|31 Oct 2001 @ 10:53, by sindy|
Octopus Arms Found to Have "Minds" of Their Own
Photograph by corbisimages.com
From the way a severed octopus arm behaves during predation, scientists have suspected that it must have some kind of independent intelligence.Now researchers have discovered that octopuses do indeed have "brainy" arms.
Octopus Arms Found to Have "Minds" of Their Own
for National Geographic News
September 7, 2001
An octopus may get some mileage out of the excuse "I can't help it, my arm has a mind of its own," as it goes for an extra sea morsel—at least more than can a human who reaches too often into the cookie jar. Neither, however, can lay full blame for their greed on their appendages.
For humans, the brain inside the human skull, the same brain that sees the cookie and wants to eat it, controls the reach into the cookie jar. Octopus arms, on the other hand, really do have a mind of their own, according to research reported in the September 7 issue of Science.
The brain inside the octopus skull sees a tasty sea morsel and decides to eat it, but to get the morsel into its mouth the brain inside the skull sends a message to a mass of nerves inside the octopus arm. That mass of nerves controls the arm movement to snatch the tasty treat.
"In this hierarchical organization, the brain only has to send a command to the arm to do the action—the entire recipe of how to do it is embedded in the arm itself," said Binyamin Hochner of the Institute of Life Sciences at Hebrew University in Jerusalem, Israel, and co-author of the research.
Octopus arms, unlike human arms, are not limited in their range of motion by elbow, wrist, and shoulder joints. To accomplish goals such as reaching for a meal or swimming, however, an octopus must be able to control its eight appendages.
Trying to work out how octopuses control their flexible arms is the goal of Hochner and his colleagues' research at Hebrew University.
The researchers' observations indicate that octopuses reduce the complexity of controlling their arms by keeping their arm movements to set, stereotypical patterns. For example, the reaching movement always consists of a bend that propagates along the arm toward the tip, said Hochner.
Since octopuses always use the same kind of movement to extend their arms, Hochner and his colleagues wondered if the commands that generate the pattern are stored in the arm itself, not in the central brain. Such a mechanism would further reduce the complexity of controlling a flexible arm.
Severed Brain and Functioning Arm
To find out if octopus arms have minds of their own, the researchers cut off the nerves in an octopus arm from the other nerves in its body, including the brain. They then tickled and stimulated the skin on the arm. The arm behaved in an identical fashion to what it would in a healthy octopus.
The implication is that the brain only has to send a single move command to the arm, and the arm will do the rest.
"This work quantifies in a very nice way what we have suspected based on the large amount of nerves in the octopuses and from the behavior of severed arms during predation," said James Wood of the National Center for Cephalopods at the University of Texas in Galveston.
"Arms have a lot of autonomy and the central brain of an octopus gives high-level commands but may not be aware of the details—in other words, there is a lot of processing of information in the arms that never makes it to the brain," he added.
This research shows the mechanism by which octopuses are able to operate an arm that has a nearly infinite range of motion. This has been a long-term goal of the Israeli researchers not only because of their interest in nature, but also to learn how to produce a flexible and robust robotic arm.
"A flexible [robot] arm would not be constricted by the environment. It would be a better robot for unpredicted situations such as a natural disaster or surgery in a delicate area," said Hochner. "It would have infinitely large degrees of freedom which are not constrained by the fixed joints of other robots that are currently used."
Now that the researchers have figured out how octopuses control their flexible arms, the next challenge is to find a material that can replicate the property of an octopus arm. Currently nothing comes close, said Hochner.
In the meantime, scientists will remain awed by the intelligence of octopuses, which are thought to be the most intelligent of the invertebrates (species that have no spine).
"This [research] shows that centralized processing of all incoming information is not the only way to develop a neural network," said Wood. "Interestingly, a significant number of computer science folks take an interest in cephalopods. This gives them one more reason to do so."
Scientists reveal monster secrets
By Michael Peschardt in Sydney
One of the mythical creatures of the ocean has been found deep down in the waters off Tasmania.
The giant squid have been discovered caught in the nets of trawlers.
Sailors of centuries ago told tales of being attacked by beasts whose tentacles could rip a man apart.
Incredibly, the latest finds mean the ancient tales can no longer be dismissed as the work of superstitious scaremongerers.
David Pemberton of the Museum of Tasmania says: "I don't think it's beyond the realms of possibility.
"All the creatures we have brought up are dead, killed by the rapidly changing pressure.
"But it does make you wonder how they could have made those drawings so long ago unless they had actually seen them."
Twenty metres long
The specimens the scientists are working on are giant squid which weigh a quarter of a ton and measure twenty metres in length when fully grown.
Hardly anything is known about these creatures, whose capacity for growth is extraordinary. They begin life the size of a matchstick and grow to full size within three to four years.
Liz Turner of the Museum of Tasmania says: "There's no doubt that squid are prepared to attack the largest of prey, including sperm whales."
no storage space for giant squid
Strange and exotic creatures have been plucked out of the Tasmania waters for years, adding to the list of fishermen's tales.
But this the first time those tales are being subjected to the strictest scientific scrutiny.
Now the least of the challenges is how to store the three giant specimens which they have frozen down ready for further study.
The giant squid are not the only amazing things found in recent months. There is also a three-metre long pregnant calamari.
Liz Turner said: "So little is known about what lurks deep down below the oceans it's possible seafarers several hundred years ago knew more than we do."
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