REDESCRIPTION AND PHYLOGENY OF MYXOBOLUS TANAKAI KATO ET AL., 2017

This study redescribed Myxobolus tanakai Kato, et al., 2017 parasitizing the gills of Carassius auratus auratus from Jiangjin District of Chongqing based on morphological and molecular data (18S rDNA), and compared M. tanakai with other genetic related species using phylogeny. Morphologically, the spores were long pear-shaped with a posterior blunt end and a size of (14.58±0.54) μm × (6.09±0.37) μm. The two polar capsules were equal; polar filaments perpendicularly to the longitudinal axis of the polar capsules wounded eight to ten coils; a large triangle intercapsular appendix was observed in front of the two polar capsules; iodinophilous vacuoles was evident. Molecularly, three 18S rDNA sequences from three different samples were 99.3%—99.6% identical and clustered in a branch of phylogenetic tree with that of M. tanakai populations from the gills of Cyprinus carpio in Yamaguchi City, Japan. The results indicated that the present organism is the same species as M. tanakai from Japan. This is a new record for Chinese M. tanakai, and goldfish is a new host record. The comparative results of secondary structure of 18S rDNA V2, V4 and V7 revealed that intraspecific variation already existed in M. tanakai, which might contribute to host differentiation and geographical isolation. In addition, whether certain sequences reported in GenBank belong to Myxobolus koi remained to be clarified.