Erection of Unicapsulocaudum mugilum gen. et sp nov (Myxozoa: Ceratomyxidae) based on its morphological and molecular data

Unicapsulocaudum mugilum gen. et sp. nov. was isolated from the gallbladder of marine Mugil cephalus L., 1758 from the coast of Xiamen, East China Sea, China. Morphological studies indicated that its spores are 2.9 +/- 0.3 mu m long and 25.4 +/- 3.8 mu m thick, each with a single pyriform polar capsule (5.2 +/- 1.2 mu m long and 2.6 +/- 0.3 mu m thick) positioned inside the bulky anterior end, and containing polar filaments with two turns. The spore is distinct from that of all other known myxozoans in having an ophidian-like form with a horn-like protuberance and a long tapering tail. Molecular studies indicated that the sequence of its small subunit ribosomal DNA (SSU rDNA) does not match any myxozoans sequenced to date. Molecular phylogenetic studies based on both Bayesian and maximum likelihood methods indicated that Unicapsulocaudum mugilum sp. nov. clustered with Ceratomyxa amazonensis, Ceratomyxa tunisiensis, Ceratomyxa leatherjacketi and Myxodavisia bulani as an older evolutionary ceratomyxid lineage. Considering its morphological characters, habitat and phylogenetic relationships with other main Ceratomyxidae species, we propose the erection of a new genus Unicapsulocaudum in Ceratomyxidae.