appearance
The body can be divided into three parts: the head, the feet and the trunk. The trunk is equivalent to the visceral mass, which is covered by a muscular 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 the olfactory organ, equivalent to osphradium of Gastropoda, and is a chemoreceptor.
foot
Has been specialized into wrists and funnels. Wrist 10, symmetrically arranged left and right, with the first pair in the center of the back and 215 pairs to the ventral side in turn, in which the fourth pair of wrists is particularly long, and the end is tongue-shaped, which is called tentaculararm, which can prey and contract into the wrist capsule. There are four rows of sucker with handle on the inner side of each wrist, and there are only 10 rows of small sucker on the inner side of the tongue at the end of the wrist, which is called tentacularclub. The middle sucker of the fifth wrist on the left side of the male degenerates, and it is specialized as reproductive wrist or hectocotylizedarms wrists. 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 adheringgroove. It is matched with the adheringridge on the left and right sides of the ventral part of the mantle, such as a snap button, and is called an adheringapparatus, 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.
trunk
Bag-shaped, slightly flat on the back and abdomen, 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.
Structure and function
body wall
It is composed of upper skin, muscle, etc., and has an endoskeleton. The epithelium is a single layer of cells, and there are many flat chromatophore under it. The cell membrane is elastic and there are radial muscle fibers around it. 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
It 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 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, inksac, 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.
respiratory apparatus
A pair of pinnate gills, located on both sides of the front end of the outer lumen. 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 water flows through the gill to complete gas exchange. There are gill glands on the back edge of gill axis, which are rich in blood vessels, which may be related to the nutrition of gill.
circulatory system
The circulation system of squid is basically closed tube, and there are still some blood sinuses. The heart consists of a ventricle and two auricles, which are located in the central pericardial cavity near the rear end of the body. The ventricle is rhombic, asymmetrical, with thick wall, long saccate atrial appendage and thin wall. An anterior aorta extends forward from the ventricle and branches to the head, tunica vaginalis, digestive tract, etc. A posterior aorta extends backward from the ventricle to the tunica vaginalis, rectum, gonad and other organs. Blood flows into the main vein through the microvascular network, and the main vein branches into a renal vein and enters the kidney; The renal vein and the external vein at the back of the body enter the branchiahead at the base of the gill (the wall of the branchiahead 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 blood circulation, metabolites are excreted in the kidney and oxygen-carbon exchange is carried out in the gills. Cephalopods have a very high blood pressure, which can exceed that of vertebrates.
excretory system
A pair of kidneys, a cystic structure, including a dorsal chamber and two abdominal chambers. The ventricles are located on both sides of the back of rectum, and are symmetrical left and right. A pair of renal foramen are opened in the tunica 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 kidney can collect metabolites from the pericardial cavity. There are spongy vein glands around the vein of the kidney, and their branches are hollow and communicate with the vein. These glands have a layer of glandular epithelium with excretory function, which can absorb metabolites from the blood and discharge them into the renal capsule. The dorsal chamber of the kidney is located on the dorsal side of the abdominal chamber, and there is a hole communicating with the abdominal chamber. The excrement of squid does not contain uric acid but guanin.
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 nerve ganglion, visceral ganglion and foot ganglion around esophagus, surrounded by a cartilaginous shell. The dorsal side of esophagus is a pair of cranial nerve ganglia, and the ventral side is a pair of foot ganglia and a pair of visceral ganglia, which are arranged in front of each other. There is also a pair of carpal ganglia, which are located in the anterior part 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, etc. The visceral ganglion extends out of the sheath nerve, and its outer branches form a pair of stellate ganglion on both sides of the funnel base, and its inner branches branch out the cutaneous nerve and fin nerve. It also divides into infundibulum nerve, constrictor nerve, etc.
Two branches of sympathetic nerve branch from the back center of mouth ball's inferior ganglion, and then reach the stomach along both sides of the esophagus, forming an oval gastric ganglion, which is located at the front and ventral surface 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, which is connected to the sclera, and behind the pupil are the lens and the agile muscle; The inner layer is retina, which is mainly composed of rods, and the outer layer is retinal cells. The structure of the eye 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 the visceral ganglion. The capsule is filled with liquid and has an otolith. There is an auditory plaque on the back of the front end of the capsule, and another protuberance called maculastatica is the sensory part. Olfactory depression is located at the back and lower part of the eye, which is epithelial depression with sensory cells, and the nerve ganglion branches off here, which is a chemoreceptor.
genital system
Squid is hermaphroditic, and there is no obvious difference in appearance. Reproduction is in vitro fertilization and direct development.
The female has an ovary, which is formed by the development of body cavity epithelium and located in the reproductive cavity at the back end of visceral mass. When the egg matures, it falls into the cavity, and is exported from the thick fallopian tube with a thin end. The initial opening of female reproduction is in the outer 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 ovipositor glands on the visceral sac walls on both sides of the rectum, which open into the coat cavity, and their secretions also form the shell of eggs and an elastic substance that hardens when it meets water, which can bond eggs into egg groups. There is also a pair of small accessory egg-wrapping glands in front of the egg-wrapping gland, whose function is unknown. During the reproductive 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 end of the body and comes from the epithelium of the body cavity. It is integrated by many tubules, and when the sperm matures, it falls into the reproductive cavity from the tubules. 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 a spermatophoresac, and the end is a penis. The male reproductive orifice is open to the outer jacket cavity. There are many sperm pods in the sperm capsule. Sperm reach the seminal vesicle and are covered with an elastic sheath to form a spermatopod.
