Research suggests that octopuses' pain is not just based on physical reaction but on their emotional response, too.
ScienceAlert reports that a particular study entitled "Behavioral and neurophysiological evidence suggests affective pain experience in octopus" specifies that the said animals are likely to feel and react to pain the same way as mammals do. This is the first strong evidence for this capability in invertebrates.
The feeling of pain is far more than a mere reflex to dangerous stimuli or injury. Rather, it is a multifaceted emotional condition that leads to either suffering or stress.
While vertebrates are perceived to experience both emotional and physical aspects of pain in general, it has yet to be resolved if invertebrates, characterized as having much simpler nervous systems, have the same capacity.
Octopuses' Potential for Feeling Pain
Essentially, octopuses are considered the most neurologically complex invertebrates on this planet, and yet, surprisingly, few studies have concentrated on their potential for feeling pain.
San Francisco State University Neurobiologist Robyn Crook, who has been exploring this issue for years, the most recent work from her lab has now utilized similar protocols for examining pain in laboratory rodents on cephalopods, particularly, the octopus.
Through the use of detailed measurements of spontaneous behaviors, as well as neural activity associated with pain, Crook has discovered three lines of evidence, all indicating animals have the ability to feel negative emotional states when they feel any pain.
These are similar characteristics exhibited by mammals, even though these said invertebrates' nervous system is organized in an essentially different manner to vertebrates.
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Octopuses are likely to feel and react to pain the same way as mammals do.
Reaction to Pain
Past research by Crook and others has found that octopuses are capable of reflexively reacting to noxious stimuli, learning avoidance of such harmful settings.
This particular study goes many steps ahead. Octopuses that were given an acetic acid injection into one arm after one training session in one three-chambered box exhibited clear avoidance of the chamber in which they were given the said shot. Those administered with non-harmful saline, on the other hand, did not exhibit any avoidance.
Moreover, when the invertebrates that had been injected with a painful shot were then given an analgesic called lidocaine, they tended to opt for the chamber in which they felt instant pain relief.
Those that were given saline only were found to have not cared less about the chamber where they were administered an analgesic.
This harm-free preference for a place is found to have been considered strong evidence of an affective experience of pain among vertebrates. Neither was that the lone parallel.
Ability to Discriminate Between Qualities and Intensities of Pain
In their study, Crook discovered evidence too, that octopuses have the ability to discriminate between pain's different qualities and intensities in various areas on their bodies.
All octopuses in the study that were injected with acid exhibited grooming behaviors at the area of injection for the entire 20-minute training trial, taking out a small portion of their skin with their beak.
This changes to other research on peripheral pain reactions, where octopuses had their arms either cut off or crashed and proposes the acid injection is generating some kind of centralized reaction.
In mammals, constant pain is the result of sustained activity in the periphery, which then initiates changes in the long run, in either the spinal cord or brain.
The study published in iScience also specified that on the other hand, Cephalopods, depend strongly on their peripheral nervous system, and it remains unclear, the amount of that information is making its way to their central circuits.
A ReefMan YouTube video below shows how an octopus hunts for food:
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