Octopus is a cephalopod mollusc that is part of the Octopoda order. The octopuses have two eyes and four pairs of arms.
Compared to the other cephalopods, the octopus arms are symmetrically arranged bilaterally.
His mouth is in the middle of the tentacles. Their body does not have the bone structure, which allows them to pass through tight places. Octopus are by far the most intelligent invertebrate animals.
They can be found in various parts of the ocean, including coral reefs, algae or ocean bottom.
They have many strategies to defend themselves against predators: spreading in-water, camouflage, swim pretty fast, and the ability to hide.
All octopuses are venomous, but only one species is dangerous for humans: blue-ringed octopus.
There are around 300 recognized octopus species, that is one third of the total number of cephalopods.
The octopus feeds on small octopus, shellfish, snails, fish, turtles, crustaceans (eg shrimps) and other octopuses.
They catch the prey with their arms and kill it by paralyzing it with the poison then eating their flesh. Caracatites usually hunt at night.
Only the blue-ringed octopus has a poison so strong to kill a man. Some bigger species hunt birds, sharks, and other animals.
Octopus is well-known by the eight arms that have suckers (most species). They are used for locomotion and feeding.
Unlike other cephalopods, octopuses have soft meat throughout the body and not the skeleton. They do not have external protection such as carapace, scales, spikes, etc. At the bottom one can see a beak similar to a parrot, the only rigid part of the body.
The lack of rigid masses allows them to slip through very narrow slots or among stones, which is very useful when they run from predators.
They live in deep-sea habitats, as well as in coral reefs and smaller waters.
The octopus have three hearts, two that pump blood through each of the two gills and one that pumps blood into the body. The octopus blood is rich in copper and this helps to transport oxygen.
Although copper is normally more inefficient than iron, in low temperature conditions, copper-based oxygenation (if it is so) is more efficient.
Like mollusks, octopuses have gills that are divided and vascularized on the inside of the body’s outer surface.
These animals have an extremely complex nervous system and only a part is located in the brain. Two-thirds of the neurons are in his arms.
Tentacles present a series of complex reflexes that move independently making no connection to the brain. Unlike vertebrates, it is believed that locomotor movement is not commanded by the brain.
Common octopuses are between 15 and 75kg in weight with arm lengths over 4m. There are also record specimens, there are records with a specimen weighing 272kg and the tentacle of 9m.
The octopus have a short period of life. Some live less than 6 months, and larger species, such as the Pacific Giant’s octopus, can live up to 5 years.
Reproduction is fatal, males live a few months after mating, and females shortly after eggs come out. These (females) do not feed for one month, from the laying of the eggs to the babies.
Endocrine secretions from the two glands are the cause of death, but even if they were surgically removed, the octopus would die because it would not be able to feed and starve.
Octopuses are very intelligent animals, probably the most intelligent invertebrates. Biologists have made a labyrinth for capacity observation, and experiments have demonstrated that they can store information both in the short and long term.
A dilemma has remained about octopus babies, although they spend little time with their parents and do not seem to learn much, they have a wealthy knowledge base.
Octopus is the only invertebrate that has proven it can use tools. Several species, such as the Mimic octopus, have a defense system in addition to the rest of the octopuses: they take the form of other more dangerous marine mammals such as sea lions, sea serpents, angels. They have an excellent sense of touch.
The best defense of an octopus is to hide, not be seen or detected. If the first defenses were wrong, it has a few “probably in the sleeve”.
As alternative defense methods, we can distinguish ink sacks, camouflage or self-sharpening. Like ferns or lizards also octopuses can leave the predator a more or less tentacle.
Most octopuses remove a large black cloud of ink that helps them get rid of the predator. This ink has melanin as the main agent, the same substance that gives color to the hair or human skin.
Camouflage is aided by skin cells that can change apparent color or opacity. Skin pigments contain colors like yellow, orange, red, brown, black, etc. Some octopuses have two or four pigments, others have reflective cells.
Camouflage can be used for communication with other octopuses or warning.
During reproduction, the male uses a tentacle called hectocotylus to insert the semen into the cavity of the female mantle. Hectocotylus is usually the third right arm.
Males die a few months after mating. In some species, if necessary, the female can hold the semen within four weeks until eggs develop.
After being fertilized, the female deposits approximately 200,000 eggs. After laying the eggs are constantly guarded by predators. Periodically it leaves a wave of water to oxygenate the eggs.
The female has not been hunting for nearly a month and in extreme cases it is eating its tentacles. After this period, when the babies start to get out of the egg, she leaves and is vulnerable to the attacks.