碩士 / 國立臺灣海洋大學 / 水產養殖學系 / 98 / This thesis investigated the pathogenicity of Vibrio on mud crab (Scylla serrata) cultured in Taiwan together with and pathological of seuration. Scylla serrata was susceptible to Vibriosis leading to death with the symptoms including yellowing of chelating feet, whitish and erosion of muscle, abnormal in the colour (often yellowish brown) and coagulation hemolymph, erosion in hepatopancreas and so on. Bacteria were isolated from diseased Scylla serrata, with Vibrio parahaemolyticus and V. alginolyticus as the two dominant pathogenic species. In this study, virulent Vibrio parahaemolyticus (HP1) and V. alginolyticus (YH5) were selected for virulence challenge tests. The LD50 values of V. parahaemolyticus (HP1) bacteria and its extracellular products (ECP) were 2.24 × 105 CFU/g and 0.15 μg protein/g crab, respectively; and for V. alginolyticus (YH5), the LD50 values of values of bacteria and its ECP were 3.16 × 104 CFU/g and 0.42 μg protein/g crab, respectively. In the virulence tests, both of the two Vibrio species caused rapid death in the mud crab challenged with bacteria and ECP. The average time of each individual mud crab died caused by of V. alginolyticus (YH5) and its ECP were 180 minutes and 60 mins, respectively, while V. parahaemolyticus (HP1) were 140 mins and 50 mins, respectively. Similar symptoms on the mud crabs could be observed with eyestalk retraction in the beginning, followed by no response to external stimuli and individual paralysis, and some individuals with self amputation (autotomy). Erosion of the hepatopancreas was observed in most of the moribund and freshly died mud crab with no other obvious symptom.
Tissues of moribund crab after challenge with bacteria and ECP were fixed with Davidson’s solution for further histopathological
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observation. Mud crab challenged with V. alginolyticus(YH5) and V. parahaemolyticus(HP1) exhibited muscle fibres necrosis and atrophy, the presence of bacteria cluster in some tissues, and decrease of blood lymphocytes in necrotic tissues. The pathological difference between the two of bacterial strains was that abnormal material deposition visualized as bright pink could be observed only in muscle challenged with strain HP1. In the hepatopancreas, cell degeneration and necrosis of microtubules were observed, together with disappearance on blur of cell contours and the deposition of red light bacterial cells with different sizes. Necrosis of muscle fibres could be observed in crab treated with ECP of both two Vibrio strains. Visible necrosis and vacuolization of microtubules and together with loss of epithelial cells of luman, and bright pink abnormal material deposition could only be visualized in samples treated with strain HP1. This study showed that V. parahaemolyticus and V. alginolyticus were important pathogens of Scylla serrata, which could cause infection during the culture of Scylla serrata. Further studies are needed to understand the pathogenesis of these two Vibrio species in mud crab.
| Identifer | oai:union.ndltd.org:TW/098NTOU5086013 |
| Date | January 2010 |
| Creators | Chia-Wei Hung, 洪嘉偉 |
| Contributors | Ping-Chung Liu, 劉秉忠 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 86 |
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