寄生部位分化对吉陶单极虫种群分化的影响  

The impacts of infection site differentiation on population divergence of Thelohanellus kitauei(Myxozoa:Myxosporea)

作　　者：沈宇航 张波[1,2,3,4] 涂笑 顾泽茂[1,2,3,4] SHEN Yuhang;ZHANG Bo;TU Xiao;GU Zemao(College of Fisheries,Huazhong Agricultural University,Wuhan 430070,China;Hubei Engineering Technology Research Center for Aquatic Animal Diseases Control and Prevention,Wuhan 430070,China;Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt,Ministry of Education,Wuhan 430070,China;National Aquatic Animal Diseases Para-reference Laboratory(HZAU),Wuhan 430070,China)

机构地区：[1]华中农业大学水产学院,湖北武汉430070 [2]湖北省水生动物病害防控工程技术研究中心,湖北武汉430070 [3]长江经济带大宗水生生物产业绿色发展教育部工程研究中心,湖北武汉430070 [4]农业农村部水生动物疫病专业实验室(华中农业大学),湖北武汉430070

出　　处：《中国水产科学》2023年第7期921-932,共12页Journal of Fishery Sciences of China

基　　金：国家自然科学基金项目(32070431);现代农业产业技术体系专项(CARS-46);湖北省农业科技创新中心项目(2021-620-000-001-33)。

摘　　要：为探究寄生部位分化对黏孢子虫种群分化的影响,以吉陶单极虫(Thelohanellus kitauei)为例,研究了寄生于鲤(Cyprinus carpio)皮肤和肠道的吉陶单极虫的形态、寄生特征和分子遗传信息。寄生皮肤的吉陶单极虫(S型)形成单个明显孢囊,直径约2.1 cm,寄生肠道的吉陶单极虫(I型)形成多个(16个)孢囊,直径0.21~0.82 cm;孢子形态特征相比,S型和I型孢子鞘膜宽差异不显著(P>0.05),但孢子厚差异显著(P<0.01),孢子长、极囊长、鞘膜长、孢子宽和极囊宽呈现极显著差异(P<0.001);组织病理结果显示,二者均寄生于结缔组织中,引起淋巴细胞浸润、组织增生等炎症反应,但S型孢子主要分散在真皮疏松层,部分孢子侵入致密层,造成结缔组织弯曲、变形,而I型孢子主要分散在肠黏膜下层上方,挤压并导致肠绒毛萎缩;分子序列比对发现,S型和I型的SSUrDNA序列相似度较高,为99.7%,具有4个差异位点,ITS-5.8S rDNA序列间相似度较低,仅97.3%,共有20个差异位点。基于SSU rDNA和ITS-5.8S rDNA序列构建的系统进化树显示,S型和I型于吉陶单极虫支系内部各自聚类,表明相同寄生部位的吉陶单极虫具有更近的亲缘关系。综上所述,寄生不同部位的吉陶单极虫在形态、寄生特征和遗传信息方面存在不同程度的差异,具有明显的种群分化特征,说明寄生部位分化是驱动黏孢子虫种群分化的重要因素。Myxosporeans are a group of microscopic parasites that primarily parasitize fish with more than 2600 species currently discovered worldwide.The rich diversity of this group has led to extensive research on population divergence in myxosporeans.To investigate the impacts of infection site differentiation on the population divergence of myxosporeans,Thelohanellus kitauei Egusa&Nakajima,1981 was isolated from the skin(S-type)and intestine(I-type)of different common carps Cyprinus carpio L.We compared the morphological differences in the T.kitauei found at the two infection sites by measuring the morphological characteristics of both plasmodia and spores.Tissue samples from the infected skin and intestine were examined by histopathology.The small subunit(SSU)ribosomal DNA(rDNA)and internal transcribed spacer(ITS)-5.8S rDNA sequences of two isolates were also amplified,aligned,and phylogenetically analyzed with other T.kitauei sequences from GenBank.The results showed that the S-type formed a single plasmodium with a diameter of 2.1 cm,while the I-type formed sixteen plasmodia of different sizes(diameters of 0.21-0.82 cm).The membrane sheath widths of the S-and I-types were approximately identical(P>0.05).However,the spore lengths,polar capsule,and membrane sheath of the S-type were significantly greater than those of the I-type(P<0.001),while other morphological characteristics were significantly smaller than those of the I-type(spore thickness:P<0.01;the width of spore and polar capsule:P<0.001).Histologically,most of the S-type spores were distributed in the stratum spongiosum of the dermis,with some spores penetrating the stratum compactum,causing curvature and deformation of the dense connective tissue.The I-type spores were primarily scattered over the intestinal submucosa,and the intestinal villi squeezed by the spores showed atrophy to varying degrees.Both types infected the connective tissue,causing inflammatory reactions such as lymphocyte infiltration and tissue hyperplasia.Molecular sequence comparison sho

关 键 词：种群分化 吉陶单极虫 寄生部位 形态比较 组织向性 核糖体DNA 

分 类 号：S941[农业科学—水产养殖]