What is the significance of molting in the life of Macrobrachium rosenbergii?

Molting is a key problem for the growth and health of shrimp, which is directly related to the development of larvae, the growth of larvae and adults, and the spawning and reproduction of parent shrimp. Shrimp molting generally occurs in the following situations: ① growth molting; ② reproductive molting; ③ Regeneration and molting. Before molting, the epithelial layer secretes an enzyme to dissolve the inner epidermis of the old skin. In this way, the outer epidermis is separated from the upper epidermis, and under the front epidermis, the upper epidermis secretes a new epidermis. At the same time, the new epidermis absorbs a lot of old epidermis decomposed by enzymes and a lot of water, which makes the old epidermis crack and shrimp can't get out of it. According to the physiological changes of molting process, it can be divided into the following five stages:

Stage a

Shrimp falls off from its old shell and does not eat or move.

B-order

The body wall is gradually calcified, and you can not eat for 1 ~ 2 days.

C stage

Continue to calcify, start eating, and the epidermis becomes hard.

D stage

The new outer skin began to secrete, gradually fasted and used the metabolites in the body to live.

E stage

Separated from the old shell, it absorbs a lot of water (called hydration) and gains 50% weight.

Hydration can quickly strengthen the new shell, and the most obvious change is that the calcium core of the pigment layer quickly forms hexagonal crystals from irregular shapes. Hydration is the key to the physiological changes of shrimp.

The above is the growth and molting under normal living conditions, and reproductive molting involves the secretion of molting hormone by Y organ and endocrine by X organ. According to the shrimp without eyestalk, in D stage, the secretion of sinus gland (X organ) will increase twice as much as that of shrimp without eyestalk, and there is a lot of "acid phosphorus" secretion in sinus gland. After molting, the acid phosphorus decreased obviously. It is speculated that calcium and phosphorus are the limiting factors for the growth of shrimp molting, and once they are lacking, they cannot grow smoothly.

Macrobrachium rosenbergii generally does not eat or move before molting, and its eyes are not sensitive to light. When the light shines from the side, the newly formed shell shape can be seen at the corner of the lower jaw. When these signs appear, it is a sign that the shrimp will shed its skin. Molting usually takes less than 5 minutes. First of all, the uncalcified membranous part between the breastplate of the head and the back of the abdomen cracked laterally with strong internal force, and then the shrimp almost bent into an inverted U-shape. Furthermore, under the internal force and repeated contraction, the shrimp body is gradually pushed through the cracks in the back.

Shrimp molting is the weakest period of life activity, because it is inactive during A and B and is eaten by other creatures and the same kind. Due to lack of nutrition (mainly calcium and phosphorus) and water pollution, molting fails, or half of molting dies in shrimp shells. On the contrary, molting gives shrimp new vitality. By molting, the organisms attached to the original body, melanin in gills and brown spots on the body are removed, so that the shrimp can regain health and play the role of "reborn" and "rejuvenation".