Octopus lives in many areas of the ocean, including coral reefs, pelagic zone and the seabed, some also live in the intertidal zone or the deep sea zone, although purely marine animals, but the octopus in the land but also can maintain a considerable flexibility of movement ability. Most octopuses have a short lifespan, growing rapidly, maturing, then mating and dying. Male octopuses mate using a special tentacle called a „chemostat,“ which they use to inject sperm directly into the female’s coat membrane. After mating, the male octopus enters a senescent phase and dies quickly, and the female octopus dies quickly after her fertilized eggs hatch. Octopuses‘ defenses against threats include squirting ink, changing color to camouflage or deterring enemies, and they can use water spray to achieve a quick escape. All octopuses have venom, but only the venom of the blue-ringed octopus genus is dangerous to humans.
The octopus appears in many myths, legends, literature and works of art, such as the Norwegian Sea Monster in Norse mythology, Victor Hugo’s novel Laborers at Sea, and the Japanese erotic painting The Octopus and the Sea Maiden, to name a few. Octopuses are used as food in many parts of the world, such as Korea, Taiwan, Japan, the eastern seaboard of China, throughout Southeast Asia, southern Europe and the east coast of the Americas and the Mediterranean Sea.
The order Octopus contains about 300 known species, and historically it was divided into two suborders: the wingless and the winged. However, recent studies have concluded that the winged suborder is simply a more primitive group of species and is not a separate evolutionary branch. The finless suborder makes up the majority of octopus species, and in contrast to the finned suborder, they lack the two fins used for propulsion, and their body shells have either become stiletto tubes or have disappeared altogether!
Cephalopods evolved from monoplankton during the Cambrian period, about 530 million years ago. During the Devonian period, about 416 million years ago, the subclass Octopoda separated from the subclass Nautilus. During the Permian Period about 216 million years ago, the shells of the subclass Octopoda (which includes octopuses and squids) gradually shifted to the inside of the body, and this led to the classification of the octocarpal and decacarpal subclasses. [5] The modern octopus evolved from the Jurassic superfamily Minster Octopoda. Early octopuses probably lived in shallow marine environments, inhabiting the benthic biota to the benthic zone. Much of the octopus’s body is composed of soft tissue, so the fossil record is relatively sparse. As soft-bodied cephalopods, they lack the hard outer shells of their relatives (e.g., nautilus subclass and chrysomelids). They had eight limbs like other Octopoda, but lacked specialized feeding limbs called tentacles (the scientific name for which is tentacle; octopus tentacles would be accurately called tentacular arms), which were thinner, longer, and had suckers attached only to their ends.