Morphological and molecular characterisation of two closely related species: Myxobolus tihanyensis n. sp. and Myxobolus sandrae Reuss, 1906

Based on spore morphology and small subunit ribosomal DNA sequences, we describe a new Myxobolus species, Myxobolus tihanyensis n. sp., parasitizing the European perch (Perca fluviatilis) from Lake Balaton in Hungary. The brownish plasmodia were found in various locations of the body, mainly in the muscle adjacent with fins and vertebrae. The spores were ovoid, and measured 9.84 +/- 0.38 mu m in length, 7.69 +/- 0.23 mu m in width, and 5.35 +/- 0.21 mu m in thickness, with 8-10 sutural (edge) markings. The polar capsules were mostly equal in size, with 4.91 +/- 0.39 mu m in length and 2.27 +/- 0.24 mu m in width. The polar tubule length is 38.15 mu m +/- 2.70, and coiled 6-7 times. In particular, these morphological data overlap with those of Myxobolus sandrae Reuss1906 infecting the European perch (Perca fluviatilis), the pikeperch (Sander lucioperca), and the Volga pikeperch (Sander volgensis) according to previous descriptions and the taxonomic data here described. However, the phylogenetic analyses separate the two species as sister clades with 16.8% genetic distance. This study has demonstrated that the two species of Myxobolus exhibit phenotypic similarity while displaying significant genetic divergence. Therefore, the importance of including molecular data in the taxonomic description of myxozoans is emphasized.