Freeman M A, Bell A S, Sommerville C
Institute of Aquaculture, University of Stirling, Stirling, UK.
J Fish Dis. 2003 Nov-Dec;26(11-12):667-76. doi: 10.1046/j.1365-2761.2003.00498.x.
The sea louse, Lepeophtheirus salmonis, is an obligate ectoparasitic copepod that lives on the external surface of salmonid fish. It is the most common ectoparasite of marine cage-reared salmonids, causing major economic loss to the aquaculture industry. During a sea louse monitoring programme, samples of L. salmonis were found to harbour an unreported microsporidian parasite. The microsporidian was observed in pre-adult and adult stages of both male and female copepods, with a prevalence of up to 5%. Unfixed spores were slightly pyriform in shape measuring 2.34 microm by 1.83 microm (+/- 0.01 microm) and were not observed to be enclosed by a sporophorous vesicle. The microsporidian infection was observed in all areas of the copepods' body, xenoma-like cysts forming directly under the cuticle in the epidermal tissue layer. In the present study, rDNA (530f-580r) sequence data gathered from the unidentified microsporidian parasite isolated from infected sea lice were compared with equivalents available in the databases in an attempt to identify its systematic position. The microsporidian was found to group within the phylogenetic clade containing the family Enterocytozoonidae, being most similar to members of the intranuclear genus Nucleospora. This is the first report of a hyperparasitic microsporidian infecting a caligid copepod.
海虱（Lepeophtheirus salmonis）是一种专性体外寄生桡足类动物，寄生于鲑科鱼类的体表。它是海水网箱养殖鲑科鱼类最常见的体外寄生虫，给水产养殖业造成重大经济损失。在一项海虱监测计划中，发现鲑海虱样本携带着一种未报告的微孢子虫寄生虫。在雌雄桡足类的成年前期和成年期均观察到这种微孢子虫，感染率高达5%。未固定的孢子略呈梨形，大小为2.34微米×1.83微米（±0.01微米），未观察到其被孢子囊泡包裹。在桡足类动物身体的所有部位均观察到微孢子虫感染，在表皮组织层的角质层正下方形成瘤状囊肿。在本研究中，将从受感染海虱中分离出的未鉴定微孢子虫寄生虫的rDNA（530f - 580r）序列数据与数据库中的等效数据进行比较，试图确定其系统位置。发现该微孢子虫属于包含肠胞虫科的系统发育分支，与核内孢属的成员最为相似。这是关于一种超寄生微孢子虫感染锚头鳋桡足类动物的首次报告。
