Scylla serrata ciliosis

Scylla serrata ciliosis

Etiology: the disease is caused by ciliate parasites. There are many species of ciliates parasitic on Scylla serrata, the most common of which are condensed worms, monomeric worms and cumulus. The structure of each kind of worm is roughly the same, in the shape of a bell or goblet, with a disk-shaped marginal membrane at the front end, with ciliated edges, and a handle attached to the eggs, larvae, young and adult crabs of Scylla serrata at the back end. When a large number of reproduction, it will affect the normal activities of the larvae, so that the reduction of food intake, respiratory obstruction, molting metamorphosis difficulties, serious can cause a large number of death of flea larvae. There are many fluffy things on the body surface of sick young crabs and adult crabs, which are slow in response, slow in movement and difficult to breathe. When the dissolved oxygen in the pool water is low, they often die. The disease is characterized by a long course of disease and high cumulative mortality. The main cause of the disease is that the stocking density of the pond is too high, the residual bait is too much, the pollution is serious, and the content of organic matter in the water is on the high side, resulting in extreme eutrophication of the culture pond water and the proliferation of ciliates, especially during the high temperature period from July to September every year. A large number of ciliates attached to the crab body, seriously affecting the normal growth and development of the green crab.

Symptoms: in the early stage of the disease, there are yellowish green and brown hair on the body surface, slow activity and slow response to external stimuli. The existence of ciliate protozoa such as bell worm and cumulus can be observed by microscope. In the middle and late stages of the disease, the crab body was attached by thick attachments, causing damage to the Gill filaments, dyspnea, secondary infection of bacterial diseases, loss of appetite, even no feeding, stagnation of growth and development, physical weakness and difficulty in molting, and the mortality rate was about 20-30%.