A new myxozoan, Ceratomyxa bohari sp. n., infecting the gall bladder of two-spot red snapper, Lutjanus bohar Forsskål, in the Red Sea off Saudi Arabia, is described using light microscopy and characterised genetically. The infection was recorded as mature spores floating free in the bile. The overall prevalence of infection of the type host was 19% (67 fish infected of 360 examined), with the highest prevalence in autumn (31%; 28/90) and the lowest in winter at 12% (11/90). Mature spores are slender and slightly crescent-shaped in the frontal view, with anterior and posterior margins tapered gradually to rounded valvular tips. Spore valves are unequal with a prominent sutural line. The spore dimensions are 3-4 μm (mean 3.5 μm) in length and 16-19 μm (mean 17 μm) in thickness. Two polar capsules are spherical, equal in size, 1.5 μm in diameter. Coils of the polar filament are indiscernible. The sporoplasm is binucleated and fills nearly one third of the extracapsular space restricted to the area below the capsules. The molecular analysis based on the small subunit rDNA (SSU rDNA) sequence revealed a close relationship with majority of species of Ceratomyxa Thélohan, 1892 and phylogenetic clustering with species from different geographical location. Thus, the shorter spore of the present Ceratomyxa species and the divergence of the SSU rDNA sequences were the distinctive features that separate it from all previously described species and identified this parasite as a new species of Ceratomyxa., Lamjed Mansour, Abdel-Azeem S. Abdel-Baki, Ahmad F. Tamihi, Saleh Al-Quraishy., and Obsahuje bibliografii