There is growing evidence that insects feel pain, just like us

We have long seen insects as instinctive mindless creatures with robotic responses to the world and all its impulses.

But the closer we look, the more we discover surprisingly complex behaviors, from bees communicating through dance to incredible feats of ant collaboration, and now we have mounting evidence that these tiny creatures that run our world can also experience pain.

Nociception – the sensory nervous system’s detection of unpleasant stimulation, including chemical burns, sharp cutting and bruising – causes a variety of physiological and behavioral responses in animals. One may be the perception of pain.

It is well documented that insects have avoidant reactions to potentially harmful contact.

In addition, experiments in 2019 revealed that the much-studied fruit fly, Drosophila, showed symptoms of chronic pain after researchers removed the fruit fly’s leg. When the fruit fly was completely healed, researchers found that the contralateral leg of the fruit fly became hypersensitive.

The authors traced this to the fly losing its “pain-braking” mechanism in its nerve cord. A pain-braking mechanism softens the perception of pain, but in the fruit flies, when the sensory nerves were overstimulated, the brake was turned off completely.

But since even bacteria stay away from unpleasant stimuli, detecting pain in another lifetime is not as simple as looking at a negative reaction to a harmful contact. To consciously register a feeling of pain, we need a complex physiological system that connects to our brains, and possibly even emotions.

In mammals, the nociceptors (pain receptors) send an alarm for bad stimuli to our brains, where neurons generate the negative and subjective, physical and emotional feeling of pain.

Studies show that nociception and pain can be regulated independently of each other, and have identified different systems for the regulation of each.

These systems have yet to be fully identified in insects.

“A hallmark of human pain perception is that it can be modulated by nerve signals from the brain,” neurobiologist Matilda Gibbons at Queen Mary University told Newsweek.

“Soldiers are sometimes unaware of serious injuries on the battlefield because the body’s own opiates suppress the nociceptive signal. We therefore asked whether the insect brain contains the nerve mechanisms that would make the experience of a pain-like perception plausible, rather than just basic nociception. “

Gibbons and colleagues went through the scientific literature and found several pieces of evidence suggesting this mechanism is present in insects.

While they lack the genes for the opioid receptors that down-regulate pain in us, they produce other proteins during traumatic events that may serve the same purpose.

Behavioral evidence also suggests that insects have molecular pathways that suppress responses to noxious contact, both for their peripheral and central nervous systems. For example, the presence of a sugar solution suppresses the normal avoidance of unpleasant stimuli by bumblebees.

Anatomically, insects have neurons descending from the brain to the part in their nerve cord where their defensive response against noxious touch originates.

In addition, the tobacco hornworm even uses soothing behaviors after being injured, such as grooming.

Each of these things may not be definitive on their own, but together they seem to indicate that insects have some sort of pain relief system, similar to ours.

“We argue that insects most likely have central nerve control over nociception, based on behavioral, molecular and anatomical neuroscience evidence,” the team concluded in a statement. “Such control is consistent with the existence of pain experience.”

However, since insects are a large and diverse group, it is quite possible that the complexity of their nociception regulation and potential pain sensations also differ widely between them.

However, the prospect of their pain raises important ethical questions for further research, especially in light of the proposed mass farming of these animals in the future.

“We are at an important crossroads in feeding a human population projected to reach 10 billion by 2050,” the researchers say.

“While conventional livestock farming is a major contributor to climate change, the United Nations is recommending mass production of insects for food. However, ethical implications have not been thoroughly considered, as animal welfare protections usually do not apply to insects.”

This research was published in Proceedings of the Royal Society B: Biological Sciences

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