Morphological and molecular characterizations of Myxobolus tachysurus sp. nov. (Myxozoa, Myxosporea) infecting the palate of yellow catfish Tachysurus fulvidraco in China

The Xiangjiang River, a major tributary of the Yangtze River and the largest river in Hunan Province, harbors approximately 179 fish species. As part of an ongoing survey of myxosporean diversity in this river, a new Myxobolus species infecting the yellow catfish Tachysurus fulvidraco was discovered. The new species was characterized based on morphological, histopathological, infection-related, and molecular analyses. Macroscopic whitish plasmodia were formed in the muscle layer of the palate, with no distinct inflammatory reaction observed. Morphological comparisons revealed that this species can be distinguished from morphologically similar species by differences in plasmodial size, myxospore size, and polar capsule size, as well as by infection sites and the number of polar tube coils. Phylogenetic analyses indicated that species clustered mainly according to host affinity, with few exceptions. The novel species did not cluster with Siluriformes-infecting species with pyriform myxospores within Clade D. Instead, it formed a sister clade to M. separatus , which infects the gill filaments of T. fulvidraco , and M. nagaraensis within Clade A, with moderate support values. Based on these findings, the parasite is described herein as a new species, Myxobolus tachysurus sp. nov .