Octopuses are famous for their eight arms, which leverage them when moving through the water and hunting. Their movements look awkward and seemingly unplanned sometimes; others describe them as resembling creatures out of this world.
Now, biologists investigated the hunting practices of octopuses and found that these cephalopods prefer certain arms over others they use while hunting rather than using them equally, Science Alert reported. They noticed that each octopus uses the second arm from the middle no matter the type of prey presented to them.
What Researchers Found
Assistant professor Trevor Wardill from the College of Biological Sciences, who has been studying octopuses and cephalopods for years, said that the findings are a bit unusual given that octopuses seem always to squirm around.
In their study, titled "Octopus bimaculoides' arm recruitment and use during visually evoked prey capture," published in Current Biology, researchers studied the California two-spot octopus, which lives up to two years and grows as big as tennis balls. They aim to get a better understanding of how octopuses use their arms that they can use in developing future soft robots.
The team numbered each octopus arm, starting at the center. As seen in the video, they dropped different types of prey, like crabs and shrimps, into the tanks and recorded their behavior. The octopuses are seen hiding in ornamental Spngebob dens with one eye sticking out and then lunging for their food.
At the end of the experiment, they found that octopuses used the arm on the same side as their viewing eye. More so, they attack using their second arm from the middle regardless of their prey.
Each type of prey required different tactics since crabs move slower than shrimps, which can flick their tails to escape their predator quickly. Octopuses pounce on crabs with a cat-like movement with their second arm as the lead, while they are more careful in poking shrimps using their second arm. They only use arms one and three to secure their prey.
Octopus Arms are Mirrored
The next step is for biologists to analyze how the octopus's central nervous system is involved in recruiting other arms to capture prey. According to Cosmos, octopus arms are unlike human handedness because each arm is mostly mirrored and "functionally equivalent" despite the slight bias.
"To some extent, this organization can be seen as the Hominidae fingers where each digit of the left and the right hand are the mirror of each other and skilled for individuated finger movements," researchers wrote.
Wardill and his team suggest that more than the interest in learning about the behavior of octopuses, the understanding of how their arms work could allow for the development of better-designed robots.
He noted that their experiment showcases octopuses' strength and their dexterity in grasping their prey, which can be applied to making underwater vehicles or soft robots.
Watch the video below to see how the experiment went:
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