Abstract
Myxobolus tsangwuensis Chen, 1954 is a common parasite infecting the gills of common carp Cyprinus carpio (L.). It was described simply in the original description and its molecular data was absent, which makes the accurate diagnosis challenging. Here we supplemented its description based on the morphological, histological and molecular data. It was characterized by the presence of small round or ellipsoidal plasmodia in the gills of host and histology showed the plasmodia developed in the capillary network of the gill lamella. Mature spores of M. tsangwuensis were ellipsodal in frontal view and lemon shaped in lateral view, averaging 11.2 ± 0.7 (10.2–12.5) μm × 9.3 ± 0.3 (8.5–10.0) μm × 6.2 ± 0.4 (5.5–7.0) μm. Spores valves were symmetrical and smooth. Occasionally, a small intercapsular appendix was observed. Two polar capsules were pyriform with different sizes, measuring 5.0 ± 0.2 (4.4–5.3) μm × 3.1 ± 0.1 (2.9–3.5) μm and 3.9 ± 0.2 (3.4–4.3) μm × 2.5 ± 0.2 (2.0–2.8) μm, respectively. Polar filaments coiled five to seven turns in large polar capsule and three to four turns in the small polar capsule. Some spores were surrounded by the mucous envelope that was not recorded in the original description. Molecular analysis revealed that the present SSU rDNA sequences did not match any available sequences in GenBank and phylogenetic analysis showed M. tsangwuensis was sister to M. basilamellaris and M. musseliusae.