Octopuses have a “favorite arm” they use to grab their prey

Forget about being right-handed or left-handed! Octopuses have a favorite arm they use to catch prey, study finds

  • Researchers have recorded California two-spotted octopuses attacking a variety of prey
  • They found that octopuses choose to use their second arm every time
  • But their attack strategy varied depending on the type of prey
  • The results could be used to develop an underwater vehicle or a soft robot

Whether playing tennis or writing an essay, most people have a favorite hand.

Now, a study has shown that despite choosing eight arms, octopuses also have preferred appendages.

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

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

“If we can learn lessons from octopuses, then we can apply them to creating an underwater vehicle or soft robot application,” said study author Dr Trevor Wardill.

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

California two-spotted octopus

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

The species can be identified by the circular blue eye patches on either side of its head.

Bimacs typically live for about two years.

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

Source: Animalia

When moving on the seabed or in the water, octopuses take advantage of their eight arms.

“Normally when you look at an octopus for a short time, nothing is reproducible,” Dr Wardill said.

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

In their new study, the team sought to understand if octopuses use their arms randomly when hunting, or if they have a preference.

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 ornamental Spongebob ‘dens’, with one eye facing out.

As the researchers dropped different types of prey into the tank, they recorded the octopus’ reactions.

Regardless of the type of prey that passed, each octopus attacked using the middle second arm.

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 called "bimac"is a species of octopus native to many parts of the Pacific Ocean, including coastal California

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

When it was a crab, the octopus would pounce on the prey with a “feline movement”.

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

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

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

Flavie Bidel, the lead author of the study, said: “Octopuses are extremely strong.

“For them, grabbing and opening a door is trivial, given their dexterity.”

LEFT-HANDED MYTHS

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

“In the Middle Ages, left-handed writers were thought to be possessed by the devil, generating 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 idle, weak or useless. The French word for gauche, gauche, also means awkward 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 US presidents were left-handed.

Professor Goodman suggests that what he considers a clear cognitive deficit is due to the wiring of the brain.

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

Some scientists believe that the choice to use the left hand rather than 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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