Excuse me, is squid squid? .

Squid, although it is customary to call them fish, is actually not a fish, but a mollusk living in the ocean. Taxonomically, squid belongs to mollusca-Cephalopoda-Diptera-Decapoda. Squid has two gills as respiratory organs; The body is divided into head, short neck and trunk. There are a pair of developed eyes and wrist feet around the mouth on both sides of the head.

At present, there are two kinds of squid on the market: one is a squid with a large trunk and its name is "squid"; One is squid with a slender trunk. Its name is "soft fish", and the small soft fish is commonly known as "small tube".

Sepiidae (Sepiidae; Squid): 1 Cephalopoda family, commonly known as squid. Mainly distributed in tropical and temperate shallow seas, with about 50 species.

It often moves in the middle and upper layers of shallow water, and its vertical movement range can reach more than 100 meters. It feeds on krill, sardines, whitebait and Xiao Xiong fish, and is also the prey of fierce fish. Eggs are matured in batches and produced in batches. Eggs are wrapped in gelatinous egg sheaths, and each egg sheath contains several to hundreds of eggs according to different species. The amount of eggs laid by different species also varies greatly, ranging from several hundred to tens of thousands.

China squid (commonly known as "squid") is tender in meat, and its dried product is called "dried squid" with excellent meat quality. It enjoys a high reputation in the seafood market at home and abroad, with an annual output of 40,000-50,000 tons. Its main fishing grounds are in China, southern Fujian, Taiwan Province Province, Guangdong and Guangxi, as well as the offshore areas of the Philippines, Viet Nam and Thailand.

cuttlefish

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.

Classification status

Molluscs

Cephalopods; Cephalopoda

Double branchial subclass (double branchial subclass)

Decapoda (Decapoda)

appear

The body can be divided into three parts: head, feet and trunk. The trunk is equivalent to a visceral mass, covered by a muscle sheath and has a 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.

◆ feet

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 human contact with the 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 fifth 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.

◆ suitcase

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.

Structure and function

◆ Body wall

It consists of upper skin, muscles and so on. There is an 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.

◆ Respiratory organs

A pair of pinnate gills, located on both sides of the front end of the external cavity. Each gill has a gill axis with gill leaves on both sides, and the gill leaves are composed of many gill filaments. The gill is densely covered with microvessels, and the water flows through the gill to complete gas exchange. There are gill glands at the posterior edge of gill axis, which are rich in blood vessels, which may be related to the nutrition of gill.

◆ Circulating system

The circulation system of squid is basically closed tube, and there are some blood sinuses. The heart consists of a ventricle and two auricles, located in the central pericardial cavity near the back end of the body. The ventricle is rhombic, asymmetrical and thick-walled, and the atrial appendage is long and cystic with thin wall. The anterior aorta extends forward from the ventricle and branches to the head, sheath and digestive tract. The posterior aorta extends backward from the ventricle to the tunica vaginalis, rectum, gonads and other organs. Blood flows into the main vein through the microvascular network, and the main vein branches into the renal vein and enters the kidney; The renal vein and the external vein after the body enter the gill heart at the base of the gill (the wall of the gill heart is spongy and contractile), enter the gill from the branchial vein, then enter the left and right auricles from the outlet branchial vein and return to the ventricle. In the blood circulation, metabolites are excreted in the kidney, and oxygen-carbon exchange is carried out in the gills. Cephalopods have very high blood pressure, which may exceed that of vertebrates.

◆ Excretion system

A pair of kidneys, a cystic structure, including a dorsal cavity and two abdominal cavities. The ventricles are located on both sides of the back of the rectum, which are symmetrical. There are a pair of renal holes in the capsule cavity on both sides of the rectal end. The pericardial cavity extends into the abdominal cavity with a pair of catheters, and its opening is the renal orifice. The kidneys can collect metabolites from the pericardial cavity. There are spongy vein glands around the veins of the kidney, and their branches are hollow and communicate with the veins. These glands have a layer of glandular epithelium with excretory function, which can absorb the metabolites in the blood and discharge them into the renal capsule. The renal dorsal cavity is located at the back of abdominal cavity, and there is a hole communicating with abdominal cavity. The excrement of squid does not contain uric acid, but guanine.

