Identification and description of Myxobolus jiningensis n. sp. infecting gills of Acrossocheilus fasciatus

Objective This study aims to identify the Myxobolus species in the gills of Acrossocheilus fasciatus, a systematic comparison was conducted using morphological, histological and molecular analysis. Methods Morphological, histological and molecular analyses were undertaken to characterize this parasite. Results It forms elliptical plasmodia in gills of fish host, with 96 μm long and 58 μm wide. Mature spores are pyriform in valvular view, measuring 11.5±0.3 (11.2-12.4) μm in length and 6.1±0.3 (5.2-6.4) μm in width. Two equal-sized polar capsules are pyriform, 6.0±0.5 (5.1-6.9) μm×2.2±0.1 (2.0-2.5) μm, 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 fish host, 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. BLAST analysis revealed the highest similarity to M. dykovae (EU643627) and M. tasikkenyirensis (EU643626), with sequence identities 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 species is identified as a novel Myxobolus species, named M. jiningensis n. sp. It is the first myxosporean reported from A. fasciatus, providing reference material for studies on the myxosporean parasites of A. fasciatus.