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Gills are important organs of Penaeus vannamei, mainly play a respiratory role, while the gills are an indicator organ when the shrimp is onset, many pathogens will lead to gill disease of shrimp, this is because the gills are the organs of direct contact between the shrimp body and the outside world, and its defense ability is weak, so when the pathogen is infected, the gills are often the first to be harmed and symptoms appear.
Because the gills are involved in the breathing, excretion and other physiological activities of the shrimp body, they play a very important role in the body's metabolism, and the damage to the gills will inevitably aggravate the disease and even die, which is also the cause of the greater harm to shrimp gill disease. By observing the lesions of the shrimp gills, especially the color of the gills, the incidence and cause of shrimp can be judged in a timely manner. Common gill lesions appear yellow and black in color.
The specific reasons can be divided into the following categories:
1. Bacterial infestation:
After the shrimp become ill, their feeding is reduced or stopped, and they often swim slowly at the edge of the pool without regularity, sometimes head-up and whirling on the surface of the water, easily frightened and jumping out of the water. When changing water, it is often washed by the water flow to the bottom of the sewage outlet due to lack of body. Severely ill people lose their balance and die from side pool bottom. The pathogen that causes the disease is Vibrio, of which Vibrio algae, Vibrio parahaemolyticus, and Vibrio eel are the most common.
In the early stages of the disease , the gills of the shrimp are pale yellow. As the disease progresses, the gills become more enlarged, loose, and change from yellow to yellowish brown, forming plaques; The gill tissue becomes brittle and even eroded; The body color darkens, and the inside of the carapace in the gill area turns yellow. The second tentacle whip becomes red and easy to break, there are black ulcers or dark spots on the carapace, the muscles are white and turbid, the swimming feet of some shrimp become red, and the blood clotting time is delayed. Microscopic examination can show irregular enlargement at the end of the gill filament, and vacuolar degeneration of gill tissue; There is rod-like bacterial activity inside the gill filament and in the hemolymph. It is recommended to take five yellow powder + vibrio net in the mixture for the prevention and treatment of bacterial diseases such as shrimp and crab and frog red-legged disease, fluorescent disease, blind eye disease, rotten gill disease, black gill disease, carapace ulcer disease and so on.
2. Ciliate attachment:
The diseased shrimp are sluggish and their appetite is weakened. The gill lid is slightly turned outward, the gills are swollen, and there are many fluffy light yellow objects attached to the gills, and if other debris is glued, it is often yellowish brown or black. The attachment is seen under the microscope as a large number of dense, active ciliates. Ciliates generally do not invade the shrimp body tissue, gills and other tissues, including blood are not obvious pathological changes, nor are bacteria or other organisms found. Ciliates found in the gills of diseased shrimp mainly include polycondenders, monotococcylomas and prunes, and bellworms. It is recommended to take the parasitic net inside the mixture to kill and inhibit in vivo and foreign parasites and free parasites in the water, such as oblique tube worms, wheel worms, ciliates, etc.; Products in aquaculture technical dictionary. Parasitic net is a safe and non-toxic traditional Chinese medicine raw material, with the effect of internal and external double deworming, so that the parasite gradually detaches from the fish body, while dealing with the problem of excessive gill mucus caused by parasites and swelling of gills - this is the place where parasites are most harmful. Through the role of these two aspects, the purpose of gradually restoring the health of the fish body is achieved.
3. Algae epiphytes:
When the algae are overgrown and the water in the shrimp pond is nearly sauce-colored, the shrimp will also make the gill area yellow due to the accumulation of a large number of algae (especially diatoms) in the gills. However, there were no obvious abnormalities in the active feeding of shrimp. In some new yellow mud bottom shrimp ponds, submerged species are stocked or overwintered, and yellow gills also appear in shrimp due to the subsplute on the gills.
4. Poor environment:
The black gills caused by environmental factors are physiological, with stripes of black markings in the gills of the appearance, local or diffuse necrosis of the gills on microscopic examination, and brown or black of the necrotic gills. After the aquaculture water is polluted by cadmium, copper, crude oil, etc., the water quality deteriorates, and the residual feed at the bottom of the pond is decomposed and decomposed to produce ammonia, nitrite, hydrogen sulfide and other substances, which causes chronic poisoning of shrimp and causes black gill disease; There are also cases where copper sulfate or potassium permanganate is used in excessive or excessive doses in the prevention and control of shrimp disease, copper ions directly damage the gills, or manganese dioxide formed by potassium permanganate adheres to the surface of the gills, causing black gills; In addition, due to the lack of vitamin C in shrimp, it is also easy to cause shrimp to suffer from black gill disease.
Hazards of yellow and black gills to shrimp:
1. After the shrimp disease, the feeding is reduced or stopped, and the growth is slow;
2, can not absorb the appropriate amount of water nutrients, trace elements will cause slimming, cotton shrimp, directly affect the market sales of shrimp;
3. The diseased shrimp is damaged by the respiratory function of the gills, causing the shrimp to have difficulty breathing and poisoning and lack of oxygen in the body, and the poor physique causes the occurrence of shelling and death.
Prevention and control methods of shrimp gill disease:
1, increase the time to open the aerator: to improve the content of dissolved oxygen in the pool water, because there are lesions in the gills of the shrimp, it is easy to cause hypoxia in the shrimp body, and when it encounters bad weather, it leads to a large number of deaths.
2. Change the water 15-20cm when there is a condition: then sprinkle the whole pool with the water disinfectant povidone iodine and repeat it every other day. It is best to change the water appropriately the day after disinfection.
3. The amount of quicklime once, 15 to 20 kg per acre, is regularly sprinkled throughout the pond to prevent black gill disease caused by too much organic matter in suspended matter in the water. However, when pond ammonia nitrogen NH4 is too high, especially above the standard, it is prudent to use quicklime, or a small number of times to sprinkle quicklime.
4, regular deworming and bacteriostatic: ciliate caused by shrimp gills problems, can be used parasitic net, 1 bag mixed with 120 pounds of material, and with sprinkling, 1 bag sprinkled with one meter deep water 5 acres, effective prevention and control of ciliate; At the same time, the net of Vibrio can inhibit Vibrio and inhibit the reproduction of harmful bacteria. Clinical application has proved to effectively inhibit and reproduce the growth and reproduction of pathogenic microorganisms of harmful bacteria, maintain the respiratory system and intestinal health of animals, and can be safely added for a long time, harmless and without residue.