What Are Crabs?

Crab (páng xiè) belongs to the Soft Crustacea, a decapoda, is a crustacean, the body is protected by a hard shell, and relies on the gills to breathe. It is similar to shrimp, lobster, and hermit crab in taxonomy.

Most species of crabs live in the sea or offshore, and some live in freshwater or land. Common crabs include barracuda crabs, barracuda crabs, blue crabs, and Chinese mitten crabs (river crabs, hairy crabs, and freshwater crabs).

Chinese scientific name: crab
Latin scientific name: Brachyura
nickname: crab
boundary: animal world
door: Arthropoda
Asia Gate: Crustacean

Tsuna: Soft Armor
Subclass: True soft subclass
Head: Decapoda
Asia: Gastropoda
distribution area: widely distributed
English name: crab
Next: Short tail

Crab body features

The crab's body is divided into a head, chest and abdomen. The back of the head and chest is covered with a head breastplate, shaped

Chinese crab Variety. The center of the forehead has the first and second pairs of antennae, and the outside is a compound eye with a handle. The mouthpiece includes 1 pair of big jaws, 2 pairs of small jaws, and 3 pairs of jaw feet. There are 5 pairs of pectoral feet on both sides of the head and breastplate. The abdomen is degenerate, flat and zigzag on the ventral surface of the head and chest. The male abdomen is narrow and long, mostly triangular, and only the first two pairs of appendages are deformed into adapters. The female abdomen is broad, and the second to fifth sections each have a pair of double-branched appendages with dense bristles for holding eggs. Most crabs are marine, with the most tropical shallow water species. ^[1]

Crab life habits

A small portion of crabs grow and reproduce entirely in fresh water, and they mostly inhabit rocks under mountain streams. There are also a few crabs such as ground crabs that can adapt to land life, burrowing in wet mud holes, and migrating to the sea during breeding. Most crabs are omnivorous. Some crabs are carnivorous, such as pike crabs which can fish, shrimp and molluscs. A few crabs, such as the window crab, scrape or filter algae and organic debris. ^[1]

Main crab species

There are about 4,700 species worldwide and about 800 species in China. It can be divided into 6 categories: Sponge Crab Dromiacea, Ancient Short-tailed Archaeobrachyura, Point-mouthed Oxystomata, Point-headed Oxyrhyncha, Zodiac Cancridea, Short-ranged Brachyrhyncha. Common genus of male crabs, barracudas, brook crabs, fiddler crabs and mitten crabs. The genus Porcelain crabs, cicada crabs, mimicry crabs, hermit crabs, coconut crabs, etc., are also called crabs, but they are different from the real crabs in the short-tailed order, and are not included here. ^[1]

The main foods are Barracuda tricuspidium, Barracuda crab, blue crab and Chinese mitten crab. ^[1]

Crab

Commonly known as white crabs and barracudas, they are rich in nutrition and delicious in taste. They are important economic crabs for marine fishing and breeding in China. The fishing and breeding output in 2016 reached 542,100 tons and 125,300 tons respectively. Barracuda crabs can easily die and become spoiled. ^[2]

Crab crab

One of the important marine economic crabs on the southeast coast, mainly distributed in Hainan, Guangdong, China

Blue crab In the coastal waters of western, Guangdong, Fujian, Zhejiang and Taiwan, the marine aquaculture production in 2017 was nearly 152,200 tons, and the marine fishing output was nearly 79,500 tons. The crab-like crab has the characteristics of fast growth, big body and delicious meat. ^[3]

Crab mitten

Also known as river crab, hair crab, water crab, hairy crab. It has the distinctive features of "blue back, white belly, golden claws, and yellow hair". It has 4 frontal cusps with deep cuts between the inner frontal teeth, showing a "U" or "V" shape. ^[4]

Crab nutrition facts

Each edible portion of crab contains 17.5 grams of protein, 2.8 grams of fat, 182 milligrams of phosphorus, 126 milligrams of calcium, and 2.8 milligrams of iron, and is rich in vitamin A and vitamin B ₁ . ^[5]

Take Saw margin crab as an example to analyze its nutritional composition:

The components of Serrata serrata are rich in protein, and the content of female gonads is as high as 30.98%.

