【作者】 雷曼红；

【导师】 汪开毓；

【作者基本信息】 四川农业大学 ， 基础兽医学， 2005， 硕士

【摘要】 本实验将40尾体重为25±2g金鱼随机分为2组,用刚孵化的多子小瓜虫幼虫直接感染金鱼,对小瓜虫形态发育及感染金鱼的动态病理学进行了研究。结果表明小瓜虫的形态发育经历成虫、胞囊及幼虫三个阶段。成虫,椭圆形或球形,大小为350～800×300～500μm,周身密被纤毛。扫描电镜下,胞口位于虫体的顶端腹面,腹缝线明显。透射电镜下,成虫纤毛轴丝微管有“9+3”的结构。虫体有大、小核各一,大核多为肾形,小核球形或三角形,位于大核的凹侧,大、小核均有核膜,胞质内含有大量线粒体、粘液泡、伸缩泡、食物泡、微管、粗面内质网等细胞器。胞囊,其大小随成虫大小变化,成虫越大,其胞囊越大;成虫形成胞囊所需的时间随水温的升高而缩短,胞囊内孵出幼虫所需的时间随温度升高而变短,囊壁厚度随水温升高而变薄。透射电镜观察,囊壁由三层组成,内、外两层电子密度高,中间层电子密度低、均质。幼虫,卵圆形,大小为30～50×24～43μm。扫描电镜下,周身纤毛排列整齐,胞口位于虫体的顶端腹面,腹缝线不明显。透射电镜下,大小核分开,其它结构和成虫相似。 水温为15～20℃时,小瓜虫幼虫在30min内钻到金鱼的体表粘液里;感染4h,幼虫完全钻入鱼体表皮,粘液分泌亢进,但体表无明显的组织病理变化;感染24h,虫体一般钻入深层表皮组织,上皮细胞增生,表皮增厚。感染96h,虫体发育成熟,虫体内有一明显的马蹄形大核,上皮组织破裂、脱落。感染216小时,鱼体表出现“小白点”,白点周围的表皮坏死。对鳃的影响很严重,鱼体对小瓜虫感染的反应只局限于感染的局部。小瓜虫寄生在鳃小片间,被鱼的上皮细胞包围起来,相邻鳃小片粘连,鳃呼吸上皮细胞增生,鳃小片水肿、扭曲、变形、断裂、结构模糊,鳃丝结构消失,毛细血管充血。寄生虫影响了鳃对气体、离子交换,最终影响鱼的新陈代谢及生存。更多还原

【Abstract】 40 goldfish (carassis auratus), initial body weight 25 ± 2g, were randomly divided into 2 groups and experimentally infected with Ichthyophthirius Multifiliis at 800 or 1000 theronts /fish following cyst incubation at 15-20 ℃ .This study included the sequence of morphological events of I. multifiliis, histopathology of experimental I. multifiliis infections in goldfish. The studies showed there were three stages of the life cycle of the parasite, the trophont stage, the cyst stage and the theront stage.Trophont, a size of 350~800×300~500mn in diameter,was ovoid or spheriform. Its cytostome was at the end of the body and the ventral sutural line was obvious. The structure of the trophont was studied by transmission electron microscopy. The cilia was ranged in a regular form and displayed the axoneme tubules to the classic morphology of "9+3 "pattern in cross section.the parasite was possessed of a macronucleus and a micronucleus.The macronucleus generally was reniform in shape,the micronucleus appeard spherical or triangular and lay closely to the concavity of the macronucleus.Both nuclei were bounded by a layer of nuclear membrane. The cytoplast of the parasite contained a large number of mucocysts, contractile vacuoles, food vacuoles, mitochondria et al. organelles. The structure of cyst wall of the free-living encysted stage of I. multifiliis was studied by transmission electron microscopy. The wall consisted of a relatively homogeneous inner layer and a somewhat more electron-dense outer layer.Cyst wall thickness was not uniform in a single cyst and thinner in warmer water.Theront, a size of 30~50×24~43μm in diameter, was ovoid. Its cytostome was at the end of the body and that the ventral sutural line was not obvious. The structure of the theront was studied by transmission electron microscopy, the theront’s macronucleus and micronucleus disjoined each other and other organelles were similar to the trophont’s.After infecting within 30min, some free-swimming theronts were present in the surface mucus of the fish. The parasite completed its invasion of the epithelial layer within 4h of exposure to the fish.There was a general increase in mucous in the integumentary epithelium.The primary infection did not induce significant histopathological changes in the integument.By 24h,most of the theronts had penetrated the host tissue to the maximum extent and begun to transform into young trophonts,causing epithelium hyperplasy. Thedistinct horseshoe-shaped nucleus of mature trophozoites was recorded at 96 h and the integumentary epithelium were necropsied. At 216h,there were whitish thickenings in the skin and necrosis of peripheral areas. The gill was the most seriously damaged organ. The response of the fish to I. multifiliis infection was limited to the surrounding epithelial cells of the fish. The presence of I. multifiUis cysted in the secondary gill lamellae, encapsulated by respiratory epithelium cells,causing adherence of adjacent lamellae, hyperplasia of epithelial cells,congestion, oedema, epithelial displacement, gill deformation and adhesions.Gill lesions resulting from parasitic infections affected gas and ion interchanging and consequently fish metabolism and living.更多还原