In the present study, we described a novel myxosporean species, Myxobolus jialingensis n. sp. (Myxozoa: Myxobolidae), which infected the urinary bladder and hepatopancreas of yellowhead catfish Tachysurus fulvidraco in China. The mature spores of M. jialingensis n. sp. were pyriform with the length of 15.8 ± 0.7 (15.4–17.0) μm and width of 8.0 ± 0.3 (7.8–8.9) μm. Two pyriform polar capsules were slightly unequal in size: the larger polar capsule was 7.4 ± 0.3 (6.7–8.0) μm in length and 3.1 ± 0.2 (2.8–3.6) μm in width; and the smaller polar capsule measured 7.3 ± 0.3 (6.6–8.1) μm in length and 3.3 ± 0.2 (2.9–3.6) μm in width. The polar capsules were directed toward the apex of the spore, packing seven to eight spirals of the polar filaments. The small subunit ribosomal RNA gene (18S rDNA) sequence of M. jialingensis n. sp. was unique among all myxozoans, and the highest similarity was 96.1% with M. voremkhai. Phylogenetic analysis based on 18S rDNA sequences revealed that myxosporeans infecting the close host affinity (belonging to the same order) had close phylogenetic relationship and, some myxosporeans infecting the same host order might have multiple origins.

Introduction Ceratomyxa Thélohan, 1892 is one of the largest genera under Myxosporea Butschli, 1881, and has a worldwide distribution, but little attention has been paid to myxosporean parasites from...

During an ongoing investigation into the myxosporean diversity of common carp in Chongqing, China, Myxobolus parakoi sp. nov. was found to infect the gill lamellae of Cyprinus carpio (Linnaeus, 1758). Both morphological and SSU rDNA data revealed that M. parakoi sp. nov. was distinct from other myxosporeans. Mature myxospores of M. parakoi sp. nov. were pyriform in the frontal view. The spores were 15.98 ± 0.78 (14.59–17.72) μm in length and 7.84 ± 0.78 (6.66–9.75) μm in width. The two polar capsules were pyriform and equal in size, exhibiting 8.72 ± 0.50 (7.76–9.92) μm in length and 3.03 ± 0.23 (2.63–3.56) μm in width. Polar filaments within the polar capsules were coiled with 11 or 12 turns. Phylogenetic analysis revealed that M. parakoi sp. nov. and Myxobolus koi (FJ710800) were clustered together, forming a sister subclade with Myxobolus tanakai. This study also implied that the morphology of the myxospores was generally correlated with their phylogenetic relationship, while such correlation was not strong or consistent.

Forest musk deer (Moschus berezovskii Flerov), a critically endangered ruminant species, faces extinction risks, with captive populations further threatened by prevalent digestive and immune disorders. This study utilized comparative metagenomic sequencing to assess intestinal microbiota structure and functional profiles between wild populations in Chongqing and Hunan and captive individuals. Wild populations exhibited a Pseudomonadota-dominated gut microbiota (significantly more abundant than in captive counterparts), enriched with lignin-degrading genera Novosphingobium and Acinetobacter. In contrast, the captive group demonstrated increased abundances of Bacillota/Bacteroidota, alongside abnormal proliferation of Escherichia and Clostridium. Both alpha and beta diversity analyses confirmed significant compositional divergences among the three groups, with wild populations maintaining higher diversity than captive populations. Notably, while substantial disparities in microbial abundance existed between wild populations (attributed to habitat vegetation differences), core microbial diversity and carbohydrate metabolic functions exhibited convergence. Functional analyses marked divergences in metabolic pathways: Captive microbiota showed enrichment in translation and glycan metabolism pathways, whereas wild populations displayed pronounced enrichment in immune regulation and environmental sensing pathways. These findings establish a theoretical foundation for optimizing wild population conservation strategies and developing science-based captive management protocols.

Two species of Ceratomyxa (Myxozoa: Ceratomyxidae) from teleosts in the China Sea are investigated using an integrative approach which combines morphological characteristcs, parasitic traits, and molecular data including small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer (ITS) regions. A novel species, Ceratomyxa dactyloptenasp. nov., was identified from the gallbladder of Oriental flying gurnard Dactyloptena orientalis Cuvier, 1829, while Ceratomyxa siganicola Zhang, Zhao, Yang & Yang, 2019 was found in the gallbladder of Mottled spinefoot Siganus fuscescens Houttuyn, 1782 and Mozambique tilapia Oreochromis mossambicus Peters, 1852. Mature myxospores of C. dactyloptenasp. nov. exhibit a crescent shape in sutural view, with dimensions of 30.0 ± 1.3 (27.2–32.8) µm in thickness, 6.4 ± 0.4 (5.7–7.0) µm in length, and a posterior angle of 152.9 ± 3.7° (146.2–158.9°). Pyriform polar capsules measured 2.9 ± 0.3 (2.3–3.3) µm long and 2.4 ± 0.3 (1.7–2.8) µm wide, with polar filaments coiled in 3–4 turns. The SSU rDNA sequence of C. dactyloptenasp. nov. was distinct from all known myxosporeans, showing the highest similarity (87.9%) and the shortest genetic distance (0.1209) with C. filamentosi Kalatzis, Kokkari & Katharios, 2013. Molecular analyses revealed intraspecific variation among C. siganicola strains, with ITS rDNA being more sensitive than SSU rDNA in detecting these differences. Phylogenetic analysis placed C. dactyloptenasp. nov. in a clade with C. oxycheilinae Heiniger, Gunter & Adlard, 2008, while all C. siganicola strains clustered together, forming a sister clade to C. barnesi Gunter, Whipps & Adlard, 2009. Furthermore, the phylogenetic results indicated that ceratomyxid diversification is influenced not only by host specificity but also by geographic distribution.