New research focused on squid has revealed why pain may be essential to survival. A study published in Current Biology revealed that an injury caused the aquatic animals to be on high alert, which in turn helped them survive an attack by a predator.
If living beings must exhibit special instincts to come out on top in a survival-of-the-fittest world, pain encourages animals and humans to act on those instincts. Although the premise seems obvious, researchers say the theory hasn’t been tested until now.
Pain helps organisms survive by putting them on high alert, a study shows.
The study focused on the longfin inshore squid, which live predominantly in the Atlantic waters off the East Coast of the United States, and examined how it interacted with the black sea bass, a natural predator. To put the squid on high alert, researchers at the University of Texas Medical School at Houston (UT) injured each one by cutting off the tip of an arm. This type of injury is common in the wild.
A group of control squid were injured in the same way, but they received local anesthetic to numb any sensations of pain. Researchers wanted to make sure the squid were reacting from the pain, and not from any reduced mobility resulting from the injury. A second control group had no injuries and were perfectly healthy.
Then, the groups of squid were set up for the ultimate test—a face-off with the black sea bass predator. The sea bass could tell which squid were injured and went after those two groups right away, opting for the easier kill instead of targeting the non-injured group.
However, the pain that injured squid felt ultimately helped them survive, with 45% of the experimental group surviving attacks from the black sea bass while less than 25% of the group that received local anesthetic survived.
When in defense mode, squid tend to move in a certain sequence designed to protect them against predators. The squid that felt pain were more likely to sense the impending danger posed by the sea bass and responded by escalating their defensive postures. In contrast, the uninjured squid and those who received local anesthetic did not identify the same level of danger, and in turn, their defense mechanisms were lowered.
Watching the defensive sequence gave researchers a way to easily compare the way injured and non-injured squid assessed dangerous situations, scientists say.
Researchers concluded that feeling pain—or detecting negative stimuli—made the squid extra alert, giving them the push needed to fend off an attack and survive. This is in contrast to other theories of pain that posit the changes resulting from discomfort are negative and not beneficial to continued survival, researchers say.
Do fish feel pain? Some researchers say no.
Although the research on squid was consistent with the idea that squid feel pain, that fact in itself is very much in debate. Scientists aren’t sure whether fish and other sea creatures feel pain the way humans do. “The
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