Courtesy Roy Caldwell, U.C. Berkeley
Fleshy projections on the skin of the walnut-sized "algae octopus" — whose scientific name is Octopus aculeatus — allow it to camouflage itself like algae in its natural habitat.
Practically every animal that gets around on two feet has bones to help it do the job. Now scientists have discovered that, despite having no bones in their bodies, two octopus species have mastered bipedal locomotion by ambling along on two arms.
Berkeley graduate student Christine Huffard and her colleagues discovered the behavior in both species. Huffard came across one octopus walking on two arms while helping a film crew in Indonesia. The second species was discovered ambling along on two limbs in the waters off Australia.
Instead of relying on bones, the small octopuses use flexible muscles supported by the fluid inside them. And both species may be using the technique as camouflage. Octopus aculeatus holds its arms up and ends up looking like algae. Octopus marginatus tucks its arms under, which makes it look like a coconut — and coconuts are everywhere on the sea floor where it lives.
Huffard and her colleagues write about their findings in the current issue of the journal Science.
The "algae octopus" uses a rolling gait to walk backward on its ventral pair of arms. All of its other arms are raised above its head — camouflage that makes the creature look like a floating clump of algae.
The "coconut octopus" walks backwards, holding its six arms under its rounded body, which gives the animal the appearance of a coconut shell rolling along the ocean floor.
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