◆ Nervous system

The nervous system of squid is developed, which consists of central nervous system, peripheral nervous system and sympathetic nervous system. The structure is complicated.

The central nervous system is composed of three pairs of ganglia, such as cranial ganglion, visceral ganglion's ganglion and foot ganglion around esophagus, surrounded by a cartilage shell. On the dorsal side of esophagus are a pair of cranial nerve ganglia, and on the ventral side are a pair of foot ganglia and a pair of visceral ganglion, which are arranged one after the other. There are also a pair of wrist ganglia, which are located in the front of the foot nerve and connected with it. A pair of mouth ball's ganglia are located in front of the brain. The peripheral nervous system consists of nerves extending from the central nervous system. The cranial nerve ganglion sends out the optic nerve and divides the olfactory nerve. Visceral ganglion extends out of the sheath nerve, and its outer branches form a pair of stellate ganglia on both sides of the funnel base, and its inner branches branch off the cutaneous nerve and fin nerve. It is also divided into funnel nerve, contraction nerve and so on.

The two branches of sympathetic nerve branch from the posterior center of mouth ball's inferior ganglion, and then reach the stomach along both sides of esophagus, forming an oval gastric ganglion, which is located on the anterior and ventral sides of the stomach. From this, blind bursa nerve, gastric nerve, intestinal nerve and so on are issued.

Sensory development, eyes, balance sac, olfactory trap, etc. The structure of the eye is complex, and the outermost part is transparent cornea without holes; The middle layer is the sclera, the iris is around the pupil and connected with the sclera, and behind the pupil is the lens and agile muscle; The inner layer is retina, which is mainly composed of rod cells, and the outer layer is retinal cells. The structure of eyes is similar to that of vertebrates, but it is formed by ectoderm invagination. A pair of balance capsules are located in the cartilage of the head, between the foot ganglion and visceral ganglion. The capsule is filled with liquid and has otoliths. There is a static macula on the back of the anterior end of the capsule, and another protrusion called static ridge is the sensory part. Olfactory depression is located in the back and lower part of the eye, which is an epithelial depression with sensory cells. Ganglion branches here and is a chemoreceptor.

(8) Reproductive system

Squid is hermaphrodite and there is no obvious difference in appearance. Reproduction is in vitro fertilization and direct development.

The female has an ovary, which is developed from the epithelium of the body cavity and located in the reproductive cavity at the back end of the visceral mass. When the egg matures, it falls into the cavity and exits from the thick and thin fallopian tube. The initial opening of female reproduction is in the external cavity in front of the gill base. There is a fallopian tube gland near the end of the fallopian tube, and its secretion forms the shell of the egg. There are a pair of large oviposition glands on the visceral sac walls on both sides of the rectum, which open in the capsule cavity. Their secretions also form the shell of eggs and an elastic substance that hardens when it meets water, which can bond eggs into egg balls. There is also a pair of small accessory oocyte glands in front of the oocyte gland, whose function is unknown. During the breeding season, eggs mature in batches and are produced in batches.

The male has a testis, which is located in the reproductive cavity at the back of the body and comes from the epithelium of the body cavity. It is made up of many tubules, and the sperm falls into the reproductive cavity after maturity. The vas deferens is long and tortuous. There are seminal vesicles and prostate on the vas deferens. The end of the vas deferens expands into the seminal vesicle, and the end of the vas deferens is the penis. The male reproductive foramen is open to the mantle cavity. There are many sperm pods in the seminal vesicle. Sperm reaches the seminal vesicle and is covered by elastic sheath to form sperm pod.

