What is the picture of three swimming crabs? Why does yellow bottom plate and yellow gills appear when breeding

Portunus trituberculatus has become one of the most important economic species in pond culture in China because of its fast growth, large size and delicious meat. Now artificial culture is more common, so what is the picture of Portunus trituberculatus? Why does the phenomenon of yellow floor and yellow Gill appear when raising Portunus trituberculosis?

What is the picture of Portunus trituberculatus?

The main results are as follows: 1. The head and chest nail is fusiform and slightly raised. There are 3 prominent verrucous eminence on the surface, 1 in the gastric area and 2 in the central area. Its shape is like an oval and its ends are pointed like a weaving shuttle, so it has the name of Portunus trituberculatus. There are 9 serrations on each of the two anterior lateral edges, and the 9th serrations are especially large and extend to the left and right. The frontal margin has 4 small teeth. There is a pair of compound eyes with handle that can rotate on both sides of the forehead. Five pairs of chest feet. The stinging foot is well developed, the long node is prismatic, and the inner edge has obtuse teeth. The fourth pair of foot knuckles are as flat and thin as oars, suitable for swimming. The abdomen is flat (commonly known as the crab navel), the belly of the male crab is triangular and the female crab is round. The back of the male crab is green, the female crab is purple, and the ventral side is grayish white.

2. The body color of Portunus trituberculatus varies with the surrounding environment. Individuals living in the sand bottom, the head and chest nail is light grayish green, the anterior Gill area has a round white spot, most of the chelate feet are purplish red with white spots, some or the whole ventral surface is white, the first 3 pairs of long foot nodes and wrist nodes are also white, the palms are blue-white, soft hair brown, knuckles purplish blue or purplish red, the fourth pair of steps are green with white spots, fingertips purplish blue. Individuals who live among seaweeds are darker. For omnivorous, fish, shrimp, shellfish, algae all eat, and even eat the same kind, like to eat animal carcasses.

Second, why does the phenomenon of yellow floor and yellow Gill appear when raising Portunus trituberculatus?

The main results are as follows: 1. The upper part of Portunus trituberculatus may be due to the decline of its oxygen-carrying capacity due to the edema of the crab's yellow gills, which is similar to that of hypoxia, leaning against the edge of the pond.

2. The yellow floor of Portunus trituberculatus is mostly caused by poor bottom quality and no molting for a long time.

(1) the cause of poor bottom quality.

① aquaculture pond is an old pond for many years, which is not completely desilted at the beginning of the year, but simply repair the ring ditch, which has a lot of silt and poor sediment.

In the middle and later stage of ②, the feeding of pellet and bait fish increased, the residual bait and shrimp and crab feces also increased, and the bottom changing frequency was low, which led to the deterioration of pond bottom.

③ uses inferior fertilizer paste and chemical fertilizer, does not pay attention to replenishing bacteria and transferring water, and many fertilizers are not fully absorbed by algae in the fertilizer deposition ponds. At the same time, the culture process does not pay attention to improving the bottom quality, resulting in the increase of harmful substances and deterioration of the pond bottom.

(2) the reason for not molting

Due to the continuous high temperature and low dissolved oxygen in ① in mid-late July and early August, some Portunus trituberculatus may shed their primary or even secondary shell less, and the yellow floor is easy to appear in the crabs without molting for a long time.

② animal feed (bait fish) is insufficient, and some pond mouths are mainly fed with sesame shrimp. Insufficient feeding of bait fish can easily lead to the decline of swimming crab's physical fitness and affect its molting.

③ usually does not pay attention to calcium and mineral supplement, with the growth of shrimp and crab, calcium, magnesium and some trace elements in pond water are gradually used, not replenished in time, the shrimp and crab are easy to molt, difficult or even not molting.

Suggestions for handling:

1. Pay attention to strengthening the improvement of pond bottom quality, and regularly use chemical bottom change "bottom black an" or "ozone water safety" with biological bottom change to improve pond bottom.

2. Pay attention to replenishing bacteria and less fertilizer in the middle and later period of culture. in fact, there is plenty of fertilizer in the pond in the middle and later period, so we can use beneficial bacteria such as "probiotics" or "milk enzyme" to regulate algae.

3. In the ponds with a large number of swimming crabs, strengthen the feeding of animal bait, enhance nutrition, and promote the fattening of swimming crabs. The price will be better when the crabs are fattened.

4. Supplement calcium regularly to keep shrimp and crab absorb enough calcium, promote molting and reduce the probability of unsuccessful molting and non-hard shell.