Reproduction and individual development
Every spring and summer, cuttlefish 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 is15℃ ~ 20℃, and the salt content is above 30%. Before spawning, male and female mate, 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 females discharged fertilized eggs, which were round, slightly pointed at one end, with a long diameter of 10mm, and gathered together in a string, with a black surface and adhered to foreign objects, commonly known as "sea grapes". Squid eggs contain a lot of yolk, belonging to terminal yellow eggs. After incomplete cleavage (disc cleavage), gastrula is formed by outsourcing and develops directly. The hatched larvae are similar to adults.
There are many kinds of squid in China, and Sepiellamaindroni is the most obvious one, which is abundant in the southern coastal areas of Zhejiang and Fujian. Taiwan Province squid (Loligoformosana) is distributed in the South China Sea area of the Taiwan Province Strait, Shantou offshore and Beibu Gulf as spawning sites.
edibleness
Squid can be said to be a treasure all over the body, delicious to eat and effective in medicine. What is commendable is that it combines the delicious function of food with the medical and health care function. According to the traditional concept of 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, such as cold salad, stir-fried shredded mullet, fried mullet roll, fried mullet soup, sliced mullet, etc., especially braised mullet with fresh garlic moss, which is very delicious. Its eggs are baked into fish glue, and then cooked by the chef, it becomes a famous fine 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 creatures, the squid swims fastest, and its swimming speed is very fast. Unlike ordinary fish swimming by fins, it moves rapidly by the reaction of water spraying from the funnel pipe on its belly, and its spraying ability is like rocket launching. It can make the squid jump from the deep sea and jump out of the water as high as 7 meters to 10 meters. Squid's body is like a cannonball, and it can fly about 50 meters in the air. The speed of squid swimming in seawater can usually reach more than 15 meters per second, and the maximum speed can reach 150 kilometers per hour. Sailfish, 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 admit defeat. Of all the squid in the world, the youngest is the baby squid. Its length is no more than 1.5 cm, which is about the size of a peanut and weighs only 0. 1 g. This subminiature squid lives in the aquatic plants in the shallow sea of Japan, and its appearance is very similar to that of ordinary squid, except that there is a sucker on its back, which can be adsorbed on the aquatic plants and will not be washed away by the sea. Usually, it rests on the aquatic plants. Once it finds its prey, it suddenly attacks. After eating, it returns to the aquatic plants to rest quietly, waiting 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 kingdom of squid, there is also a small firefly squid. It is a luminous creature, with three light-emitting devices on its belly and one around some eyes. The light it emits can illuminate 30 cm away. When it meets a natural enemy, it emits strong light, scaring the natural enemy into running away.
Why can squid ink-jet juice?
The ink in the squid's stomach is a weapon to protect itself. At ordinary times, it roams in the sea and specializes in eat small fish shrimp, but once there is any fierce enemy coming at it, the squid immediately spews an ink from the ink sac, dyeing the surrounding sea water black, so that the enemy can't see it immediately, and under the cover of this black smoke, it runs away. Moreover, the ink it spews also contains toxins, which can be used to paralyze the enemy and make it impossible for the enemy to chase it.
However, it takes a long time to store a bag of ink in the ink sac of squid, so squid will not easily cast ink until it is in a critical situation.
Squids usually like to swim in the open sea, and in late spring, they swim to the offshore in droves to lay eggs. It likes to lay its eggs on seaweed or wood chips and hang them like a bunch of grapes. Therefore, fishermen along the coast often bundle branches and other things into bundles and throw them into the sea to lure squid to lay eggs. When groups of squid swim to lay eggs, they will draw nets and fish again, which will benefit a lot.
The cuttlefish is a delicious seafood with delicious meat, and the ink river in its ink sac is processed for industrial use. Ink sac is also a kind of medicinal material, so the cuttlefish is a treasure all over.
Squid is one of the four major marine 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 the squid body, which contains ink glands that can secrete natural ink. In case of enemy damage or crisis, the ink sac contracts and shoots ink. In an instant, the sea water is "black smoke" and it is dark, so it takes 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 can be called Qiang Bing's expert. Its body is like a rubber bag with its internal organs wrapped in it. 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 long mouth on the top of the head, with horny jaws in the mouth, 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 inner side is densely packed with suction cups, which are called wrists; There are also two long, free-moving feet, which are called wrist-touching, and only the inside of the front end has suction cups. Wrist and wrist-touching are the predation and combat weapons of squid. Not only the weak life will be killed by the squid's wrist, but even the giant whale in the sea is difficult to deal with when it meets a big squid with a length of more than ten meters.
There is also a funnel on the ventral surface of the squid head, which is not only an outlet for reproduction, excretion and ink, but also an important exercise organ of squid. When the squid shrinks, the water in the pocket-shaped body can be rapidly ejected from the funnel mouth, and the squid moves forward rapidly with the help of the reaction force of water, such as a strong crossbow leaving the string. Because the funnel usually points forward, the squid usually moves backwards.
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 squid shells gradually degenerated and were completely buried in the skin, and their functions changed from protection to support. The shell of squid is also called "cuttlebone" and can be used as medicine. Squid lives in the deep ocean, and swims from deep water to shallow coastal areas 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 laying eggs.
Deep-sea squid
1873, the giant squid was first discovered in the "Portuguese" Bay near Newfoundland. At that time, a small 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. 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 died before conducting research. Up to now, there are only over 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 on the reason why it lurked at the bottom of the sea 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 is doomed that it can only 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 guessed 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 the loss of a tentacle will not endanger the life of giant squid.