Objective This study aims to identify the Myxobolus species infecting the gills of Acrossocheilus fasciatus.

Methods Morphological, histological and molecular analyses were undertaken to characterize this parasite.

Results It formed elliptical plasmodia in gills of fish host, with 96 μm long and 58 μm wide. Mature spores were pyriform in valvular view, measuring (11.5±0.3) μm (11.2–12.4 μm) in length and (6.1±0.3) μm (5.2–6.4 μm) in width. Two equal-sized polar capsules were pyriform, measuring (6.0±0.5) μm (5.1–6.9 μm) in length and (2.2±0.1) μm (2.0–2.5 μm) in width, each with 4–6 polar-filament coils. Comparison with all described Myxobolus spp. revealed that the present Myxobolus species did not match any known species. Histological examination showed the parasite located within the gill lamellae of A. fasciatus, with plasmodia containing spores at various developmental stages. SSU rDNA sequence analysis demonstrated that the sequence of this Myxobolus species did not match any sequence in GenBank database. The present Myxobolus species showed the highest genetic similarity to M. dykovae (EU643627) and M. tasikkenyirensis (EU643626), with sequence identities values of 94.16% and 92.60%, respectively. Phylogenetic analysis placed the present Myxobolus species in a distinct clade with other gill-parasitic Myxobolus spp.

Conclusion Consequently, this parasite infecting the gills of A. fasciatus is identified as a novel Myxobolus species, named M. jiningensis n. sp. It is the first myxosporean species reported from A. fasciatus, providing baseline data for future studies on the myxosporean parasites of this fish.