Octopus sucks water into the mantle and excretes it through a short funnel-shaped body tube after breathing. Most octopuses crawl along the bottom with suction cups, but when they are frightened, they will spray water from the body tube, thus moving quickly in the opposite direction. When in danger, ink-like substances will be ejected as a smoke screen. Some kinds of substances can paralyze the attacker's sensory organs. The most well-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 crevices on the rocky seabed and can't hide its joy. They mainly feed on crabs and other crustaceans. This species is considered to be the most intelligent invertebrate, and it has highly developed cells containing pigments, so it can change its body color very quickly, which is also surprising. Octopus is dioecious. The male body has a specialized wrist, called the stem wrist or the cross wrist, which is used to put the sperm bag directly into the female body's coat cavity. Common octopus mates in winter. Eggs are about .3 cm (1/8 inch) long, with a total number of more than 1,, which are produced under rocks or in caves. The larvae hatch after 4 ~ 8 weeks. During the incubation period, the females guard the eggs, clean them with suction cups and stir them with water. Young octopus looks like an adult and is 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] Feeding habits

Octopus mainly feeds on shrimp and crabs, and some plankton. Many marine fish feed on octopus. In the Mediterranean region, eastern countries and some other parts of the world, octopus has long been regarded as a delicacy. 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 shrimp 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 without oxidation. According to Professor Francesco Buda, a scientist from Leiden University in the Netherlands, and members of his experimental team in 28, it was found through accurate quantum calculation that the ripe shrimp, crab and salmon are attractive bright red because they are all rich in astaxanthin, and the natural red substance of ripe shrimp, crab and salmon is astaxanthin.

Sepia

, also known as cuttlefish and cuttlefish, is the most outstanding smoke expert among cephalopods. Squid [1] (Sepia officinalis, a kind of squid. Sepioidea) marine cephalopod mollusk, closely related to octopus and squid. Characterized by a thick calcareous inner shell (cuttlefish bone, cuttlefish bone or cuttlebone). There are about 1 species with a body length of 2.5? 9 cm (1? 35 inches), slightly flat, with narrow fleshy fins on both sides. * * * has 1 wrists, 8 short wrists, and two long wrists for predation, and can be retracted into two capsules; There is a sucker at the top of the wrist and the wrist. Living in shallow waters along tropical and temperate coasts, it often moves to deeper waters in winter. Common squid breeds in spring and summer, producing about 1? 3 eggs. Sepia species 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 fed to caged birds to supplement calcium. The modern squid appeared in the Miocene 21 million years ago, and its ancestors were arrow stones. In case of enemy's harm, they will spray smoke and then escape. Commonly known as cuttlefish, the fishing catch is large, the meat is delicious and nutritious, which 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, cuttlefish, cuttlefish (commonly known as squid), etc.) Common cuttlefish in China are cuttlefish and needleless squid.

[ Edit this paragraph] Taxonomic status

Cephalopoda, Dibranchia, Decapoda, mollusk kingdom

[Edit this paragraph] Appearance <

The head

is spherical at the front end, 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 the olfactory organ, equivalent to osphradium of Gastropoda, and is a chemoreceptor. The squid feet in the sea

have been specialized into wrists and funnels. There are 1 wrists, which are symmetrically arranged left and right, with the first pair in the center of the back and 2-5 pairs to the ventral side in turn. The fourth pair of wrists is particularly long, and its end is tongue-shaped, which is called a tentacular arm. It can prey and contract into the wrist capsule. There are 4 rows of sucker with handle on the inner side of each wrist, and only 1 rows of small sucker on the inner side of the tongue-shaped part at the end of the wrist, which is called the tactile club. The middle sucker of the fourth wrist on the left side of the male degenerates, and it is specialized as the reproductive wrist or hectocotylized arms. It can transport sperm pods into the female body 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 adhering groove. It is matched with the adhering ridge on the left and right sides of the ventral part of the mantle, such as a snap button, and is called an adhering apparatus, 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 water from flowing backwards. When the locking device is opened, the muscular cuff expands, and seawater flows into the cuff cavity from the cuff hole; Fasten the locking device, close the sleeve hole, the sleeve shrinks, and the pressurized water is sprayed from the water pipe of the funnel. This is the motive force of squid movement.

The trunk

is bag-shaped, with a slightly flat back and abdomen, and is located behind the head. The tunica with well-developed muscles 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 according to its living condition in water, the head end is front, the trunk end is back, the side with funnel is abdomen, and the opposite side is back. However, according to the comparison between the mollusk system and the morphology of the squid, the front end should be ventral, 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 the squid, but the former positioning is often used for observation and narration.

[ Edit this paragraph] Structure and function

Body wall

Sepiella is composed of upper skin, muscle, etc., and has an endoskeleton. The epithelium is a single layer of cells, under which many chromatophore are flat, and the cell membrane is elastic, surrounded by radial muscle fibers. Due to the contraction of muscle fibers, the pigment cells expand into a star shape, the muscle fibers relax, and the pigment cells return to their original state, which can change the depth of skin color. There is also an iridocyste under the epidermis, which makes the body surface shiny.

endoskeleton

consists of an inner shell and cartilage. The inner shell is located in the shell capsule under the skin on the dorsal side of the body, which is very developed, with a long oval front end and a pointed protrusion at the end. The shell is calcareous, hard on the back, loose on the ventral side, with 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 helps to maintain 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 the nerves can extend. There are also cervical cartilage, wrist cartilage and so on.

digestive system

the digestive tube of the squid is u-shaped. At the front of the mouth, in the center of the oral membrane, there is a muscular oral cavity, called mouth ball, which has a pair of parrot-beak-like 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 and posterior salivary glands in the mouth. The pre-saliva is single, and the saliva tube opens on both sides of the tooth tongue, which can secrete mucus; A pair of posterior salivary glands, located at the back of the front end of 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 hilum of the stomach. The stomach is located at the top of visceral sac, with a long saccular shape and a muscular wall. On the left side of the stomach is a blind sac with folded inner wall and cilia. The intestine is short and thick, turning from the pylorus of the stomach to the front, slightly arching, ending in the rectum, with the anus opening in the jacket cavity and 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 liver, very large, are yellow glands, occupying the first half of visceral sac, located on both sides of 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 latter two ducts meet and pass through the blind sac of human stomach. The gland branched 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. Pancreas secretes amylase and protease into the stomach. The digested food is absorbed in the blind sac, and the residue is excreted from the anus. At the end of the rectum near the anus, there is a catheter connected with a pear-shaped capsule, 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, so as to hide from the enemy, from which the name of squid comes.