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 its body color 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. Larvae hatch after 4 ~ 8 weeks. During the incubation period, the female guards the eggs, cleans them with suction cups and stirs them 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.

[Edit this paragraph] Eating habits

Octopus mainly feeds on shrimps and crabs and some 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. Because stable structural myoglobin is a necessary condition for octopus to survive in the deep sea, it is not a problem that octopus likes to eat crustaceans such as shrimps and crabs. Fighting with lobsters is to compete for astaxanthin (astaxanthin in English) resources. Astaxanthin is the strongest antioxidant and a necessary condition to ensure the structural stability of myoglobin from oxidation. According to the accurate quantum calculation by Professor Francesco Buda, a scientist from Leiden University in the Netherlands, and his experimental team members in 2008, mature shrimp, crab and salmon are attractive bright red because they are all rich in astaxanthin, and the natural red substance of mature shrimp, crab and salmon is astaxanthin.

sepia

Also known as cuttlefish and squid, he is the most outstanding smoke expert among cephalopods. Squid [1] (squid, a kind of squid. Cephalopod mollusk, closely related to octopus and squid. Characterized by a thick calcareous inner shell (cuttlefish bone, cuttlefish bone or cuttlebone). There are about 100 species with body length of 2.5? 90 cm ( 1？ 35 inches), slightly flat, with narrow fleshy fins on both sides. * * * There are 10 wrists, 8 short wrists and 2 long wrists for predation, which can be retracted into two capsules; There is a sucker on the wrist and the top of the wrist. It lives in shallow waters in tropical and temperate coastal areas and often moves to deeper waters in winter. Common cuttlefish breed in spring and summer, and the output is about 100? 300 eggs. Squids mainly eat crustaceans, small fish or eat each other. The main enemy is large aquatic animals. The meat is edible, the ink bag can be used to make ink, and the inner shell can be used to feed caged birds with calcium. The modern squid appeared in the Miocene 2 1 10,000 years ago, and its ancestor was arrow stone. In case the enemy hurts, they will smoke and run away. Commonly known as cuttlefish, it has a large catch, delicious meat and rich nutrition, and is the general name of sepiidae animals. Living in the warm ocean, swimming fast, mainly feeding on crustaceans, but also preying on fish and other mollusks. There are giant squid, squid and cuttlefish (commonly known as squid). Common squid in China are cuttlefish and needleless squid.

[Edit this paragraph] classification status

Animal kingdom, Mollusca, Decapoda, Dipranchia, Cephalopoda.

Edit this paragraph shape

The body can be divided into three parts: head, feet and trunk. Trunk is equivalent to visceral mass, covered by muscle sheath and with calcareous inner shell.

head

The front end of the body is spherical, with a mouth at the top, an oral membrane around it and five pairs of wrists around it. There are a pair of developed eyes on both sides of the head, and the structure is complex. There is an oval pit under the back of the eye, called olfactory trap, which is an olfactory organ, equivalent to osphradium of Gastropoda, and a chemoreceptor. Squid feet in the sea

Has been specialized into wrists and funnels. There are 10 wrists, which are symmetrically arranged left and right, with the first pair in the center of the back and 2-5 pairs facing the ventral side in turn. The fourth pair of wrists is particularly long, and the ends expand into tongues, which are called tentacles. It can prey on and contract the human wrist capsule. There are four rows of suckers with handles inside each wrist, and there are only 10 rows of small suckers inside the tongue at the end of the wrist, which is called a tactile stick. The middle sucker of the fourth wrist on the left side of the male degenerates and is specialized as the reproductive wrist or toe arm. It can transport sperm pods to females and play the role of mating device. According to the stem wrist, male and female can be distinguished. On the ventral side of the head, the base of the funnel is wide and hidden in the lumen of the jacket, and there is an oval cartilage depression on both sides of its ventral surface, which is called the attachment groove. It cooperates with the attachment ridges on the left and right sides of the ventral part of the mantle, such as pressing buttons, and is called an attachment, which can control the opening and closing of the mantle hole. The front end of the funnel is a simple water pipe, which is exposed outside the mantle. There is a tongue in the water pipe to prevent the water from flowing backwards. When the locking device is opened, the muscle cuff expands and seawater flows into the cuff cavity from the cuff hole; Tighten the locking device, close the sleeve hole, the sleeve contracts, and the pressurized water is ejected from the water pipe of the funnel. This is the motive force of squid movement.

