Octopus

Octopus Overview
The octopus is an eight-armed cephalopod, otherwise known as a member of the mollusk class, distinguished by its bilateral symmetry and prominent head. In sum scientists know of about 300 species of octopuses (or octopi if you prefer), approximately one-third of known cephalopod species.

Unlike squid or cuttlefish, which have some internal skeletal structure, and different from other ocean creatures that have a protective exoskeleton, the only hard part of an octopus’ body is its beak, about the size of a parrot’s and used to nip at small crabs and crustaceans, two of the octopus’ favorite meals. Having a body that’s almost entirely soft enables the octopus to navigate the tightest of squeezes between rocks and along coral reefs when eluding predators such as the lionfish, sea snakes and eels.

The life expectancy of an octopus is relatively short, ranging between as little as six months and as much as four or five years, depending on conditions. Despite this octopuses are considered to be highly intelligent, the most intelligent of the invertebrates, according to many marine biologists. Experiments have shown the octopus to possess both short- and long-term memory. It’s also suspected that much of an octopus’ behavior is non-instinctual but rather learned from its environment, as juvenile octopuses have little contact with their parents.

Octopus Anatomy
An octopus has eight arms that have suction cups all over them. They will use these arms, many at the same time, to crawl along reefs. Also, the octopus can swim by means of water jet propulsion.

Octopuses have three hearts, two to pump blood to its gills and one to pump blood throughout the rest of its body. Because of the way their bodies transport oxygen within the blood – a method called hemocyanin oxygen transportation – their blood is blue.

Though octopuses seem to be color blind, they seem to be able to differentiate between light and dark. Their eyesight underwater is quite keen, and they have a built-in response that ensures their slit-shaped pupils stay horizontal.

Octopus Reproduction
When the time comes for octopuses to mate, the male uses one of its eight arms, known as a hectocotylus, to insert sperm packets, called spermatophores, into the female’s mantle cavity. Within a few months of mating, the male dies leaving the female to care for her eggs.

Depending on the species, a female can house sperm inside her for weeks until her eggs are mature. At that time a female will lay as many as 200,000 eggs by stringing them from the ceiling of her lair or individually on the ocean floor where she will then defend them from predators. The female also pushes water currents over her eggs to ensure they receive enough oxygen. But in making all this effort to protect her eggs, the female often goes without food for the entire month-long process, which will lead to her death around the time her eggs hatch. The octopus doesn’t actually die of starvation, though. It dies of endocrine secretions from two optic glands. If these gland were surgically removed the octopus would live a few more months before eventually dying of starvation.

Octopus Diet
An octopus’ diet hinges on its life stage. Larval octopi feed on smaller bits such as plankton, larval crabs and starfish, and other small crustaceans called copepods. As they grow bigger, so does their prey, though they generally fancy reef crabs.

Octopus Threats
As residents of coral reefs, one of the chief threats to octopuses is habitat destruction. The octopus is also preyed upon by other animals that are higher up on the foodchain, such as sharks and lionfish as well as eels.

To protect itself the octopus possesses a series of defense mechanisms. Its ability to secrete ink clouds helps the octopus evade predators that depend on a sense of smell to catch their prey (such as the shark). Also, some species of octopus have the ability to camouflage their bodies, whether blending in with their surroundings or shifting shapes to look like more dangerous animals. Finally, the octopus has autotomising limbs, or the ability to detach its arms if necessary much like a lizard will detach its tail. These mechanisms each contribute toward the octopus’ survival.