Some Invertebrates Also Feel Pain

For a long time, the international scientific community was not even willing to discuss the possibility that invertebrates may feel pain. For most creatures except octopuses, this was the general consensus. But lately, more and more experts are beginning to come up with proof that indeed insects and other such living things can feel pain. If this turns out to be true, analysts say that it will illustrate the innate bias that humans have towards “simpler organisms” which they consider “unworthy” of experiencing things such as pain, LiveScience reports.

Not one year ago, in the spring of 2009, the scientific community was put in a state of frenzy when experts announced that a certain species of crabs could certainly feel pain. Researchers from the Queen's University Belfast, led by expert Robert W. Elwood, and graduate students Mirjam Appel, determined that hermit crabs responded to painful stimuli in a manner similar to that exhibited by more complex creatures. Hermit crabs are those small crustaceans that live in seashells they salvage from the seafloor. In their experiments, small electrical shocks applied to the crab made the animal exit its shell, and start rubbing its abdomen at the exact location where the shock had been delivered. This is precisely the same type of response mammals, including humans, exhibit in similar circumstances.

In a new study from the same research team, it was additionally demonstrated that hermit crabs could not only feel pain, but that they were able to remember it as well and learn to steer clear of a pain source. The invertebrates were zapped with electrical shocks again, and then the researchers watched their behaviors. Elwood and Appel determined that the creatures were far more likely to begin inspecting nearby homes, as opposed to other crabs that were not exposed to shocks. The group also learned that animals which experienced the pain were very likely to abandon their old home altogether, and set out searching for a new one.

Until now, many scientists have been adamant in invoking reflex as the main explanation for such types of behavior in more simple creatures. The scientific community usually employs a strict set of guidelines when it comes to determining whether a living thing can feel a pain sensation or not. This set includes the creation of lasting memories of the pain source, which translates into the animal avoiding the same situation that caused it pain in the first place whenever possible. By this definition, hermit crabs can definitely feel pain, and other crustacean species probably do too. Details of the work appear in the latest issue of the respected journal Animal Behavior.