Wednesday, January 30, 2013

Zoo Presentation Part 2: The Giant Pacific Octopus

Yesterday I posted about the black-tailed prairie dog, the first of three animals I have been assigned for a "mock tour" this coming Friday. The second animal, the giant Pacific octopus, is the subject of today's piece. Hope you like it!

Giant Pacific octopus

Has anyone ever heard of Harry Houdini? Why was he famous? Harry Houdini was a man who lived about 100 years ago and he was an “Escape Artist”. People used to pay to see him get out of very tight spots seemingly like magic. But if Harry Houdini had been an octopus, it might not have seemed so magical!

This is a giant Pacific octopus. It is an invertebrate; does everyone know what that means? Because it has no bony skeleton or backbone it can squeeze its body through unbelievably small holes; here is something to look at we call an “Octopus Escape Route”—please pass it around. The octopus in this tank can fit through that hole in the plastic if it really needed to! Underneath the octopus where all 8 arms meet you will find its mouth. Inside that mouth is the octopus’ beak, shaped a bit like a parrot’s beak, which is made of keratin—the same substance your fingernails are made out of. That is the hardest part of the octopus’ whole body, so it can squeeze through any opening larger than its beak. Now, I mentioned the octopus’ arms: that’s what they are called, not legs or tentacles. Each arm has about 280 suckers in two rows and these contain chemical receptors which the octopus uses for touch and taste.

Just chillin' on the ocean floor
This species lives in the temperate waters of the continental shelf of the North Pacific ocean from Southern California all the way up to Alaska and across to Japan. They are found on the ocean floor from as shallow as the low tide line to as deep as 300 m or more. They spend their time in small caves or cracks to hide from predators such as sea otters and sperm whales. They very seldom leave these hiding places; if they do, it’s generally at dawn or dusk to hunt—which means they are “crepuscular”—and when they catch some prey they drag it back to their nests to eat. They seem to prefer to be an “ambush hunter”, waiting for lunch to just swim past them and then they reach a long arm out and snatch it up.

Amazing camouflage
They can defend against predators in many ways. First of all, they are “masters of disguise”. They have special pigment cells in their skin called “chromatophores” which they use to change colour rapidly to blend in with their surroundings, from a very light grey to a bright red. They have tiny muscles which will pull different coloured pigmentation sacs to the surface—yellow, red or brown; these tiny muscles can also change the texture of their skin from smooth to rough-looking or even rippled to look like the water or rocks around them.

Siphon is on the left; mouth and receding beak at right
If a predator sees through this disguise and discovers them, they can get away very quickly. Although they usually move around by using their arms to crawl they do have an emergency method of transportation. Underneath the octopus, next to its mouth and beak, there is a tube called a “siphon” which they use to expel water that has passed over their gills. They can shoot water out at a very high rate of speed and use this to propel themselves forward on a kind of “jet stream” through the water. But they can shoot something else out of this siphon, too. Can you guess what that is? Ink! They can shoot out a dark, inky substance, sometimes mixed with saliva to thicken it, which confuses their predators who will sometimes mistake the ink cloud for the octopus itself, while it makes it getaway through a tiny crack in its surroundings.

Octopuses [(not “octopi”; the root of their name is Greek and the “proper” plural would be “octopodes”, but we don’t use it)] are also very intelligent, which is why you can see toys in this tank. They can work out mazes, they have excellent long-term memory and recollection skills and they can figure out how to get into jars with the lids screwed on tightly. Because they spend much of their time alone in one place they have a chance to play or work out puzzles on their own. This intelligence is another defense mechanism: it allows them the chance to outwit many of their more simple-minded predators. 

The giant Pacific octopus does not appear to be endangered right now; however, if we continue to pollute the oceans that could change down the road. Ironically, though, some of the objects humans have polluted the oceans with—such as barrels, tires or even shipwrecks—provide homes and hiding places for the octopus once they have settled onto the ocean floor.

The last two animals we have visited live on land and in the ocean. The next animal also has a beak but prefers to spend its time in the air or high above the ground in a tree.

And off we go to the spectacled owl....tomorrow's subject!

Incidentally, there is a pretty cool video of an octopus' beak and siphon at the Bio Geo Nerd blogsite. Check it out if you get a chance—the video is very near the bottom of the page but some of the pictures are pretty awesome as well.

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