Why are crab legs blue and purple? And why is the tail of shrimp blue and purple? Is this edible?

That's because the blood of shrimps and crabs is blue, and their blood is rich in astaxanthin, so there is no problem in eating.

Crab (páng xiè): Animal kingdom, Arthropoda, Crustacea, Soft Crustacea, True soft armor Subclass, Decapoda, Gastropoda, Anura. It is a crustacean, its body is protected by a hard shell and it breathes through its gills. Taxonomically, it is the same kind of animal as shrimp, lobster and hermit crab.

Most kinds of crabs live in the ocean or offshore areas, and some live in fresh water or land. They rely on the mother crab to give birth to small crabs, and every time the mother crab will lay a large number of eggs, the number can reach more than one million. Crabs rely on the geomagnetic field to judge their own direction. The amount of genetic material of this kind of organism is complex and varies greatly, often as many as 100 pairs. Common crabs are hairy crabs (river crabs, hairy crabs, clear water crabs) and swimming crabs. China is rich in crab resources, among which the hairy crabs produced in Gucheng Lake, Taihu Lake, gaoyou lake, Yangcheng Lake, Xiefu, Xinghua and Hongze Lake in the lower reaches of the Yangtze River are the top grade.

In order to improve the survival rate of young crabs and increase economic benefits, it is first necessary to breed crabs. In order to make the big-eyed larvae reach the commercial crab, most of them adopt temporary culture technology in plastic greenhouse. Choose one with good water quality and sufficient water resources; Note: The pond with convenient drainage, no water leakage, no water seepage and little silt should not be too large, the water depth should not exceed 1.2m, the east-west direction of the pond is good, and the sunshine is sufficient. Please refer to the construction method of agricultural vegetable greenhouse for the construction of greenhouse.

15 ~ 20 days before the crab seedlings are released, 75 kilograms of quicklime should be sprinkled on each mu for disinfection. After the medicinal properties disappear, it is necessary to feed water with an 80-mesh sieve to cultivate basic bait, transplant aquatic plants (which must be strictly disinfected), and set up necessary escape prevention facilities. Crab seedlings can be shallower when they enter the pool. Conducive to improving the water temperature and the growth of algae and aquatic plants in the water. Feed bait 2 ~ 3 times a day, such as soybean milk, fish, shrimp paste, etc. , and more in the surrounding shallow waters, according to the weight of 4% feeding, and always pay attention to the weather, water sanctions, individual growth, the number of organisms competing for food. With the growth of young crabs, we should also add some plant bait, such as duckweed and other high-quality aquatic plants. In daily management, we should pay attention to water quality regulation, grasp that water quality should be fat and cool, change water frequently, and change water less, so as not to cause drastic changes in water temperature and water level. After about 2 months of cultivation, crabs can be detained.