AbstractAMyxobolusspecies and aThelohanellusspecies infectingCarassius auratus gibelio(Bloch, 1782) were redescribed by their morphological, histological and molecular characterization. In the present study, theMyxobolusspecies infecting the muscle was identified asMyxobolus kingchowensisChen et Ma, 1998 by the morphological and molecular data. Histologically, mature spores ofM.kingchowensiswere observed in the intercellular and connective tissue of muscle, though the plasmodia were not found. In addition, scattered spores also occurred in the intercellular of haematopoietic cells, intraepithelial of the renal tubules and interior of the melano-macrophage centres. Phylogenetic analysis showed thatM.kingchowensisclustered in the clade of muscle-infectingMyxobolusspecies, further supporting muscle as the infection site ofM.kingchowensis. The presentThelohanellusspecies infecting the gills was identified conspecific asThelohanellus sinensisreported in Sun (2006) (mark it asT.sinensis-Sun)based on spore morphology, biological traits (host specificity and organ specificity), and molecular data. However, compared with the original description ofT.sinensisChen et Hsieh, 1960, the presentThelohanellusspecies andT.sinensis-Sun both infecting the gills of gibel carp are distinguishable from the original description in the host and infection site, which made the validity ofT.sinensis-Sun dubious. Due to the absence of molecular data in the original description ofT. sinensis, we suggest marking the present species andT.sinensis-Sun asT. cf.sinensisto avoid the confusion untilT.sinensisis obtained from the type host and type infection site.
