A Novel Cystodiscus Lutz, 1889 Species (Myxozoa: Myxosporea: Bivalvulida) Isolated from Three Hynobiid Salamanders in Japan: First Record of Myxosporeans from Asian Salamanders.

BACKGROUND: Myxosporeans infecting amphibians, particularly Asian salamanders, remain poorly investigated. I conducted a parasitological survey of Japanese salamanders to investigate the occurrence of myxosporean infections.

MATERIALS AND METHODS: A parasitological survey was conducted on 132 individuals representing 27 taxa (26 species and one hybrid taxon) of Japanese salamanders belonging to three families. The parasites obtained were examined morphologically using light microscopy and scanning electron microscopy (SEM), and molecular analyses were performed using partial sequences of the small subunit (SSU) and large subunit (LSU) rDNA genes.

RESULTS: Myxosporean parasites belonging to the genus Cystodiscus were identified from the gallbladders of three hynobiid salamanders: Hynobius kimurae, H. tagoi, and H. utsunomiyaorum. Based on morphological and molecular evidence, the parasite is herein described as a new species, Cystodiscus uptoni n. sp. The species is characterized by its myxospore morphology and the presence of motile plasmodia. This represents the first record of a myxosporean infection in salamanders in Asia and the first record of the genus Cystodiscus from Japan. Molecular phylogenetic analyses supported the distinctiveness of the new species from previously sequenced congeners. Myxosporeans were not detected in the remaining 23 salamander taxa, although plasmodia-like structures lacking mature spores were observed in H. hirosei.

CONCLUSION: This study provides the first evidence of myxosporean infection in Asian salamanders and expands the known host and geographic ranges of Cystodiscus. The results highlight the need for further investigations of myxosporean diversity and host associations in Asian salamanders.