ZOO-ology column: Ocean Jet Setters
By Judie Farnsworth
July 22, 2012 at 2:22 a.m.
Describe a mollusk. The first thought is often shell, then clam, oyster or snail.
These are three of many thousands of such invertebrate creatures. But, not all mollusks have shells.
How about the most intelligent, jet propelled, master of disguise - sometimes called an inkfish? Ah-ha, octopuses (an accepted plural).
Simply put, there are many octopus species. Some are deep-sea dwellers and others, which are more common, are bottom dwellers. All live in the oceans of the world. They may dig under rocks and find crevices on the ocean floor. Their boneless, flexible bodies allow them to crawl into very tiny spaces.
Studies show that octopuses have learning abilities, long and short-term memory and can distinguish between shapes and patterns. They display problem solving capabilities rather than using instincts alone. Their intelligence and flexibility make these escape artists hard to keep as pets.
They're strong for their size and have been known to board fishing boats where they open and raid holds containing crabs. They even kill some sharks.
They may carry and stash a few clams so when they get the munchies, they need only to reach out and, voila.
A clam shell is no problem for the hard, parrot-like beak of the octopus and there's a toothed, rasping tongue inside the beak.
They've learned to use discarded shells as protection and can be seen with shells in tow.
The octopus is amazingly quick and effective at camouflaging. It changes its color using pigment cells. Specialized muscles can even alter the appearance of its texture - spiky, bumpy or even rough, like a rock.
Hiding may be either for safety or ambush-style hunting.
When super speed is needed, a muscular tube called a siphon is used. Water is sucked into the body then blasted out through the siphon for an octopus in a hurry.
Most can eject a thick inky substance that helps with defense, which is held in a special sac that contains melanin, a substance that also colors our skin and hair. In some species, it has a numbing effect and may disturb a predator's sense of smell.
There are three hearts pumping blood through the body and all those arms. Two pump through the two gills and one pumps blood through the rest of the body.
Octopuses are deaf, but they have two rotating eyes and excellent sight. They have horizontal pupils and polarized vision, which lets them see even almost invisible jellyfish.
The term arm, rather than tentacle, is correct. Tentacles are longer with suckers only at the tips. Arms may have hundreds of suckers with sensory receptors at the bottom, allowing a wonderful sense of touch.
An octopus' eight arms seem to have a mind of their own and, with no bones or joints, are super flexible. The brain sends an impulse to move the arms, but the actual type of movement appears to be programmed in the arms themselves.
Scientists have yet to figure how they are controlled, and are used to crawl, manipulate and carry.
The octopus can shed an arm to distract a predator and it will grow back in time. They're truly fascinating creatures.
I invite you to look on the Internet earthjustice.org for a fascinating video of an octopus digging up and carrying a large coconut shell.
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.