[貼圖] Shape-Shifting Cuttlefish Can Mimic Pictures

本帖最後由 netaccess 於 2011-6-24 08:47 AM 編輯

No One Here But Us Plants
During  recent research into how cuttlefish adopt camouflage positions, a  common cuttlefish (left) raises two of its eight arms in apparent  mimicry of artificial algae placed in its tank. The animal reacted  similarly when shown a photo of green algae, said biologist Roger Hanlon.
It's  been known that many cuttlefish—and their squid and octopus  cousins—adjust their postures and rapidly change color to resemble  nearby objects, a strategy to evade predators.
But  the recent lab experiments are the first to confirm that cuttlefish use  visual information to determine those gestures, according to Hanlon, of  the Marine Biological Laboratory in Woods Hole, Massachusetts.
"Camouflage  is one of the least studied subjects in biology. It would be nice if  our paper encourages folks to look at this behavior more carefully in  other animals," said Hanlon

Spot the Squid
Shown in the wild, a Caribbean reef squid—a cuttlefish cousin—raises its arms straight up, parallel to soft coral branches.
Some  shape-shifting cephalopods—squid, octopuses, and cuttlefish—can hold  their positions for as long as 40 minutes, Hanlon said. "It's not a  temporary thing, when they want to go in there and look like a piece of  the swaying soft coral."
In  the case of Caribbean reef squid, long dark stripes add to the  disguise. "It's a very elegant and sophisticated pattern," said Hanlon,  whose research has received funding from the National Geographic  Society's Committee for Research and Exploration. (The Society owns National Geographic News.)

Cuttlefish Falls in Line
A common cuttlefish lifts its arms upright (left) and at an angle to match stripes in an aquarium.
The  use of two-dimensional patterns allowed the researchers to precisely  measure how well the arm positions corresponded to the backdrops—and to  rule out the possibility that the animals were basing their  configurations on touch, according to study co-author Hanlon.
And  because the experiments were done in controlled aquariums, the  researchers could be sure the cuttlefish weren't reacting to chemical  cues.
Reaching  about 17 inches (45 centimeters) long, the common cuttlefish changes  its color and skin texture to evade predators, including marine mammals,  fish, and seabirds.
"They  have an enormous variety of predators, some of which have marvelously  good visual capabilities," Hanlon said. "That's why the [cuttlefish]  camouflage has to be so good."

Touching Down
A wild common cuttlefish in Turkey points its arms into the sand, mirroring algae branches nearby.
Found  along shorelines in most parts of the world, but not in the Americas,  these cephalopods can assume camouflage positions within seconds of  entering a new environment when they sense danger is near.

Undercover Cuttlefish
Nestled  amid algae stalks, a wild Australian giant cuttlefish raises its arms  to blend in with its surroundings. "It’s very hard to tell that's a  cuttlefish," Hanlon said.
The world's largest cuttlefish species, the Australian giant grows to as long as about a yard (a meter).

Make Like An Algae
Next to a tall piece of algae, a common cuttlefish in the wild attempts to hide by lifting its arms.
The common cuttlefish hunts the oceans for crustaceans and fish and uses ink in its skin to change color rapidly.

The Squid and the Sea Fan
Continuously  jetting water out its back end to stay afloat, a wild Caribbean reef  squid appears to be an extension of a sea fan.
Up close, the creature catches the eye, but "in the full-frame picture, that animal is very hard to see," Hanlon said.

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