Octopuses have a ‘favourite arm’ they use to grab prey

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Forget being right or left handed! Octopuses have a favorite ARM that they use to grab prey, study finds

  • Researchers recorded California two-point octopuses attacking various prey
  • They found that the octopuses chose to use their second arm every time
  • But their attack strategy varied depending on the type of prey
  • Findings can be used to develop an underwater vehicle or soft robot

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Whether it’s playing tennis or writing an essay, most people have a preferred hand.

Now, a study has shown that despite having eight arms to choose from, octopuses also have favored appendages.

Researchers at the University of Minnesota recorded octopuses attacking various prey, and found that they preferred certain weapons over others when hunting.

The team hopes the findings can be used to develop the next generation of highly manipulative soft robots.

“If we can learn from octopuses, we can apply that to creating an underwater vehicle or soft robotic application,” said Dr Trevor Wardill, an author of the study.

University of Minnesota researchers recorded octopuses attacking various prey and found that they preferred certain weapons over others when hunting

University of Minnesota researchers recorded octopuses attacking various prey and found that they preferred certain weapons over others when hunting

The California Two Spotted Octopus

The California two-spotted octopus, often referred to simply as a “bimac,” is a species of octopus native to many parts of the Pacific Ocean, including the coast of California.

You can recognize the species by the round blue eyespots on either side of its head.

Bimacs usually live to be about two years old.

They are closely related to Verrill’s two-headed octopus.

Source: Animalia

As they move across the seabed or flow through the water, octopuses use all eight of their arms.

“Normally, if you just look at an octopus, nothing is repeatable,” said Dr Wardill.

“They squirm around… and just look weird in their exploratory moves.”

In their new study, the team tried to understand whether the octopuses used their arms randomly while hunting, or whether they had a preference.

The researchers studied the California two-spotted octopus — a species that lives for about two years and can grow to the size of a tennis ball.

The octopuses were housed in a tank, where they hid in decorative SpongeBob ‘burrows’, with one eye facing out.

As the researchers dropped different types of prey into the tank, they recorded the octopuses’ responses.

No matter what kind of prey came by, each octopus attacked with the second arm from the center.

Surprisingly, however, their recordings revealed that the octopuses used different attack tactics depending on the type of prey.

The California two-spotted octopus, often simply a "bimac"is an octopus species that is native to many parts of the Pacific Ocean, including the coast of California

The California two-spotted octopus, often simply a "bimac"is an octopus species that is native to many parts of the Pacific Ocean, including the coast of California

The California two-spotted octopus, often referred to simply as a “bimac,” is an octopus species native to many parts of the Pacific Ocean, including the coast of California.

When it was a crab, the octopuses pounced on the prey with a “cat-like movement.”

But when it was a shrimp, they were slower with their approach, using their second arm to make contact with the shrimp before using the two adjacent arms to secure it.

The researchers were surprised to see that the same attack strategies were used in different octopuses, all showing a preference for their second arm.

The team now hopes to look at how neurons facilitate these arm movements.

Flavie Bidel, the study’s lead author, said: ‘Octopuses are extremely strong.

“To them it is insignificant to grab and open a door, given their dexterity.”

MYTHS ABOUT LEFT HANDED

Professor Joshua Goodman, a Harvard economist who conducted the study, said left-handedness has long been viewed with suspicion.

“During the Middle Ages, left-handed writers were thought to be possessed by the devil, which gave the modern meaning of the word sinister from sinistra, the Latin word for left,” he said.

‘The English word left itself comes from the Old English lyft, which means inactive, weak or useless. The French word for left, gauche, also means clumsy or clumsy.’

The popular perception that left-handers are more gifted came later, he said, encouraged by anecdotal evidence, including the fact that four of the last seven U.S. presidents were left-handed.

Professor Goodman suggests that what he sees as a marked cognitive deficit is due to the brain’s wiring.

The way the brain works is fundamentally linked to “hemispheric bias” – the way various functions are associated with the left or right side of the brain.

Some scientists believe that the choice to use the left hand over the right is influenced by how this hemispheric bias developed in the womb, when the basic structures of the brain were first formed.

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