Anchorage Daily News

Often-misunderstood octopus generates myths, amazing facts


By Doug O'harra
Anchorage Daily News


(Published July 15, 2001)

With writhing arms and an uncanny knack for figuring things out, the octopus is one of the strangest animals in the sea -- the unblinking savant of an extended family that includes clams. Their alien appearance and mute squishiness unnerves some people, offering raw material for legend and nightmare.

Stories inspired by octopuses (and the 700 other species in the cephalopod class of squids, nautilus and cuttlefish) span the globe. They range from classic yarns of gigantic devilfish wrestling ships to smithereens to a cautionary fable about how a slithering army of octopuses once attacked a Tlingit village that had shown disrespect.

Cephalopod biologists, "a playful group of people," according to David Scheel, love to share sea-monster stories.

Such stories often have a kernel of truth. For instance, Scheel has come on scientific journals that describe seasons when huge unexplained concentrations of octopuses infested certain European shorelines. So maybe something natural really did happen once in Southeast Alaska.

"It may be that the conditions were really good the year the octopuses attacked the village," Scheel said.

The animals are no less remarkable in real life. When seen by divers or held captive in aquariums, octopuses seem to exhibit curiosity and intelligence normally associated with vertebrates.

Ulu, a male octopus that Scheel helped care for in Cordova, lived at the Seward Sea Life Center, where it was able to open peanut butter jars and scramble from its tank. To snatch quick snacks, octopuses have been known to climb aboard fishing boats and open fish holds full of crabs.

SHY, SECRETIVE

But the species is neither trickster nor leviathan. The giant Pacific octopus -- the largest known variety that can exceed 20 feet from arm tip to arm tip -- is a shy, secretive creature caught between competing demands.

To satisfy an enormous appetite -- an octopus can increase its body weight 2 percent a day -- octopuses must forage on the dim sea floor. But the formidable crustacean-slayer must avoid a host of larger, faster and toothier enemies. As a result, the species has evolved an astonishing array of tricks.

When confronted with danger, they can alter their skin pigment to blend into the background, or squirt a cloud of "ink" to distract predators. Octopuses can shoot into motion by expelling a jet of water. Arms bitten or torn off can be regrown.

If cornered, an octopus will fight back, wrapping arms around enemies, or covering them with their flexible web, the membrane between arms.

In their quest for tasty morsels or a secure den, octopuses deploy sight superior to our own. Each flexible sucker can identify a frantic kelp or helmet crab by how it tastes, then snatch it up. Octopuses, in effect, have thousands of sticky fingers on their arms, able to pass food from sucker to sucker to the hard beak in their mouth.

One octopus Scheel and Vincent captured on Green Island was clutching dozens of crabs and clams as it cruised the shore.

"It was like she had a shopping bag under her mantle," Vincent said. "She had a whole bag full of food that she was going to take back to her den."

For all their capacity, giant octopuses only live three to five years. The third right arm of males has a spoonlike tip for depositing sperm inside the mantle of females in an hours-long mating process that takes place 60 to 300 feet beneath the surface. Males are thought to live only a few months afterward. Later females will hang 20,000 to 100,000 eggs inside a den like strings of rice, tending them and blowing water across them until they hatch. Seven months in the nursery leaves the mothers so weakened that they die.

"They're like salmon," Scheel said. "They spend their energy and their resources on that breeding season, and when it's done, it's done."

Baby octopuses are thought to swim right to the surface to live as plankton, drifting helplessly on the currents for up to three months. Once they get big enough, about five grams, they drop to the sea floor, staking homes anywhere from intertidal shallows to inky depths 600 feet down. They grow fast, reaching 2 to 3 pounds within one year.

Adults often top out at 30 to 50 pounds in Alaska, rarely growing to more than 100 pounds even in the Pacific Northwest. But larger, almost mythic creatures have surfaced. One huge octopus captured off Victoria, British Columbia, in the late 1960s weighed about 156 pounds with arms that spanned 23 feet. Even larger octopuses have been reported, some exceeding 300 pounds.

Seeing such a big octopus is a thrill for most biologists.

"I have to admit it," Scheel said. "When I went down in the sub, I wanted to see the giant 600-pound octopus."

Doug O'Harra can be reached at do'harra@adn.com or 907 257-4334.





Copyright 2001 The Anchorage Daily News (www.adn.com)