Reproduction and individual development

Every spring and summer, squid swim from deep water to shallow water to lay eggs, which is called reproductive wandering. According to the situation near Qingdao, the suitable temperature for spawning is 15℃ ~ 20℃, and the salt content is above 30%. Male and female mate before spawning, that is, the male sends the sperm pod into the female coat cavity with the stem wrist, and the sperm pod ruptures, releasing the sperm inside, and the sperm egg is fertilized in the coat cavity. Shortly after mating, the female worm excretes fertilized eggs, which are oval, slightly pointed at one end, with a long diameter of 10mm, clustered together in a string, with a black surface and foreign bodies attached, commonly known as "sea grapes". Squid eggs contain a lot of yolk, which belongs to terminal yellow eggs. After incomplete cleavage (discolysis), the gastrula is formed and develops directly. The hatched larvae are similar to adults.

There are many kinds of squid in China, among which Sepiella maindroni is the most obvious one, which is abundant in the coastal areas of southern Zhejiang and Fujian. Taiwan Province squid (Loligo formosana) is a kind of squid in Taiwan Province Province, which is distributed in the South China Sea of Taiwan Province Strait, Shantou offshore and Beibu Gulf as spawning grounds.

Edible

Squid can be said to be the treasure of the whole body. It tastes delicious and is effective as medicine. What is commendable is that it combines the delicious function of food with the health care function. According to the traditional concept of traditional Chinese medicine, there are two kinds of treatment: drug therapy and dietotherapy, and dietotherapy is to combine the delicious function and medicinal value of food, which is in line with the traditional medical concept and close to the concept of modern health food.

There are many ways to eat squid, including cold salad, fried shredded mullet, fried mullet roll, fried mullet soup, sliced mullet and so on. Especially the mullet braised with fresh garlic moss is very delicious. Its eggs are baked into fish glue, and then cooked by chefs, becoming a famous food at home and abroad. In addition, the viscera of cuttlefish can be squeezed into viscera oil, which is a good raw material for tanning. Its eyes can be made into eyeball glue, which is the first-class glue and agent.

Interesting squid

Among marine life, squid swims fastest, and its swimming speed is very fast. Unlike ordinary fish swimming by fins, it moves quickly by the reaction force of water sprayed from the funnel tube on its stomach, and its spraying ability is like rocket launching. Can make squid jump from the deep sea and jump out of the water as high as 7 meters to 10 meters. Squid's body, like a cannonball, can fly about 50 meters in the air. Squid's swimming speed in seawater can usually reach more than15m per second, and the highest speed can reach150km per hour. The swordfish, which is known as the champion of swimming speed among fish, has a speed of only 1 10 km per hour, so it has to give up. Of all the squid in the world, the youngest is the little squid. Its length is no more than 1.5 cm, which is about the size of a peanut, and its weight is only 0. 1 g. This subminiature squid lives in aquatic plants in the shallow sea of Japan, and its appearance is very similar to that of ordinary squid, except that it has a sucker on its back, which can be adsorbed on aquatic plants and will not be washed away by seawater. Usually, it lives on aquatic plants. Once it finds its prey, it will suddenly attack. After eating, it will return to the aquatic plants to rest quietly and wait for the next prey. The biggest squid in the world is the king squid. They generally live in the depths of the ocean, rest in the deep sea during the day and swim to the shallow sea for food at night. In the squid kingdom, there is also a small firefly squid. It is a luminous creature with three luminous devices in its abdomen and one around some eyes. The light it emits can illuminate 30 cm away. When it meets a natural enemy, it will emit strong light, scaring the natural enemy to escape.

Why can squid be juiced by inkjet?

The ink in the squid's stomach is a weapon to protect itself. At ordinary times, it roams in the sea, specializing in eat small fish shrimp, but once any fierce enemy comes at it, the squid immediately sprays an ink from the ink sac, dyeing the surrounding sea water black, so that the enemy can't see it immediately. Under the cover of this black smoke, it runs away. Moreover, the ink it emits also contains toxins, which can be used to paralyze the enemy and make it impossible for him to pursue.

But it takes a long time to store a bag of ink in the ink sac of the squid, so the squid will not easily throw ink until it is in a crisis.

