Morphological, Molecular and Phylogenetic Characterization of Ceratomyxa nemiptera sp. nov. (Myxozoa: Ceratomyxidae) Infecting Nemipterus virgatus Houttuyn, 1782 in the East China Sea

A newly discovered myxosporean parasite was described from the gallbladder of <i>Nemipterus virgatus</i> Houttuyn, 1782 collected from the East China Sea. Mature myxospores are crescent-shaped with shell valves that taper gradually toward rounded ends. Each myxospore contained two sub-spherical polar capsules located near the anterior end, closely aligned along the suture line. The mature myxospores measured 6.2 ± 0.6 (5.4-6.9) μm in length and 44.8 ± 4.6 (38.5-53.1) μm in thickness. Polar capsules measured 2.8 ± 0.2 (2.4-3.1) μm in length and 2.3 ± 0.2 (1.9-2.6) μm in width, with polar filaments coiled in 2-3 turns. The small subunit ribosomal DNA (SSU rDNA) sequence of <i>Ceratomyxa nemiptera</i> sp. nov. was distinct from all known myxosporeans, showing the highest similarity (93.56%) and the shortest genetic distance (0.0637) with <i>Ceratomyxa arcuata</i> Thélohan, 1892. The phylogenetic analysis revealed that <i>C. nemiptera</i> sp. nov. was positioned within a later-diverging lineage, forming a sister-group relationship with a clade containing <i>C. arcuata</i> and <i>Ceratomyxa cretensis</i> Kalatzis, Kokkari & Katharios, 2013. This is the first report of a <i>Ceratomyxa</i> species infecting <i>N. virgatus</i>.