Ifremer, RBE-SG2M-LGPMM, Station de La Tremblade, Avenue de Mus de Loup, F-17390, La Tremblade, France.
Ifremer, ODE-LITTORAL-LERMPL, Station de la Trinité sur Mer, 12, rue des Résistants, F-56470, La Trinité sur Mer, France.
Parasit Vectors. 2018 Mar 2;11(1):119. doi: 10.1186/s13071-018-2692-0.
Microcell parasites are small intracellular protozoans mostly detected in molluscs and can be associated with mortalities. In 2010 and 2011, strong increases in mortality events were reported in different wild beds of the wedge clam Donax trunculus Linnaeus, along the Atlantic coast of France and the presence of potential pathogens, including microcells, was investigated.
Clams collected in different beds showing mortality were examined by histology. Based on histological observations, confirmatory analyses were carried out, including transmission electron microscopy (TEM) and molecular characterization.
Histological analyses revealed the presence of small protozoans similar to microcell parasites in different tissues of Donax trunculus, particularly in muscular and connective tissues. TEM examination confirmed the intracellular localization of the protozoans. Moreover, the lack of haplosporosomes and mitochondria suggested that the observed parasites belong to the genus Mikrocytos Farley, Wolf & Elston, 1988. Mikrocytos genus-specific PCR and in situ hybridization results supported the microscopic observations. Sequence fragments of the 18S rRNA gene shared 75-83% identity with the different Mikrocytos spp. described previously, including Mikrocytos mackini Farley, Wolf & Elston, 1988 and M. boweri Abbott, Meyer, Lowe, Kim & Johnson, 2014. Phylogenetic analyses confirmed that the microcell parasites observed in Donax trunculus in France belong to the genus Mikrocytos and suggest the existence of two distinct species.
Based on morphological, ultrastructural, molecular data and host information, the two microcell parasites detected in Donax trunculus belong to the genus Mikrocytos and are distinct from previously described members of this genus. This is the first report of Mikrocytos spp. found in France and infecting the clam Donax trunculus. Mikrocytos veneroïdes n. sp. was detected in different wild beds and Mikrocytos donaxi n. sp. was detected only in Audierne Bay.
微细胞寄生虫是一种小型的细胞内原生动物，主要在软体动物中发现，可能与死亡率有关。2010 年和 2011 年，法国大西洋沿岸不同的楔形蛤 Donax trunculus 养殖床报告了死亡率的大幅增加，同时调查了包括微细胞在内的潜在病原体的存在。
对显示死亡率的不同养殖床中的蛤进行组织学检查。基于组织学观察，进行了包括透射电子显微镜（TEM）和分子特征分析在内的确认分析。
组织学分析显示，在 Donax trunculus 的不同组织中存在类似于微细胞寄生虫的小型原生动物，特别是在肌肉和结缔组织中。TEM 检查证实了原生动物的细胞内定位。此外，缺乏裂殖体和线粒体表明观察到的寄生虫属于 Mikrocytos Farley、Wolf 和 Elston 1988 属。Mikrocytos 属特异性 PCR 和原位杂交结果支持了显微镜观察。18S rRNA 基因的序列片段与先前描述的不同 Mikrocytos spp. 共享 75-83%的同一性，包括 Mikrocytos mackini Farley、Wolf 和 Elston 1988 和 M. boweri Abbott、Meyer、Lowe、Kim 和 Johnson 2014。系统发育分析证实，在法国 Donax trunculus 中观察到的微细胞寄生虫属于 Mikrocytos 属，并表明存在两个不同的物种。
基于形态学、超微结构、分子数据和宿主信息，在 Donax trunculus 中检测到的两种微细胞寄生虫属于 Mikrocytos 属，与该属以前描述的成员不同。这是在法国发现的 Mikrocytos spp. 感染楔形蛤 Donax trunculus 的首次报告。在不同的野生养殖床中检测到 Mikrocytos veneroïdes n. sp.，而 Mikrocytos donaxi n. sp. 仅在 Audierne 湾检测到。
