If Your Hands Could Smell, You’d Be an Octopus | Deep Look

Those hundreds of powerful suckers on octopus arms do more than just stick. They actually smell and taste. This contributes to a massive amount of information for the octopus’s brain to process, so octopuses depend on their eight arms for help. (And no, it's not 'octopi.')

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Everyone knows that an octopus has eight arms. And similar to our arms it uses them to grab things and move around. But that’s where the similarities end. Hundreds of suckers on each octopus arm give them abilities people can only dream about.

“The suckers are hands that also smell and taste,” said Rich Ross, senior biologist and octopus aquarist at the California Academy of Sciences.

Suckers are “very similar to our taste buds, from what little we know about them,” said University of North Carolina, Chapel Hill, cephalopod biologist William Kier.

If these tasting, smelling suckers make you think of a human hand with a tongue and a nose stuck to it, that’s a good start. It all stems from the unique challenges an octopus faces as a result of having a flexible, soft body.

“This animal has no protection and is a wonderful meal because it’s all muscle,” said Kier.

So the octopus has adapted over time. It has about 500 million neurons (dogs have around 600 million), the cells that allow it to process and communicate information. And these neurons are distributed to make the most of its eight arms. An octopus’ central brain – located between its eyes – doesn’t control its every move. Instead, two thirds of the animal’s neurons are in its arms.
“It’s more efficient to put the nervous cells in the arm,” said neurobiologist Binyamin Hochner, of Hebrew University, in Jerusalem. “The arm is a brain of its own.”

This enables octopus arms to operate somewhat independently from the animal’s central brain. The central brain tells the arms in what direction and how fast to move, but the instructions on how to reach are embedded in each arm.

Octopuses have also evolved mechanisms that allow their muscles to move without the use of a skeleton. This same muscle arrangement enables elephant trunks and mammals’ tongues to unfurl.

“The arrangement of the muscle in your tongue is similar to the arrangement in the octopus arm,” said Kier.

In an octopus arm, muscles are arranged in different directions. When one octopus muscle contracts, it’s able to stretch out again because other muscles oriented in a different direction offer resistance – just as the bones in vertebrate bodies do. This skeleton of muscle, called a muscular hydrostat, is how an octopus gets its suckers to attach to different surfaces.

--- How many suction cups does an octopus have on each arm?

It depends on the species. Giant Pacific octopuses have up to 240 suckers on each arm.

--- Do octopuses have arms or tentacles?

Octopuses have arms, not tentacles. “The term ‘tentacle’ is used for lots of fleshy protuberances in invertebrates,” said Kier. “It just happens that the eight in octopuses are called arms.”

--- Can octopuses regrow a severed arm?

Yes!

---+ Read the entire article on KQED Science:

https://ww2.kqed.org/science/2....017/02/14/if-your-ha

---+ For more information:

The octopus research group at the Hebrew University of Jerusalem: https://www.youtube.com/watch?v=gN81dtxilhE

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https://www.youtube.com/watch?v=0wtLrlIKvJE

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