| This article researches chronic gas bubble disease of largemouth bass undernatural condition by etiology analysis and histopathology observation. Then simulatethe occurrence condition of this disease in the laboratory, according to the degree ofsupersaturation which led to chronic gas bubble disease under natural condition, toestablish a disease model of chronic gas bubble disease of largemouth bass. Thenresearch chronic gas bubble disease of largemouth bass under experimental conditionby etiology analysis and histopathology observation, contrast to the former researchunder natural condition, provide the scientific basis to diagnosis and precaution of thisdisease of largemouth bass.1. To investigate the degree of supersaturated oxygen of water in ponds undernatural condition, find that water supersaturated with oxygen is quite common inponds which breeding largemouth bass in Shunde district of Guangdong province, andstratification of water body in these ponds is quite common too. Due to the differentweather, the different condition of the pond, and the different supervisor mode of thepond, the degree of supersaturated oxygen of the superficial water and the bottomwater can be very different at the same position in the same pond, and at the sametime. Sometimes fish in ponds which degree of supersaturated oxygen of thesuperficial water were quite high, but no fish occur gas bubble disease, contrarily, fishin ponds that degree of supersaturated oxygen of the superficial water were lower, itoccurs gas bubble disease. Further study on this problem, investigate that it is easierfor Largemouth bass to get sick with chronic gas bubble disease in the pool wherewater stratified more clearly than the ones do not with similar condition of averagevalue of dissolved oxygen. So the monitoring of the degree of supersaturated oxygenof the bottom water of the pond was surgusted. 2. Simulate the pools where we did survey before with similaroxygen-dissolved situations, put100Largemouth bass which are around50g intosimulated environments with different oxygen-dissolve conditions for20-daybreeding (Saturation percentage of dissolved oxygen are50%~100%,100%~150%,150%~200%and200%~250%). Clinical examination and histopathologicalobservation on the Largemouth bass which got sick in simulated surroundings showedthat, the main symptoms of tested Largemouth are exophthalmos and opaque of thecornea, gas appeared in gill filaments, posterior eye globe and fin ray.Histopathological changes showed like retina separates from choroid, retinal pigmenthypertrophy and hyperplasia, then necrosis and disappeared, large quantity of bubblesproduced from choroid plexus, cornea vascularized, the quantity of immatureerythrocyte increased, and the composure of hemosiderin after fracture of erythrocyte.And it occurs spaces filled with bubbles in choroid plexus, vacuolation of corneaepithelium and vascularization of cornea. There were no blood cells or few blood cellsin hepatic vein, red blood cells fewer than normal individuals, the quantity ofimmature erythrocyte increased and the composure of hemosiderin after fracture oferythrocyte which lead to the infiltration of inflammatory cells. There were few bloodcells in kidney too, serious vacuolization of epithelial cells on kidney tubules,glomeruli separated from the basement membrane, disappearance of cytoarchitectureof the nephridial tubules, and composure of hemosiderin which led to infiltration ofiymphocyte in kidney. Spaces filled with bubbles in serosa, microvillus andmuscularis of intestines, and in the gills. few blood cells in gill vein, epithelial cells inthe lamellae damaged, and serious hyperplasia of stratified epithelial of some gills.3. Research chronic gas bubble disease of largemouth bass under naturalcondition by histopathology observation, then compared with ones that under artificialcondition. The result reveals that pathological change of largemouth bass undernatural condition is similar to that under artificial condition. Largemouth bass underboth conditions show pathological changes of choroid isolated from the retina, retinalpigment hypertrophy and hyperplasia, then necrosis and disappeared, large quantity ofbubbles produced from choroid plexus, and cornea vascularized, vacuolation of hepatocyte, tabular epithelial cells, microvillus and stratified epithelial cells of gillfilament, and the quantity of immature erythrocyte increased and the composure ofhemosiderin after fracture of erythrocyte which lead to the infiltration ofinflammatory cells. Proportion of immature erythrocyte of largemouth bass undernatural condition lower than that under artificial condition. It occurs extrapathological changes like mild fatty liver under natural condition, which have notoccurred under artificial condition. These may be have something to do with differentduration of exposure under supersaturated oxygen or different feeding moods underthese two conditions. |
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