Blue crab The highest protein content. In addition, the protein and amino acid types of S. serrata are complete, with essential amino acid scores ranging from 84.23 to 93.58. ^[6]

The crab body is rich in fat and unsaturated fatty acids (UFA). Muscle has a UFA of 74.58%, an EPA of 18.04%, and a DHA of 13.52%. The content of unsaturated fat in S. serrata is high, especially the omega-3 fatty acids, EPA, and DHA that cannot be synthesized in the human body. EPA can significantly reduce the triglyceride (TG) and cholesterol (TC) values in the serum and anti-platelet Gathering delays thrombosis, prevents cardiovascular and cerebrovascular diseases, and prostate hyperplasia. DHA can promote brain development, enhance brain learning and memory, and prevent brain aging. ^[6]

Saw margin crab is a high-K low Na food. Saw margin crab is more conducive to hypertension patients. Its liver has a very high Ca content, second only to stone snails, catfish, shrimps, shrimp skins, and cloves, and natural organic calcium is easy for the body to digest and absorb. The contents of other essential elements Mg, Fe, Cu, Zn, Mn, etc. in the blue crab are also high. The selenium content of each component of blue crab is very high, especially the female gonad. ^[6]

Crab main value

Serve.

Crab shells can be used to refine industrial raw materials, chitin, and can also be used to produce glucosamine. Some crabs are used in Chinese medicine. Crab larvae or adults can be used as bait and feed. In addition, some crabs can damage farmland water conservancy or act as intermediate hosts for human parasites. ^[1]

Crab farming technology

Crab Location Selection

Appropriate crab breeding sites should have good water quality, sufficient water sources, and convenient drainage. In order to ensure good air permeability, sandy land or sandy land should be mainly used. The water depth in the pond should be controlled at about 1m, and the shallowest place should not be lower than 10cm. In the built pond, there are several mounds in which the aquatic plants such as reed, iris white, and calamus are planted. On the one hand, these aquatic plants are a good source of nutrients for crabs to eat. On the other hand, it is conducive to consolidating the river embankment and avoiding water leakage caused by burrowing. ^[7]

Crab Crab Selection

Crab seedlings Variety is the key to achieving high yields. At present, the majority are Yangtze River Mitten crab seedlings. At the same time, ensure that: physical fitness, neat specifications and good adaptability. Select a good crab fry, first soak it in the pond for a few minutes, repeat the operation several times, observe the crab's ability to adapt to water quality, and put it in when there are no adverse reactions. At present, the polyculture of crab fry and other fish species is mainly used to provide a source of food for crabs on the one hand and increase economic benefits of breeding on the other. ^[7]

Crab management measures

Crab feeding management , river crabs eat fresh ingredients. For this reason, daily feed management prohibits feeds that have been stored for a long time and have deteriorated. At this stage, it is still necessary to mainly place meat feeds, with appropriate nutritional vegetarian diets, especially more plant-based feeds, so as to ensure good water quality in the pond. The number of times the material is used should be determined according to the change of climatic temperature. In the hot summer, you can feed it once or twice. The specific number depends on the weight of the crab. If there are residues that have not been eaten, they should be salvaged immediately to avoid deterioration and affect water quality. ^[7]

Crab breeding management , strengthen daily feeding management, and implement daily inspections. Inspect at least 1 or 2 times a day, once in the morning and evening, and pay attention to the foraging situation of river crabs. When there is any abnormal situation, you should immediately check whether there is any disease, and you can actively use the medicine to prevent the spread of infectious diseases and affect the breeding efficiency. With the increase of the breeding quantity, the situation of hypoxia in the water body occurs from time to time, and the water exchange and aeration should be done in time to reduce the high mortality caused by hypoxia. In addition, the pond should be checked for leaks, and blocked to prevent invasion of natural enemies, and to avoid running away. ^[7]

