No other animal of the sea has been so misunderstood, feared, and vilified as the lowly octopus.
The octopus is an invertebrate that belongs in the phylum Mollusca along with chitons, clams, snails, mussels, etc. It is closely related to the cuttlefish and squid. There are around 250 species of octopuses that have been described, with the giant Pacific octopus thought to be the largest species living today.
The octopus is considered to be the most intelligent of all the invertebrates. They are generally asocial with others of their kind except during mating season. The octopus has eight arms or tentacles that are covered completely with powerful suckers that harbor numerous chemoreceptors for detecting scents and chemicals in the environment. They get around using a type of jet-propulsion produced by forcing a stream of water out of a flexible, funnel-shaped siphon. It also uses this system to blow a stream of salt water at something they don't like or to get attention.
In addition, they use their tentacles for walking on the sea floor, crushing the shells of other mollusks, gathering food, and putting items into their mouths. The tentacles can be as swift as a whiplash in snaring prey and are surprising strong. The octopus has a hard beak located at the base of the tentacles that can be used to bite as well as inject a neurotoxic venom. It also has a saliva that can dissolve flesh.
Both the squid and octopus have the most complex eyes of all the invertebrates, and this eye is very similar in structure to the eyes found in vertebrates.
Most octopuses grow no larger than 3 feet across. However, some species are so tiny that as adults, they could sit on your fingernail. Record books list the largest captured octopus at 300 pounds with an arm span stretching 32 feet. However, recently larger specimens weighing more than 400 pounds have been reported.
Scientists believe that there may be much larger specimens in the depths of the vast Pacific Ocean that have not been found. There are many unsubstantiated reports by ancient seamen of encounters with huge squids and octopuses in their travels.
The giant Pacific octopus is one of the fastest growing animals on the planet. It hatches from an egg the size of a grain of rice and can grow both longer and heavier than a man in just three years. Octopuses tend to die young, and the giant Pacific octopus is probably among the longest-lived of all the species. They usually live for only about 3-4 years.