Wednesday, February 29, 2012

Is that an Octopus Walking?


Like a sea monster, the octopus (Octopus aculeatus) walks along the benthic floor while maintaining its camouflage as a piece of algae.  This specimen was captured, along Australia's Great Barrier Reef, and was used in a study carried out at Berkeley.

Could it be possible that octopuses can stroll around on two arms?  An octopus has eight arms total and recent research done at Berkeley has shown that octopuses can use two of those eight arms to run across the ocean floor as a adaption to predation.  Two species of tropical octopuses have developed this trick where they pick up six of their legs and walk or run backwards on two of them to easily escape predators.    

The first report of bipedal behavior in octopuses, was written by University of California, Berkeley, researchers, and will be published in the March 25th issue of Science.

In Indonesia, an example of bipedal movement was found in the coconut octopus, commonly referred to as this because it looks like a coconut.  The coconut octopus can be found tiptoeing along the ocean bottom having six of its arms wrapped around its body, while two are touching the ground.  The octopus is able to use the outer halves of their two back arms like tank treads when walking along.  They alternately lay down a sucker edge, located on their arms, and roll it along the ground to propel themselves forward.

The coconut octopus is found to live on sandy bottoms in water 20-30 meters deep.  They live among sunken coconuts and sometimes even hide in the shells of the coconuts to protect its self from predators.

The other octopus that was studied in the laboratory was able to propel itself backwards.  A graduate student from the University timed the two octopuses to see which was more adapted to this new trick that has evolved.  The coconut octopus moved forward at a rate of two and a half inches per second, while the other octopus moved backwards at five and a half inches per second.  These speeds are faster than they can crawl around, but slower then when they swim (jet) around.

video
The Indonesian Octopus, Octopus marginatus, scoots along the ocean floor using the tips of its arms and their suckers.

The other type of octopus that can camouflage itself as algae in tropical waters looks like a sea monster walking along the sea floor with two legs, just as the coconut octopus.  This octopus is the one at the beginning of the post, known as Octopus aculeatus.


 Octopus (abdopus) aculeatus, was found to have a head the size of a walnut and it inhabits intertidal zones, with sandy bottoms, living among grasses and hiding out in tide-pools or burrying itself in the sand at low tide so it does not dry out and get stuck on shore.  To camouflage itself, it has been seen to coil its front (2) arms and raise them in a pose to resemble algae.

The researchers at Berkeley believe that the bipedal walking strategy evolved in these two octopuses to backpedal away from predators while remaining camouflaged.  Octopuses can camouflage themselves by changing their color and shape.  Normally, when octopuses are startled they cannot move away and stay camouflaged at the same time, but with this walking behavior they can do both at the same time.

The octopuses can change shape readily because they are basically a water-filled balloon, but their fluid is contained within muscles cells rather than an open cavity.  Octopuses keep their shape due to hydrostatic pressure (hydrostatic skeleton or hydrostat).  They do not contain an external or internal skeleton, that is what the pressure is for.  For movement of octopuses they normally push and pull their suckers on their eight arms or jet backwards through the water (jet propulsion).  These movements are done through the muscles that squeeze and bend the fluid filled arms and body.

In Conclusion:

The two octopuses that are found to walk along the bottom of the sea floor and their ability to camouflage relates to the idea of predation covered in class.  This new evolved trick, can help the octopuses get away from the predators, while still being camouflaged.  These adaptions can help the octopuses to survive and this can lead to zonation and other effects in the food chain and water column.





2 comments:

  1. Wow that is really cool! I had no idea that they could change shape. That just seems like a fascinating way to adapt to camouflage themselves. The video shows the unique ways these animals have developed to survive. I found this interesting.

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  2. Pretty amazing that these animals has incorporated this bipedal behavior into its escape strategy rather than just swimming away. But I suppose that the action of swimming would decrease the effectiveness of the camouflage.

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