The disinfection and management of crabs removes germs and bacteria from ponds, and creates a good breeding environment for healthy breeding of river crabs. Before and after breeding, disinfection management of the pond should be done well. Before the young crabs enter the pond, they should be disinfected in advance, and the sludge in the pond should be cleaned in time in winter. During the breeding management process, the selected disinfectant requires: low toxicity and fast volatility to avoid environmental damage caused by disinfection. ^[7]

Prevention and treatment of common crab diseases

During crab farming, the occurrence of some diseases seriously affects the efficiency of the farm. For example, the local prevalence of crust ulcer disease is extremely high. Typical symptoms: At the beginning of the epidemic, crab shells have multiple brown spots with a reddish middle depression. In the late stage of the epidemic, the color of the spots became black, the symptoms of ulcers worsened, and they began to erode, even the crab's body was clearly visible. The local epidemic rate is extremely high, which is more harmful and affects the ultimate breeding benefits. The best way to treat, on the first day, use 10% povidone iodine, use 250mL / 667m ² , mix with water and spread evenly. The next day, 30% vitamin C was used, and 250g / 667m ^{2 was} mixed with water and spread evenly. The harm of this disease affects water quality. In daily control, disinfection should be done well, and water quality management should be strengthened. ^[7]

Crab buying tips

Various pictures of crabs (4 photos)

Common sea crabs include barracuda crabs, snow crabs, and blue crabs. Among them, snow crabs basically die from the water after being caught, and barracuda can be farmed artificially. The quality of the food ingested by pike crabs and snow crabs is better than the growth environment. They can be eaten after death. Choose fresh when choosing: the back shell is blue-black, shiny, full umbilical, and the belly is white. The blue crab burrows in the shallow sea and estuary muddy bottoms. They are carnivorous and sometimes eat corrupt small animals. Once dead, the crab's gastrointestinal tract may have toxins and spread into the muscles, so dead crabs are not suitable for consumption. Blue crabs are best kept in clean fresh brine for temporary purification, which helps to clean up the crab's digestive organs. ^[8]

Crab notes

1. May cause diarrhea. Chinese medicine believes that crabs are cold and salty, and those with spleen and stomach deficiency can easily cause abdominal pain, diarrhea or indigestion. Modern medicine believes that crabs are high in protein and difficult to digest. Solution: Take one at a time, and eat it with warm old vinegar, ginger, and perilla; people with gastrointestinal diseases are not recommended to eat it, and it may worsen the disease. ^[9]

2. May cause gout. Crabs contain two ingredients, purine and glycine, which produce too much uric acid in the blood. People with high uric acid may induce gout. ^[9]

3. Don't drink tea while eating crabs. Tea will dilute the gastric juice, which has a bactericidal effect and can kill the bacteria carried by crabs. The content of tannic acid in tea is high, and the protein in tannic acid and crab meat will produce tannic acid protein, which is more difficult to digest and may cause vomiting, abdominal pain, diarrhea and other symptoms. ^[9]

4. Crabs and persimmons. Because crabs and persimmons are products of the same season, the probability of eating them at the same time is relatively high. The tannic acid contained in persimmon is the same as the tannic acid in tea water, and the symptoms after eating are the same as tea water. Eating both is only for indigestion and is not poisonous. ^[9]

5. May cause itching throughout the body. Crab meat enters the human circulation through the intestinal wall. Large molecules such as proteins, which are not easily broken down, can induce allergic reactions in the human body, manifested as gastrointestinal smooth muscle spasm, itching and even edema. ^[9]

6. Risk of stroke. Crab is a kind of high cholesterol food. Crab yellow is the highest content. It contains 470mg of cholesterol per 100g. The Dietary Guidelines for Chinese Residents recommends that cholesterol intake be controlled within 300mg / day. It is recommended that patients with cardiovascular and cerebrovascular diseases do not eat or eat crab yellow when eating crabs, and it is advisable to accompany meals with less vegetarian food and light. ^[9]

7. Dead crabs and overnight crabs should be discarded. Crabs have a high content of protein. The proteins in dead crabs and overnight crabs will be broken down into histamines and cause allergic reactions, such as vomiting and diarrhea, itching or even edema. ^[9]

