Karlsbakk Egil, Nystøyl Cecilie Flatnes, Plarre Heidrun, Nylund Are
Department of Biological Sciences, University of Bergen, PO Box 7803, 5020, Bergen, Norway.
, Skodje, Norway.
Parasit Vectors. 2021 Aug 28;14(1):431. doi: 10.1186/s13071-021-04886-0.
In Norway, x-cell parasites associated with disease in farmed salmonids have been known as a rare phenomenon for two decades. These parasites cause systemic infections in farmed rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), but have so far not been characterized and described.
The x-cells from several cases of diseased fish were studied using light and electron microscopy, and by phylogenetic analysis based on small subunit ribosomal RNA (SSU rRNA) gene sequences.
We describe here the x-cell parasite as a new species in a new genus, Salmoxcellia vastator n. gen., n. sp. Phylogenetic analyses placed Salmoxcellia n. gen. together with Gadixcellia among the xcelliids, a group of perkinsozoan alveolates. The new genus and species were found to have vacuolate plasmodial x-cells filled with lipid droplets, and an electron-dense alveolar pellicle. Electron-dense cytoplasmic inclusions, which are characteristic of the other xcelliid genera Xcellia and Gadixcellia, are lacking in Salmoxcellia n. gen. These x-cell plasmodia divide by plasmotomy and occur as aggregates in the host tissues, particularly in blood-rich tissues such as those of the kidney, red musculature, heart and liver. Host reaction and the refractive lipid droplets in the x-cells result in S. vastator n. gen., n. sp. aggregates appearing as white patches in the tissues.
We describe a new genus and species of xcelliid protist parasites from two very important farmed fish species and provide molecular methods for detection. The new parasite is associated with disease, but more importantly it has a spoiling effect on farmed salmonid fillets, rendering them unsuitable for sale. Consequently, this parasite represents a threat to the aquaculture industry.
在挪威，与养殖鲑科鱼类疾病相关的x细胞寄生虫在二十年来一直是一种罕见现象。这些寄生虫会在养殖的虹鳟（Oncorhynchus mykiss）和大西洋鲑（Salmo salar）中引发全身性感染，但迄今为止尚未得到鉴定和描述。
利用光学显微镜和电子显微镜，以及基于小亚基核糖体RNA（SSU rRNA）基因序列的系统发育分析，对几例患病鱼类的x细胞进行了研究。
我们在此将x细胞寄生虫描述为一个新属中的新物种，即毁灭鲑x细胞虫（Salmoxcellia vastator），新属，新种。系统发育分析将鲑x细胞虫属与加迪x细胞虫属一同归入x细胞虫类，这是一类珀金氏虫纲的肺泡虫。发现这个新属和新种具有充满脂滴的泡状多核体x细胞，以及电子致密的肺泡薄膜。鲑x细胞虫属缺乏电子致密的细胞质内含物，而这是其他x细胞虫属（Xcellia和Gadixcellia）的特征。这些x细胞多核体通过质裂进行分裂，并以聚集体的形式出现在宿主组织中，特别是在富含血液的组织中，如肾脏、红色肌肉组织、心脏和肝脏。宿主反应以及x细胞中的折射性脂滴导致毁灭鲑x细胞虫聚集体在组织中呈现为白色斑块。
我们描述了一种来自两种非常重要的养殖鱼类的新属新种x细胞虫原生动物寄生虫，并提供了检测的分子方法。这种新寄生虫与疾病相关，但更重要的是，它对养殖鲑科鱼类鱼片有破坏作用，使其不适于销售。因此，这种寄生虫对水产养殖业构成了威胁。
