1, fertilized egg stage
The spawning time of hairy crabs is generally from 65438+February to March of the following year. Due to the low temperature in winter, fertilized eggs develop slowly, and flea larvae usually break out of their shells when the temperature warms up in spring. Modern hairy crabs are mainly cultured artificially, which can shorten the process in an artificial environment. The larvae of fleas that break their shells in the mother will leave the abdomen of the mother crab and begin to live independently.
2. Flea larval stage
The newly hatched flea larvae are very similar to Daphnia in appearance. It takes five molts at this stage, and it usually takes about a month to develop into crab seedlings. Flea larvae are particularly sensitive to light, so they like to come out for food in the morning and evening. Usually it feeds on unicellular algae in the early stage and becomes omnivorous in the later stage, feeding on rotifers and arthropods.
3. Crab seedling stage
In the crab seedling stage, the compound eyes of hairy crabs began to appear, and the spines and tail forks of the body disappeared, replaced by five pairs of chest, feet and abdominal limbs. Because the body surface of crab seedlings began to develop like hairy crabs and their cheeks were fully developed, crab seedlings began to migrate like fresh water areas. With pliers, crab seedlings began to catch aquatic animals, and their body growth also entered a rapid period.
4, bean crab period
After the crab seedlings shed their shells once, they enter the stage of bean and crab. At this stage, the shell is molted every 5-7 days, and the body shape is more and more like an adult crab. Because it is small, like a soybean, it is commonly known as "bean crab". Bean crabs are very sensitive to water quality. Once the water quality is bad, they will run away. It likes to eat aquatic tubular plants and fresh fish and shrimp.
5. crab deduction period
At this stage, the weight of hairy crabs has reached about 25 grams, and the appearance is no different from that of adult crabs. Crabs will migrate to lakes and rivers rich in food and settle down. Crab farmers also like to buy this kind of buckle crab and put it in, which can save a lot of time.
6. Yellow crab stage
When the young crab grows to more than 50 grams, it is commonly called "yellow crab" because its back is yellow. At this stage, hairy crabs are physically aggressive, grow rapidly, need a lot of food, and feed on the same kind during molting. Crab farmers should pay attention to putting more screws, small fish and other foods, and the breeding density should also be controlled.
7. Crab-forming period
Usually after August of the lunar calendar, hairy crabs at this stage have finished their last molting. The body weight also reached more than 150g, and the gonads began to mature. The size will not increase again, but will only increase muscles and internal organs. Reproductive migration also occurs at this stage. In order to maintain normal growth and development, people begin to eat a lot. Its nutrients began to be stored in the liver in large quantities, making hairy crabs fat, so the best season to eat crabs is in autumn.
8. Love crab period
That is, adult crabs migrate into the sea, and after being stimulated by seawater, their gonads develop rapidly and they begin to have reproductive desires. Hairy crabs will age rapidly until they die after completing their reproductive tasks. Male crabs in the Yangtze River estuary generally enter the death period from April to May, while female crabs will not die until June to July if they want to hold eggs.
Extended data:
Nutritional value of hairy crabs;
Crab is rich in nutrition and contains many vitamins, among which vitamin A is higher than other terrestrial and aquatic animals, vitamin B2 is 5-6 times higher than meat, 6- 10 times higher than fish and 2-3 times higher than eggs.
The content of vitamin B 1 and phosphorus is 6- 10 times higher than that of common fish. Every 65438 000g of crab edible part contains 65438 07.5g of protein, 2.8g of fat, 65438 082mg of phosphorus, 65438 026mg of calcium and 2.8mg of iron. Crab shell is not only rich in calcium, but also contains crab red and crab yellow Modern research has found that crab shell contains a substance ACOS-6, which has low toxicity and immune activation characteristics.
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