Cyclopsomyces plurioperculatus: a new genus and species of Lobulomycetales (Chytridiomycota, Chytridiomycetes) from Japan.

Lobulomycetales is one of the smallest orders of Chytridiomycota, containing only four genera and five species. In a survey in Japan we isolated a chytrid from a soil sample collected in a broadleaf forest, which grouped in Lobulomycetales by BLAST query. To identify this chytrid and determine its taxonomic position, thallus development and morphology were observed by light microscopy and zoospore ultrastructure was examined using a transmission electron microscopy. We conducted a phylogenetic analysis using nuc 28S rDNA sequences. Thallus morphology was characterized by a spherical zoosporangium with multiple operculate discharge papillae, which is different from that of any other species in Lobulomycetales. This chytrid is similar to Chytriomyces multioperculatus in having multiple operculate discharge papillae, but these are distinguished by characters of the discharge papillae and rhizoidal systems. Zoospores of this chytrid had electron-dense material in the kinetosome, a unique character in the order. Our 28S phylogeny placed it in a distinct clade, sister to all described species in Lobulomycetaceae. Based on these results, we propose a new genus and species of Lobulomycetales, Cyclopsomyces plurioperculatus.