Squids usually like to swim in the open sea. In late spring, they swim to the offshore in groups to lay eggs. It likes to lay eggs on seaweed or sawdust and hang them like a bunch of grapes. Therefore, fishermen along the coast often bundle branches and other things into a bundle and throw them into the sea to lure squid to lay eggs. When groups of squid swim to lay eggs, they will pull the net again and benefit a lot.

Cuttlefish is a delicious seafood with delicious meat, and the Mohe River in its ink sac is processed for industrial use. Ink sac is also a kind of medicinal material, so cuttlefish is a treasure all over.

Squid is one of the four major seafood products in China (large yellow croaker, small yellow croaker, hairtail and squid). It can not only swim fast in the sea like a fish, but also has a set of stunts to cast a "smoke screen". There is an ink sac in squid body, which contains ink glands that can secrete natural ink. In case of enemy injury or crisis, the ink sac shrinks and shoots ink. In an instant, the sea was black and dark, and it took the opportunity to escape. It can also use the toxins in ink to anesthetize small animals, so it is also called cuttlefish. In fact, squid is not a fish, but a descendant of mollusks.

Among mollusks, squid is an expert in Qiang Bing. Its body is like a rubber bag with internal organs inside. There are fleshy fins on both sides of the body, which are used for swimming and keeping balance. The head is short and there are developed eyes on both sides. A mouth that grows on the top of the head has a horny jaw and can bite food. Squid's feet are born on the top of the head, so they are also called cephalopods. Eight of the 10 feet on the top of the head are short, and the inside is densely covered with suckers, which is called the wrist; There are also two long feet that can move freely, called touching wrists, and only the inside of the front end has suction cups. Wrist and wrist touching are the hunting and fighting weapons of squid. Not only the weak life will be killed by the squid's wrist, but even the giant whale in the sea will be difficult to deal with when it meets a squid more than ten meters long.

There is also a funnel on the ventral surface of squid head, which is not only an outlet for reproduction, excretion and ink discharge, but also an important exercise organ of squid. When the squid shrinks, the water in the bag-shaped body can be quickly ejected from the funnel mouth, and the squid moves forward quickly with the help of the reaction force of water, such as a strong crossbow leaving the string. Squid usually moves backwards because the funnel usually points forward.

The special structure of squid body enables it to swim quickly. In order to adapt to this swimming style, in the long-term evolution process, the shell of squid gradually degenerated and was completely buried in the skin, and its function changed from protection to support. The shell of squid is also called "cuttlebone" and can be used as medicine. Squid lives in the deep sea and swims from deep water to shallow sea to lay eggs in the warm spring breeding season every year. This phenomenon is called reproductive migration, and a large number of squid die offshore after spawning.

Deep sea squid

1873, giant squid was first discovered in "Portugal" Bay near Newfoundland. At that time, a boat was suddenly attacked by this big guy. Fortunately, the owner cut off one of its tentacles with an axe, which was 5 meters long and about 0.3 meters in diameter, and escaped by luck. Since then, people have been tracking the "squid king", but it is annoying that it rarely appears in shallow water. When it surfaced, it was either dead or dying, and it died before it was studied. So far, there are only more than 250 samples available for study in the world, which are either incomplete or seriously damaged. Exactly where it lives, how to live, how to feed and reproduce, is still blank in scientific literature.

By dissecting the body of the giant squid, scientists also speculated why it had been lurking on the seabed for many years. The giant squid's big eyes with a diameter of 25 cm have adapted to the dark environment in the deep sea, so when it comes out of the sea, it will be blinded by strong light and become fragile. This doomed it to live a "shady" life.

Scientists said: "The biggest feature of giant squid is that it has a pair of extremely long tentacles. The length of this pair of tentacles can reach two-thirds of the total length of its body. " Scientists say that they had previously suspected that giant squid was a slow-moving animal. But after witnessing it with my own eyes, I found that it is far more active than originally thought, and it is an active and fierce predator. Scientists say that losing a tentacle will not endanger the life of giant squid.