Myxobolus oralis sp. n. (Myxosporea: Bivalvulida) infecting the palate in the mouth of gibel carp Carassius auratus gibelio (Cypriniformes: Cyprinidae).

During a survey on the myxosporean fauna of gibel carp Carassius auratus gibelio (Bloch) in China, a species of Myxobolus Bütschli, 1882 that did not conform to any known species was found. The species is characterised by the presence of round to ellipsoidal plasmodia of 2.6-4.0 mm in diameter in the palate of host. Mature spores are obovate in frontal view and lemon-shaped in lateral view, with the following range, mean and standard deviation of dimensions: 10.8-12.8 μm (11.7 ± 0.4 μm) long, 8.2-9.9 μm (8.9 ± 0.4 μm) wide and 6.0-7.5 μm (6.8 ± 0.3 μm) thick. Two polar capsules are pyriform, 4.0-5.5 μm (4.8 ± 0.3 μm) long by 2.9-3.6 μm (3.0 ± 0.2 μm) wide. Polar filaments are coiled, with 5 to 6 turns. A small proportion of spores possesses a short caudal process. Scanning electron microscopy revealed discoid spores with a low sutural ridge and middle bulge. The small subunit ribosomal DNA sequence of this species did not match any available sequences in GenBank. Phylogenetically, this species is sister to M. nielii (Nie et Li, 1973) and M. hearti Chen, 1998 in a Henneguya-Myxobolus clade with robust support. Given the morphological and molecular differences between this species and other Myxobolus species, we propose the name Myxobolus oralis sp. n. for this parasite from gibel carp.