Miamiensis avidus is a parasitic pathogen that causes the disease scuticociliatosis in teleost fish species. It is a ciliate and a free-living marine protozoan belonging to the order Philasterida, subclass Scuticociliatida, class Oligohymenophorea, and phylum Ciliophora. The complete mt-genome of M. avidus was linear and 38,695 bp in length with 47 genes, including 40 protein-coding genes, two ribosomal RNA (rRNA) genes, and five transfer RNA (tRNA) genes. Of these, 20 genes typically belong to the clusters of orthologous groups, playing roles in energy production and conversion, translation, ribosomal structure and biogenesis, and defense mechanisms. This is the first report of sequencing and characterization of the mt-genome of M. avidus, which was observed to be linear and possessing the typical ciliate mitochondrial genome organization and phylogenetic relationships. Remarkable differences were observed between M. avidus and other ciliates in the mitochondrially encoded rRNAs, extensive gene loss in ribosomal genes and tRNAs, terminal repeat sequences, and stop codon usage. A comparative and phylogenetic analysis of M. avidus and Uronema marinum of the order Hymenostomatida, which is most closely related to the order Philasterida, signified the promise of the mitogenome data of M. avidus as a valuable genetic marker in species detection and taxonomic research. The present study has potential applications in epidemiological studies and host-parasite interaction investigations facilitating disease control.

amiamiensis avidus是一种寄生病原体，可引起硬骨鱼种的盾纤毛病。它是一种纤毛虫和自由生活的海洋原生动物，属于 Philasterida 目、Scuticociliatida 亚纲、Oligohymenophorea 纲和纤毛门 (Ciliophora)。M. avidus完整的mt基因组是线性的，长度为38,695 bp，包含47个基因，其中包括40个蛋白质编码基因、2个核糖体RNA（rRNA）基因和5个转移RNA（tRNA）基因。其中，20 个基因通常属于直系同源群簇，在能量产生和转换、翻译、核糖体结构和生物发生以及防御机制中发挥作用。这是首次对M. avidus的 mt 基因组进行测序和表征，观察到该基因组是线性的，并且具有典型的纤毛虫线粒体基因组组织和系统发育关系。在线粒体编码的 rRNA、核糖体基因和 tRNA、末端重复序列和终止密码子使用方面观察到广泛的基因丢失，M. avidus和其他纤毛虫之间存在显着差异。对M. avidus和膜口目Uronema marinum（与Philasterida 目关系最密切）的比较和系统发育分析表明， M. avidus的丝裂基因组数据有望成为物种检测和分类学研究中有价值的遗传标记。本研究在流行病学研究和促进疾病控制的宿主-寄生虫相互作用研究中具有潜在的应用。