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Specifically for the New York Times Infobae.
In its small glass aquarium, an octopus curls up serenely in its hiding place.
Then a crab falls into the tank.
The octopus lunges at the crab (not so much like a finely tuned killing machine, but like a little kid who’s just seen a cracker) and envelops its prey in a cloud of sucker arms and legs.
Still, there is order in this limb chaos, according to an article published Tuesday in the journal Current Biology. Scientists who watched the octopus hunt found that this animal almost always uses its second arm, counting from the middle, to grab prey, and when it needs reinforcement, it’s the arms that come to that second arm are closest to the limb that come into action. The researchers also discovered that they hunt each prey using a different tactic: in the crabs, they make a move scientists call “parachutes,” while in the shrimp, which are shyer and more sensitive to sudden movements, they use a stealthy limb to catch . . .
It seems that squid hunt by instinct rather than sight. They are often seen searching for crabs and other prey rather than simply chasing after them.
“They roam the reef and speculate by sticking their arms through the holes,” explains Trevor Wardill, a professor of ecology at the University of Minnesota who studies the vision of squid and other cephalopods and is the author of the new paper.
However, sometimes the octopuses will see a tasty creature and grab it. Wardill and Flavie Bidel, a postdoc in his lab, were curious about how this lesser-studied form of hunting works, so they set up high-speed cameras around octopus tanks and dropped live crabs and shrimp down a chute to see what they were doing. the cephalopods.
After reviewing hundreds of videos of octopuses in action, they identified a series of movements that are repeated over and over again. There’s the parachute, for example, in which the octopus swoops down, expands the membranes between its limbs to accommodate prey, and uses them to carry its dinner to its mouth. There is also the “snap trap”, in which two pairs of arms stretch around the prey like pincers.
There was also a weird little maneuver the squid performed when they encountered a shrimp that scientists dubbed “the wave.”
When a shrimp senses movement in the water, it flicks its tail and sprints away, a move Wardill calls “ballistic, let’s get out of here.” In the videos, the octopuses often stretch out an arm in front of them, waving it gently before wrapping it tightly around the shrimp’s antennae and plunging in to the hunt. He suspects that this undulating motion could be a way of bypassing the shrimp’s sensors, meaning the crustacean could feel as if an alga was waving nearby, allowing the octopus to disguise its presence.
The researchers were also interested in the fact that squid tend to use the second arm off the midline of their body, on the side facing the prey, to guide an attack.
“There has to be a hierarchy in the octopus brain,” a way to control the order in which the limbs move, Wardill said.
Octopus limbs “are very flexible at a really amazing level,” he added, being able to take on nearly infinite configurations and shapes to a degree that may seem random.
However, the study suggests that each limb likely has a specific function during a sighting session. Perhaps all this maelstrom hides a carefully choreographed reaction from the average viewer not carrying a high-speed camera.
To understand what’s happening in the octopus’ brain and limbs, the team wants to be able to record what’s happening in the animal’s nervous system as it goes into action. Does the brain recruit guns in specific groups or in a specific order? Does the octopus react differently in low light?
For Wardill, Bidel and their colleagues, the answers lie further down the line, beyond experiments that see countless squid dancing under a shower of snacks.