tree trunk

Bag-shaped, slightly flat on the back and abdomen, behind the head. The muscular capsule outside is the visceral mass inside. There are fins on both sides of the trunk, which are separated at the end of the trunk and play a balance role in swimming. Because there are pigment cells under the skin on the back of the body, the skin can change the depth of color. The orientation of squid's body is based on its living condition in the water, with the head end in front and the trunk end in the back. The side with funnel is the abdomen and the opposite side is the back. However, according to the comparison between mollusk system and squid morphology, the front end should be the ventral surface, because the foot gives way to the ventral side, the back end is the back, the back side is the front, and the ventral side is the back, which is the morphological position of squid, but the former positioning is often used for observation and narration.

[Edit this paragraph] Structure and function

body wall

Squid consists of upper skin, muscle and so on, and has endoskeleton. Epithelium is a monolayer cell with many flat pigment cells under it. The cell membrane is elastic and surrounded by radial muscle fibers. Due to the contraction of muscle fibers, pigment cells expand into stars, muscle fibers relax and pigment cells return to their original state, which can change the depth of skin color. There is also a layer of iris sac under the epidermis, which makes the body surface shiny.

endoskeleton

It consists of an inner shell and cartilage. The inner shell is located in the shell capsule under the skin on the back of the body, which is very developed, with an oval front end and a sharp end. The shell is calcareous, the back is hard, the ventral side is loose, and there are many gaps. The inner shell can not only increase the firmness of the body, but also reduce the specific gravity of the body, which is beneficial to swimming and keeping balance. Cartilage is developed, and its structure is similar to that of vertebrates, but the cells have long branches. The main cartilage is cephalic cartilage, which surrounds the central nervous system and the balance capsule, and has holes on it, from which nerves can protrude. There are also cervical cartilage, wrist cartilage and so on.

digestive system

The digestive tube of squid is U-shaped. In the front of the mouth, in the center of the oral membrane, there is a muscular mouth called mouth ball. It has a pair of parrot beak-shaped jaws, one on the back and the other on the abdomen, which can chop up food. Mouth ball has a toothed tongue at the bottom to help swallow food. There are anterior salivary glands and posterior salivary glands in the mouth. The front saliva is single, and the saliva tube is open on both sides of the tongue, which can secrete mucus; A pair of posterior salivary glands, located at the front and back of the esophagus, have a catheter leading to the entrance ball, which secretes venom and can kill and paralyze captured animals. Mouth ball is connected with a slender esophagus, which is connected with the gastric hilum. The stomach is located at the top of visceral sac. It is long and saccate with muscular walls. The left side of the stomach is a blind sac with folded inner wall and cilia. The intestine is short and thick, turning forward from the pylorus of the stomach, slightly arched, ending in the rectum, and the anus opens in the sleeve cavity, behind the base of the funnel. There are a pair of anal valves on both sides of the anus, the function of which is unknown. A pair of livers, very large, are yellow glands, occupying the first half of the visceral sac and located on both sides of the esophagus. The front end is round and the back end is pointed. A pair of hepatic ducts run backward along both sides of the intestine, and the last two hepatic ducts meet and pass through the blind sac of human stomach. The gland branching on the hepatic duct is the pancreas. The liver can secrete enzymes and input them into the stomach for digestion. The hepatic duct contracts rhythmically and can absorb nutrients from the blind sac and stomach, so it has the function of storing nutrients. The pancreas secretes amylase and protease into the stomach. The digested food is absorbed by the blind sac and the residue is discharged from the anus. At the end of the rectum near the anus, there is a catheter connected with a pear-shaped sac, the ink sac, which is located at the back end of the visceral mass. It is actually a very developed rectal blind sac. The gland in the capsule can secrete ink, which is discharged from the anus through the catheter, and the surrounding sea water becomes dark, thus avoiding the enemy, hence the name of the squid.