective and non-transferable experience that includes the integration of negative emotions. On the other hand, in nociception, nociceptors (pain receptors) process potentially harmful stimuli against the tissues and send the signals to the nervous center of the living being to do something about it (if at all have). Most animals have the ability to nociception, but this does not mean that they feel pain per se.

If we get philosophical when following this train of thought, we can say that being able to perceive a harmful stimulus is not the same as feeling pain. When a harmful source is applied to the body of an insect, it flees from it, as it presents superficial nociceptors that encode an escape response.

This makes all the evolutionary sense in the world: if the animal stays in that environment for too long, it dies and will not be able to reproduce. For living beings, the ultimate goal is to leave their genetic imprint in the form of offspring the greatest number of times they can, so it is necessary to be able to perceive threats to survive as long as possible possible. If we do not assume the ability to respond to environmental damage by species, the mechanisms of natural selection are impossible to explain.

Scientific evidence and pain dilemmas

Nociception is ubiquitous in the animal kingdom, but pain is less so. This is a topic for another opportunity, as it has been shown that rats, birds and other vertebrates can feel emotions beyond the basic ones, that is, those that respond to something more than a mere mechanism evolutionary.

To answer the question of whether insects feel pain, it would be necessary determine the neurological and subjective components that enable the experience of this sensory event. Scientists must therefore ask themselves the following questions:

• Must an animal be self-aware in order to perceive pain?
• What kinds of functional connections does a nervous system require for pain to take place?
• What is the evolutionary benefit of being able to feel pain to living beings?

As you can imagine answer these questions in a 100% reliable way, to this day, it is completely impossible. The reality is that we do not know what it takes to go from nociception to pain, as it is as ethereal a matter as the nature of life itself. Now: science is not static, and as such, any question is tried to get possible answers.

In this case, we are going to focus on the scientific article Nerve injury drives a heightened state of vigilance and neuropathic sensitization in Drosophila, published in the journal Science Advances, in 2019. This post tried to quantify the pain perceived by flies Drosophilas, with the action of γ-aminobutyric acid (GABA) and other components of the nervous system responsible for the transmission of painful impulses.

The researchers performed localized nerve damage to one of the flies' limbs, and then the injury was allowed to heal completely. To the amazement of the professionals, it was discovered that, once the damage was received, the rest of the flies' limbs became hypersensitive. These invertebrates are believed to "prepare" to perceive pain on a smaller scale and, therefore, be able to respond more readily to him on future occasions and maximize your chances of survival.

Based on these findings, it appears that flies acquire a state of "hypervigilance" after the first injury. This, in a way, could be translated to experience a different type of pain based on their experiences and, therefore, it acquires a subjective charge. Something as simple as this could demonstrate an obvious step from simple nociception to pain.

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The evolutionary meaning of pain

We could go to sleep so happy thinking that we have solved the dilemma, but in the world of science nothing is that simple. That something has been discovered can point to a direction, but never establish a dogma, unless the observed reality is repeated in all cases. That flies Drosophila may or may not feel pain is an open debate, but the reality is that We still do not have information on the vast majority of invertebrate taxa in this regard.

In addition, professionals from the Entomological Society of Canada give a final thought to say the least: what good is it for insects to perceive pain? Invertebrates have an extremely basic but inexpensive nervous system. Having a nervous system like the human entails a series of extreme physiological costs (Our brain consumes 20% of the body's glucose and oxygen), so is it really worth it?

For insects, the answer appears to be negative. They have nociceptors that allow them to flee from a harmful stimulus as quickly and effectively as possible, so it is difficult to think of reasons why they would benefit from a more complex perception of an event harmful. They already maximize their chances of survival with what they have and, therefore, allocating more resources on a more complex emotion seems evolutionarily unviable.

Resume

Again, we remind you that in this space we have not stopped moving in conjectures and ramblings, Because no matter how much data is obtained, these are always subject to the interpretation of who they are. pick up. We don't even know what pain is in its entirety, so answering the question posed here with complete certainty is an impossible task.

What we can affirm (based on physiological evidence) is that, if insects feel pain, it is clear that they do not do it in the same way that we do. A more primary and basic nervous system, by definition, must carry a different level of perception than ours. From here, the reflections and ramblings are endless.

Bibliographic references:

• Do insects feel pain? Societas Entomologica Canadiese. Picked up on April 2 in https://esc-sec.ca/2019/09/02/do-insects-feel-pain/
• Adamo, S. TO. (2016). Do insects feel pain? A question at the intersection of animal behavior, philosophy and robotics. Animal Behavior, 118, 75-79.
• Eisemann, C. H., Jorgensen, W. K., Merritt, D. J., Rice, M. J., Cribb, B. W., Webb, P. D., & Zalucki, M. P. (1984). Do insects feel pain? —A biological view. Experientia, 40 (2), 164-167.
• Harrison, P. (1991). Do animals feel pain?. Philosophy, 66 (255), 25-40.
• Khuong, T. M., Wang, Q. P., Manion, J., Oyston, L. J., Lau, M. T., Towler, H.,... & Neely, G. G. (2019). Nerve injury drives a heightened state of vigilance and neuropathic sensitization in Drosophila. Science advances, 5 (7), eaaw4099.