8. Don't eat four "parts." Crabs' body surfaces, gills, and gastrointestinal tract are full of pathogens such as bacteria, viruses, and even parasites. Therefore, when eating crabs, you must remove crab gills, crab intestines, crab hearts (commonly known as hexagonal plates), and crab stomachs (that is, triangle-shaped bone packs with sediment inside). Especially drunk crabs, these pathogens are still alive, let alone eat. ^[9]

9. Crab-eating should be paired with alcohol. ^[9]

White wine and dry white have bactericidal effect, refreshing taste, sour taste of white wine can

Awakens the taste buds, giving people a pleasant and refreshing taste.

Red wine: The chemical reaction between tannin of red wine and crab meat can easily remove the fishy smell of crab meat.

Liquor: People with spleen and stomach deficiency have a stomachache and diarrhea when eating crabs. Liquor combined with blood circulation can relieve these discomfort.

Rice wine: It has the effect of improving the taste, among which alcohol can remove fishy smell and sweetness can be freshened. ^[9]

Crab health rumors

Pregnant women cannot eat crabs, this is not necessarily true!

The "coldness" in everyone's mouth is not the reason why pregnant women cannot eat crabs. If you have eaten crabs before pregnancy and there are no problems (no allergies, no symptoms such as diarrhea), you can eat them. Of course, this is also under the premise of healthy eating. However, if a pregnant woman is allergic to crabs before pregnancy or has an adverse reaction after eating crabs. Then you ca nt eat it! ^[10]

Crab plus vitamin C is equivalent to eating arsenic, but this is not the case!

In fact, this year s CCTV s 3.15 party broke the rumor. Although crabs contain arsenic, 90% to 99% of them are non-toxic organic arsenic, and 100 to 200 mg of vitamin C will not produce a large amount through reduction. Toxic trivalent arsenic. ^[10]

Crab can drink beer, and it is suitable for rice wine or white wine. This is not true!

For gout patients, wine and crabs are among the tightly controlled foods. If you have gout or hyperuricemia, no matter what kind of alcohol you should avoid, plus crab, the effect of inducing gout is really strong. For healthy people, drinking a small amount of crab is fine. ^[10]

Crabs are hair products, tumors will relapse and you ca nt eat them. Wrong!

The so-called "fat" usually refers to foods that can aggravate or induce the onset of diseases, but most of these diseases refer to some allergic diseases, such as asthma, urticaria, etc. In fact, whether the tumor recurs and spreads is related to the internal gene regulation of the tumor cells, not caused by eating the so-called "hair". ^[10]

Crab discoloration mechanism

Why does the blue-gray crab turn orange-red when cooked?

The ancients looked at it with amazement and did not understand the mystery. It turns out that

The lower dermis contains red, yellow, blue, and cyan pigment cells. Usually, these pigments are mixed in the carapace, showing a dark gray. Sometimes the color depth changes with the intensity of the external light. The red pigment in the dermis, also known as shrimp red pigment, is a type of carotenoid. When it was heated to 100 degrees Celsius, the other pigments were decomposed and disappeared, but the carotenoids were not destroyed, so that the cooked crabs showed a bright orange-red color. The feet gather more and the abdomen is less, so the cooked crab belly is also a familiar image. ^[11]

Crab Crab Culture

The ancient crab chanting crabs often used "crab yellow", "fat cream" and "tender jade" to describe the deliciousness of crabs. This refers to different parts of crab. "Crab yellow" refers to the purple-brown leaf-shaped ovary in female crabs (which turns yellow when cooked); "fat cream" refers to the colorless transparent gelatinous seminal vesicles of male crabs, which are orange-red blocks when cooked and have " The term "hiding amber in the chest" means "chewing jade" means cheek meat, that is, white and delicate crab meat in the carapace, such as fat and jade. As for describing the crab's "spit pearl", it is the foam formed by carbon dioxide and water when the crab breathes in the water. It is clear and transparent, which proves that this crab is a living thing. ^[11]

