People are able to feel a wide range of pain from scratching your feet in the winter morning – from grief to hunger and perhaps worst of all. For invertebrates, pain considered a way to try to correct something that harms the body through a reflex. A new study, however, paints a different picture for pain perception in fish-punching octopuses one of the world’s most charismatic and intelligent invertebrates. The journal Eye-Science will feature a pre-proof of the journal that addresses the pain experience of octopuses in three parts. The first involves an octopus receiving three different treatments in three chambers of a tank and then they observe which octopus shows a choice for which chamber.
Octopuses give a painful injection of acetic acid or AA, avoiding the chamber in which it given – even if that chamber had previously been the desired hangout. A control painless saline injection used, which did not affect the chamber preferences of octopuses. Octopuses experiencing ongoing pain can transform their least favorite room into their favorite if they given pain relief in the form of lidocaine injections while they are inside. This avoidance or attraction to the chamber – associated with pain and pain relief, respectively – may indicate that octopuses have a negative sensitivity to pain, information that they can use to navigate their environment as a way to avoid that pain.
The next part asked if octopuses had a discriminatory attitude toward pain, whether they could differentiate the area of discomfort, or whether the behavioral response behaviors were systemic regardless of where the boo-boo was. Some octopuses again injected with AA in one arm, while others injected with lidocaine and saline. The AAs grouped because they showed a directed and sustained pain response when sorting the injected area with their dorsum. This grooming lasted up to twenty minutes and saw some animals remove the skin around the injection site.
Individuals who injected with the other two treatments did not respond or briefly created the injection site. The third and final part of the study drew interesting parallels between mammals and cephalopods. When mammals injure an organ, say, their claws, pain-related neural activity occurs in the central brain. This distant activity from the site of injury is also in cephalopods, and – to this day – is the only mammalian tectonic known to replicate this mammalian layer. A misconception in this context is that octopuses have unique brains that extend into their organs.
To test whether this method of processing pain could be observed in octopuses, the researchers followed electromagnetic recordings to determine where the neural activity had spread following the injection of AA, and continued this activity until the pain was undone with lidocaine. Certainly, the pain in the arm started a prolonged activity that stopped so quickly by the pain relief at the same site as the AA. There seem to be many octopuses with injured arms, but what does that mean?
“Together, these data provide strong support for the existence of a permanent, negative-feeling state in octopuses; the research authors wrote in the research paper that this neurologically complex invertebrate is the first evidence of pain experience in the clad. “The study authors wrote the research paper, which raises concerns about the proposed ideas for osteoporosis cultivation due to increased demand for their meat. “The presence of chronic pain experiences in cephalopods (and possibly other superior animals) as a result of tissue injuries raises significant concerns for both their welfare and interesting new questions about the evolutionary origins of pain experiences.”