octopus

The plural is octopuses or octopi.

Octopus, also known as octopus, is a kind of marine mollusk.

Cephalopod mollusks of the class Octopoda. But strictly speaking, it only refers to octopus, which is widely distributed in shallow water.

Octopuses vary greatly in size. The smallest octopus is O. arborescens, which is about 5 cm (2 inches) long, while the largest octopus can reach 5.4 meters (18 feet) and the wrist span can reach 9 meters (30 feet). Typical octopus body is saccular; The boundary between head and body is not obvious, with large compound eyes and 8 retractable wrists. Each wrist has two rows of fleshy suckers, which can strongly absorb other things. The base of the wrist is connected with a reticular tissue called the skirt, and there is a mouth in the center. There are a pair of sharp horny palates and file-like toothed tongues in the mouth, which are used to drill through shells and scrape off their meat.

Octopus sucks water into the mantle, breathes it and excretes it through a short funnel-shaped tube. Most octopuses crawl along the bottom with suction cups, but when they are frightened, they spray water from their body tubes, thus moving quickly in the opposite direction. In case of danger, ink-like substances will be sprayed out as a smoke screen. Some substances can paralyze the attacker's sensory organs.

The most widely known octopus is the common octopus (O. vulgaris), which is of medium size and widely distributed in tropical and temperate waters all over the world. It lives in caves or cracks on the rocky seabed, and its joy cannot be concealed. They mainly feed on crabs and other crustaceans. This species is considered as the smartest invertebrate. It has highly developed cells containing pigments, so it can change the color of its body very quickly, which is also surprising.

Octopus is hermaphrodite. The male body has a special wrist, called stem wrist or crossed wrist, which is used to put the sperm bag directly into the coat cavity of the female body. Common octopus mates in winter. Eggs are about 0.3 cm (1/8 inches) long, with a total number of more than 654.38+million, which are produced under rocks or in caves. A 4-year-old larva? Hatching after 8 weeks, during the incubation period, the female stays beside the egg, cleans the egg with a sucker and stirs the egg with water. The young octopus looks like an adult and is very small. After hatching, it needs to drift with plankton for several weeks, and then sink to the bottom of the water for concealment.

Octopus mainly feeds on shrimps and crabs, but some species also feed on plankton. Many marine fish feed on octopus. Octopus has always been regarded as a delicacy in the Mediterranean, eastern countries and other parts of the world.

The deep sea is full of miracles. They are all kinds of strange things, each showing its "magic power". Octopus, like the familiar cuttlefish, is not a fish, but a mollusk. The octopus is unusual in that it is eight feet long as a belt, and it winds and floats in the water. Fishermen also call octopus "octopus".

Speaking of octopus, it is the "one bully" in the ocean. Octopus is extremely powerful, cruel, aggressive and resourceful, and many marine animals are afraid of it. Octopus is a sensitive animal, and its nervous system is the most complicated and advanced among the invertebrate propellers, including central nerve and peripheral nerve. There are auditory nerve, olfactory nerve and visual nerve in the brain ganglion. Its most developed sensory organ is the eye, which is not only big, but also bulging and motionless, like an owl. The structure of the eyes is very complicated. There is a cornea in front, a sclera around it, and a developed lens that can compete with vertebrates. In addition, there is a small pit in the skin behind the eyes. This unusual nest is used for smelling.

The reason why octopus can run amok in the sea is inseparable from its special "magic weapon" of self-defense and attack.

First of all, octopus has eight sensitive touching wrists, each touching wrist has about 300 suckers, and the pulling force of each sucker is100g. Think about it, no matter who is entangled in its wrist, it is difficult to get away. Interestingly, the octopus's wrist, like the human hand, is highly sensitive to external detection. Whenever the octopus is resting, there are always one or two touch wrists on duty, and the touch wrists on duty are constantly moving, and they are highly alert to the "enemy situation"; If something really touches its wrist lightly, it will immediately jump up and spray thick black ink to hide itself, and take this opportunity to observe the surrounding situation and prepare to attack or retreat. Octopus can spray ink six times in a row, and after half an hour, it can accumulate a lot of ink. Octopus ink is harmless to people.