The octopus is a Cephalopod Mollusc. Cephalopod comes from the latin for head-foot and mollusc meaning soft; so an octopus is a soft head-foot! The octopus is a rather magnificent animal. Perhaps the most defining feature of the octopus is its 8 arms. Each arm usually has a ‘suction-cup’ at the end of it. The cup is used as a means of catching pray and hanging on to various surfaces. The ‘arm’ itself is hydrostatic. This means that it contains no skeleton support and therefore moves independent of bones. A more familiar hydrostat is the human tongue.
Octopus, under stress, have been known to eat their arm as a way of surviving. This is particular true for the Giant Pacific Octopus. In order for her young to survive, the mother octopus will lay her eggs and then starve herself to death. Once the octopus eggs begin to hatch, they will then feed on the mother. In order for this to be evolutionary ‘successful’ the mother must produce an enormous amount of offspring at one time. The Giant Pacific Octopus has been recorded at laying over 50,000 young at once! If she did not lay as many offspring, then it is unlikely that many would survive to full adulthood. This parental strategy also means that octopus young must be very self-sustaining because of the lack of any parental guidance from birth.
Another somewhat bizarre feature of an octopus is that they have a beak. The beak, made of chitin, forms the only hard part of their body. It is used for digging in sediments and for breaking up parts of the food for eating. Their beak is part of what makes them a mollusc. Molluscs generally have a chitin based ‘shell’ and in the octopus this has been modified to form the beak.
Octopuses are also known for their incredible intelligence. They are thought to be the most intelligent invertebrates. Their is much debate about the total degree of intelligence that they have; but some maze experiments have shown them to have the capacity for short and long term memory. Surprisingly, most of the neurons in an octopuses’ body are not found in the ‘brain’ but are found in the 8 limbs. This means that many octopus limbs show signs of activity even if they become detached from the ‘head’. Some have been trained to distinguish between certain objects and colours and others, in the wild, have been seen to mimic other creatures of the ocean.
Octopuses have also been shown to be able to use tools. For example, the ‘Veined Octopus’ has been recorded picking up pieces of coconut shell and reusing them as a form of shelter. This type of behaviour is extremely rare in the animal kingdom; especially in aquatic life. Another example has been noted in aquariums where octopus , to find food, would leave their own enclosures and enter the tanks crabs. This type of intelligence has led to the Octopus becoming a ‘protected’ animal for animal testing. This type of protection is also given to higher primates like chimps.
Finally, octopus is often a delicacy in some parts of the world. Most notably, in Korea, live Octopuses are eaten. There have been reports of people dying of suffocation from this practice because the octopus tentacles may move about in the mouth and block the oesophagus. Other species of octopus MUST be cooked and boiled before eaten. If not then some of the ink that remains in the octopus may poison the consumer!
The plural of ‘Octopus’ is Octopuses. This may seem strange when you compare it to say Cactus/Cactii. However, another commonly used word for the plural of Octopus is Octopudes. This is the Greek plural for Octopus and is sometimes still used today.