Henneguya doneci Schulman, 1962 was collected from the gill filaments of Carassius auratus gibelio (Bloch) in Hubei Province, China. The plasmodia located on the surface of the gill arches deformed the neighboring gill filaments. The size of the plasmodia ranged from 0.6 to 4.5 mm in diameter in different months. The myxospores in the plasmodia measured 10.1 (9.2-11.5) μm long × 8.0 (7.5-8.5) μm wide × 7.5 (7-8) μm thick, with two equal capsules at 4.7 (4-5.5) μm long × 3.3 (2.5-4) μm wide, and two caudal processes 32.7 (24-38.5) μm long, respectively. Polar filaments were coiled 5-6 turns. Ultrastructural observation of the plasmodia showing the capsulogenesis of H. doneci is described briefly. The external tubule initially invaginated into the polar capsule. The rudimentary polar filaments were observed to undergo a series of considerable modification, finally developing into mature polar filaments. Molecular analysis demonstrated that although the myxosporean species were collected from different tissues of hosts in various geographic locations, they clustered with the Cyprinidae-infecting myxosporean species in the phylogenetic tree.