Morphology, seasonality and phylogenetic relationships of Ceratomyxa husseini n. sp. from the gall-bladder of Cephalopholis hemistiktos (Rüppell) (Perciformes: Serranidae) in the Arabian Gulf off Saudi Arabia.

During a survey of myxosporean parasites of marine fishes from the Arabian Gulf in Saudi Arabia, spores of Ceratomyxa husseini n. sp. were found in the gall-bladders of 50 out of 148 specimens (33.8%) of the yellowfin hind Cephalopholis hemistiktos (Rüppell) (Perciformes: Serranidae). The rates of infection showed a seasonal fluctuation, with the highest prevalence in winter and the lowest in autumn. The mature spores appeared arched in frontal view with rounded valve ends and a slightly discriminated curved suture line and measured 8-9 × 14-18 (9 × 16) μm. The two polar capsules were spherical and equal in size, 4-5 (4.5) μm in diameter. The polar filament showed four turns obliquely to the longitudinal axis of the capsules and the sporoplasm filled half of the entire spore cavity. Partial sequences of the small subunit rRNA gene of C. husseini n. sp. showed percentage of identity with other species of Ceratomyxa ranging between 79.8 and 92.7%. The morphometric and molecular data, in association, confirmed that the present new species differs from all other Ceratomyxa spp. reported to date.