During an ongoing investigation into the myxosporean diversity of common carp in Chongqing, China, Myxobolus parakoi sp. nov. was found to infect the gill lamellae of Cyprinus carpio (Linnaeus, 1758). Both morphological and SSU rDNA data revealed that M. parakoi sp. nov. was distinct from other myxosporeans. Mature myxospores of M. parakoi sp. nov. were pyriform in the frontal view. The spores were 15.98 ± 0.78 (14.59-17.72) μm in length and 7.84 ± 0.78 (6.66-9.75) μm in width. The two polar capsules were pyriform and equal in size, exhibiting 8.72 ± 0.50 (7.76-9.92) μm in length and 3.03 ± 0.23 (2.63-3.56) μm in width. Polar filaments within the polar capsules were coiled with 11 or 12 turns. Phylogenetic analysis revealed that M. parakoi sp. nov. and Myxobolus koi (FJ710800) were clustered together, forming a sister subclade with Myxobolus tanakai. This study also implied that the morphology of the myxospores was generally correlated with their phylogenetic relationship, while such correlation was not strong or consistent.
Keywords: Coelenterata, SSU rDNA, molecular phylogeny, morphology, new species.