Three novel Myxidium species (Myxozoa: Myxosporea) from fishes in river and small channels across Terengganu, Malaysia

Previously, only a single Myxidium species, Myxidium cf. notopterum from Notopterus notopterus , and two unidentified species from Tor tambroides and Barbonymus gonionotus had been reported in Malaysia. In the present study, three additional species, Myxidium acutum n. sp., Myxidium truncatum n. sp., and Myxidium orbiculare n. sp. were described from the gallbladders of freshwater fishes, Labiobarbus leptocheilus , Trichopodus pectoralis and Channa gachua , respectively, in Malaysia. Myxidium acutum n. sp. possessed elongated, fusiform spores with tapered ends and 6–7 valvular striations, measuring 12.5 ± 0.6 μm in length, 5.1 ± 0.4 μm in width, and 4.3 ± 0.4 μm in thickness. The polar capsules were equal and slightly pyriform, measuring 3.3 ± 0.3 μm × 2.7 ± 0.2 μm, each containing a tubule with 4–5 coils. Myxidium truncatum n. sp. exhibited elongated, fusiform spores with truncated ends and five valvular striations, measuring 11.7 ± 0.6 μm × 4.4 ± 0.3 μm × 3.8 ± 0.3 μm. Its pyriform polar capsules measured 3.8 ± 0.3 μm × 2.7 ± 0.2 μm with four coils. Myxidium orbiculare n. sp. had ellipsoidal, slightly concave spores with truncated ends and seven valvular striations, measuring 13.4 ± 0.4 μm × 6.5 ± 0.4 μm × 5.5 ± 0.3 μm, with rounded polar capsules bearing papilla-like tips (4.1 ± 0.3 μm × 3.3 ± 0.2 μm), each containing a tubule with four coils. Morphological, molecular, and phylogenetic analyses supported their recognition as new species and extended the known diversity and geographic distribution of Myxidium in Malaysia.