Do insects feel pain?

Do insects experience pain as we do?

Pain is a sensory as well as an emotional experience and is therefore highly subjective.. This event is defined as an experience associated with a tissue injury but, curiously, sometimes pain appears as a physical symptom of an emotional maladjustment (somatoform disorder) without any specific physical trigger. Pain belongs to each individual, since the physical and emotional state of the individual plays an essential role in its perception, as well as his or her memories and previous experiences.

When it comes 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 feelings are difficult to record in measurable parameters and, in addition, all results are subject to the interpretation of the researcher. Humans can fall into the error of humanizing other living beings without realizing it, since they have no 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, many ethological questions and investigations can be raised that can be elucidated with anatomical markers. Today we address one of the most interesting that can be stated: do insects feel pain? Stay with us and find out.

Do insects experience pain?

All of us, to a greater or lesser extent, have been exposed to the invertebrate world at some point in our lives. These primitive beings seem practically "automatons", as they do not seem to mind losing a limb, half of their body or even their head.. Without going any further, any entomologist or curious person who has had the opportunity will have observed, with horror, how a grasshopper is devoured by a praying mantis while alive and, in the meantime, it 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 flee. The key is enclosed in the definition of the term itself: the rest of living beings do not have to perceive pain. At this point, it is essential to differentiate pain from nociception, it is essential to differentiate pain from nociception..

Pain is a personal, subjective and non-transferable experience that includes the integration of negative emotions. In nociception, on the other hand, nociceptors (pain receptors) process potentially harmful stimuli against tissues and send signals to the living being's nerve center to do something about it (if it has one). Most animals possess the capacity for nociception, but this does not mean that they feel pain per se..

If we get philosophical in 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 an insect's body, it flees from it because it has surface 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 things, the ultimate goal is to leave their genetic imprint in the form of offspring as many times as possible, so it is necessary to be able to perceive threats in order to survive as long as possible. If we do not assume the ability of the species to respond to environmental damage, the mechanisms of natural selection are impossible to explain..

Scientific evidence and the dilemmas of pain

Nociception is ubiquitous in the animal kingdom, but pain, not so much. This is a topic for another opportunity, since it has been demonstrated that rats, birds and other vertebrates can feel emotions beyond the basic ones, that is, those that respond to something more than a mere evolutionary mechanism.

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

• Must an animal be self-aware in order to perceive pain?
• What kind 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 things?

As you can imagine, answering these questions 100% reliably is, at this point in time, completely impossible.. The reality is that we do not know what it takes to go from nociception to pain, because it is a question as ethereal as the nature of life itself. However, science is not static, and as such, in the face of any question, possible answers are sought.

In this case, we will focus our attention on the scientific paper Nerve injury drives a heightened state of vigilance and neuropathic sensitization in Drosophilapublished in the journal Science Advances, in the year 2019. This publication attempted to to quantify the pain perceived by flies Drosophilawith 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 on one of the flies' limbs and then the lesion was allowed to heal completely. To the surprise of the professionals, it was discovered that, once the damage was received, the rest of the flies' limbs became hypersensitive.. It is believed that these invertebrates are "primed" to perceive pain on a smaller scale and thus be able to respond more readily to it on future occasions and maximize their chances of survival.

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

• You may be interested in, "What is Ethology and what is its object of study?"

The evolutionary meaning of pain

We could go so contentedly to sleep thinking we have solved the dilemma, but in the world of science nothing is ever that simple. That something has been discovered may point to a direction, but never establish a dogma, unless the observed reality is repeated in all cases. That flies Drosophila can feel pain or not is an open debate, but the reality is that we still do not have we still have no information from the vast majority of invertebrate taxa on this subject..

In addition, professionals from the Entomological Society of Canada offer an interesting final thought: what use is it to insects to perceive pain? Invertebrates have an extremely basic, but inexpensive nervous system. Having a nervous system like the human nervous system involves 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, it seems that the answer is no. They have nociceptors that allow them to flee a noxious stimulus as quickly and effectively as possible, so it is hard to think of reasons why they would benefit from a more complex perception of a harmful event. They already maximize their chances of survival with what they have, and so to allocate more resources on a more complex emotion seems evolutionarily unfeasible.

Summary

Again, we remind you that in this space we have not stopped moving in conjectures and digressions, because no matter how much data is obtained, it is always subject to the interpretation of who collects it. We do not even know what pain is in its entirety, so answering the question posed here with complete certainty is an impossible task.

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

Bibliographic references:

• Do insects feel pain? Societas Entomologica Canadiese. Retrieved April 2 from https://esc-sec.ca/2019/09/02/do-insects-feel-pain/
• Adamo, S. A. (2016). Do insects feel pain? A question at the intersection of animal behaviour, philosophy and robotics. Animal Behaviour, 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.