The temperature is unstable in August, so for aquaculture, it is necessary to guard against the occurrence of many parasitic diseases. Today we are going to talk about a parasitic disease that occurs in fish, shrimp and crab farming, and the incidence cycle is long. The high incidence of the disease is from July to November of each year. River crabs and shrimp, in particular, can occur at all stages of growth.
To know how to prevent and control aquatic animal fiber diseases, we must first have a detailed and comprehensive understanding and understanding of this disease. It has been found that ciliate disease in aquatic animals is mainly caused by ciliate parasitism such as polycontoles, twigs, and bellworms.
Solid ciliates belong to the ciliate species, there are many species, these different species of insect body structure is roughly the same, in the shape of an inverted bell cover or goblet shape, the front end of the formation of a disc-shaped mouth disc, the edge of the cilia, there is a groove inside; the worm body has a band,horseshoe-shaped, oval large nucleus 1 and 1 small nucleus, the posterior end of the worm body has a stalk or no sessile. The type of stalk is distinguished according to whether the stalk is branched (monomer or group), whether there is muscle filament in the stalk, whether the muscle filament is connected at the branch (the connected group is synchronously expanded, and the individual is stretched separately if it is not connected), and the muscle filament is arranged axially, Z-shaped when contracted, or the muscle filament is coiled along the inner wall of the stalk, and spiraled when contracted. Asexual reproduction is a longitudinal dichotomy, and sexual reproduction is unequal joint reproduction.
Solid ciliates feed on bacteria or organic detritus, do not directly invade the organs or tissues of the host, and only use the surface of the host and gills as a base for life, so they belong to symbiotic organisms. They coexist in various periods of the life history of shrimp, when the number of cohabitations is not large, the naked eye can not see the symptoms, the harm is not serious, in the host molting with it, but when the number is large, the harm is very serious.
The distribution of solid ciliates is worldwide, and it often occurs in shrimp and crab farms and nurseries in various coastal areas of China. In particular, it is seriously harmful to juveniles. The main pathogens during the nursery period are bell worms and polyconcretes, while during the grow-out period they are mainly polymers. The disease is most likely to occur in organically rich water. In shrimp and crab breeding ponds, the occurrence of this disease is mainly caused by conditions such as more sludge at the bottom of the pond, excessive amount of bait, excessive stocking density, dirty water quality, and poor water exchange.
1. Ciliates can parasitize shrimp, sludge, etc. attached to ciliates, and the hands feel like a layer of slippery oil.
2. When the shrimp is severely parasitic, the shrimp is full of ciliates, the mouthparts cannot open their mouths, the eyes cannot be retracted and rotated, the movement is slow, and the response to external stimuli becomes slower.
3. There is dirt hanging on the cheeks and increased mucus, difficulty breathing, damage to gills, decreased system, secondary infection with bacteria or viruses, resulting in decreased appetite of shrimp, or even non-feeding.
4. When a large number of ciliates parasitize shrimp, it will hinder the dehulling of shrimp and make it difficult to dehull and affect the growth of shrimp.
5. They are attached to the body surface of shrimp and crabs, the carapace of the appendages and the gills of adults, and when a large number of epigenetics are born on the surface of the body, the naked eye sees a layer of gray-black fluff.
6, in the larva often appear in the base of the cephalothorax appendage and the tail of the larvae, in the adult shrimp is often appeared on the gills and the appendages of the cephalothorax, infected shrimp, gill filaments are covered with insect bodies, and often with filamentous bacteria and other protozoa at the same time, between the insect body also adhere to some single-celled algae, organic debris and dirt, etc., the naked eye looks gills blackened, so some people also call black gills.
7. When examined under the microscope, it is found that the tissue of the gills themselves does not turn black. The appearance of blackening is the color of insect bodies and dirt. These insect bodies and dirt hinder the flow of water between the gills and the exchange of gases on the gill surface, reducing the shrimp's tolerance to hypoxia and making it easy to suffocate and die.
8. Diseased adult shrimp or larvae, swimming slowly, reducing feeding ability, growth and development stopped, can not molt, it will further promote the attachment and proliferation of solid ciliates, the result will cause a large number of death of the host.
1, environmental factors, when the residual bait feces bottom organic matter increases, the bottom deteriorates, the large number of harmful bacteria for the large number of ciliates to provide a good environment.
2. Institutional factors of aquatic animals themselves: especially shrimp are stressed many times, and when the system is weak, slow movement is easy to lie on the bottom, resulting in parasitic attachment of ciliates.
1, in the breeding process, first of all, we must pay attention to maintaining the salinity, temperature and transparency of the water. To maintain the stability and balance of the water quality environment, do not have major changes, it is necessary to regularly measure the water quality indicators and take oxygenation measures to keep the dissolved oxygen of the pool water not less than 5 mg / l.
2, the brine eggs fed during the fry stage should be disinfected, which can be disinfected with 300 grams of bleach powder per cubic meter of water or 300-500 ml of formalin for 1 hour, and can also be soaked in 60-70 degrees of hot water for about 5 minutes, killing ciliates and then feeding.
3, in the process of breeding, we must regularly clean the fish pond, timely clean, keep the entire water environment clean and sanitary, and disinfect the fish pond once every half a month, you can use iodine-containing disinfectant to prevent farmed fish from being infected with ciliate disease.
4. Change the water appropriately, throw the bait reasonably, feed the fresh feed, and improve the disease resistance of the fish body through daily feeding and management.
It should be noted that the concentration of disinfectant used should not be too high, and at the same time, it is necessary to check and diagnose whether the fish have bacterial or viral infections in time, and if the fish is found to be wrong, the fish disease should be treated in time to prevent the decline of physical fitness from inducing ciliate disease.
If the number of combid ciliates is not large, there is no need to treat, as long as the above precautions to promote the growth and development of shrimp and crabs and molting will be naturally healed; if the number of solid ciliates is large, it should be treated in time, and the following points are also to be done:
2. Adult shrimp pond can be sprinkled with 0.5 mg/l copper sulfate to promote molting. Nursery ponds can be temporarily warmed by 2-3 degrees to promote molting and then water change.
3. For the shrimp and crab larvae with disease, there is no ideal treatment method except to promote larval molting by improving the bait, increasing the amount of water exchange, and adjusting the appropriate water temperature.
4. Treatment of diseases in the grow-up stage: tea meal (tea seed cake) can be sprinkled in the whole pool, and the concentration is 10~15mg/L. Tea meal contains saponins, which promote the molting of shrimp and crabs. After the shrimp and crab molt, change the water in large quantities.
5, 25 ml / cubic meter formalin solution sprinkled in the whole pool, a large number of water changes within 24h, the remaining liquid medicine is discharged. (This article is edited and arranged by Zheng Lu of China Aquaculture Network)