The ancient literati regarded crab eating as a pleasure, especially when enjoying crabs. In the Song Dynasty, Fu Xi's "Crab Spectrum" is as strange as: "Crab, with its cross, it is called crab; with its sound, it is called Guo Suo; with its outer bone, it is called Jishi; with its content, it is called intestine. "It also has many elegant names, such as" General Iron Armor "," Intestinal Boy "," Hanging Man "," Han Huangbo "and so on. The book also makes theoretical explanations on the crab's shape, variety, plucking, processing and eating, etc. It has a certain academic value and is an important reference for studying crab culture. ^[11]

Since ancient times, crabs have been regarded as the "three treasures of aquatic products", which is praised by gourmets of all ages. In the Song dynasty, Su Dongpo, a craving for crabs, was obsessed with this thing when he was disappointed in his career. He sighed, "Let's live up to Lushan's eyes, don't eat crabs." "It is ridiculous that Wu Zhongxu obediently guarded him, and a poem was exchanged for two pointed balls." "Tip" refers to the male crab; "Tuan" refers to the female crab. Su Xueshi exchanged poems for fresh crabs, and his pride was overflowing with words and expressions. As a poem, it proves that the desire to eat crabs is much stronger than others. ^[11]

Lu You, a patriotic poet of the Southern Song Dynasty, had a difficult life in his later years and had poor eyesight, but preferred crab eating. Even if I get it, I am very happy, like a urchin. Poetry proves that: "Crab fat temporarily () was born, and the wine green was beginning to pour out old eyes." You see him salivating, hurriedly pouring wine, using fat crabs as a drink, even the dim old eyes are happy. Suddenly brightened. ^[11]

Shixian Li Bai often visits Chang Ji's Orchid Restaurant, who is tired of Western-style beef and mutton, and wants to eat seafood. You Shiyun: "Shake the fan to the restaurant, hold the crab sticks." He felt that sucking crab meat and drinking fine wine was naturally a pleasure. However, from the seasonal perspective, this is summer crab eating, otherwise it will not "shake the fan", and the crab meat is far less delicious than the autumn crab yellow. ^[11]

Su Dongpo likes to eat autumn crabs, and his poem reads: "Half-shell with yellow should be ordered wine, two chewing snow Xue advised to add meals."

crab Therefore, in the early autumn, the yolk of female crabs had just half-shelled yolks, which was not fat in late autumn, but the crab-yellow exuding aroma was still delicious, although it was not full. Therefore, Jiuxing and appetite increased sharply, and even calling for additional meals really called for cooked crabs. The poem is not very much inked, and the appearance of the poem suddenly appeared on the paper, creating an intoxicating artistic appeal. ^[11]

Ming Dynasty Xu Wei's "Title Crab" poem: "The crabs in the rice-cooked Jiangcun are fat, the double chews are like halberds, and if they turn around on the paper, you should see Dong Zhuoum." Xu is an outstanding painter of the Ming Dynasty. I drew an autumn crab. After the appraisal, I suddenly thought about it. If I look over the crab in the painting, it will be a beautiful yellow cream. He gave "dead" a living life, and the richness of his imagination was beyond anyone's reach. The poem eye of this poem is "Dong Zhuo navel". Shi Zai, the male actor Dong Zhuo, had a fat belly and a deep umbilical cord. Later generations agreed that the custom became an allusion, and it was used as a metaphor for something fat and oily. ^[11]

The author of "A Dream of Red Mansions", Cao Xueqin, is both a writer and a gourmet. He is very particular about crab eating, and his poems have won: "Chering a cheek is more happy with Guiyin, and pouring vinegar and ginger is mad. The king and the sun should have wine, but the innocent son has no bowel The coldness between the umbilical cords and forgetfulness, the paper is dyed and washed with perfume. It was originally a beautiful mouth and mouth, and Poshan had laughed for a lifetime. "It can be said that the singing of crab eating is not only the best way and method of crab eating (pouring vinegar) , Ginger, and wine), also told people that the crab is cold in the navel, and it is easy to accumulate cold in the abdomen, so ginger and garlic are used. ^[11]