Myxobolus binotati n. sp. (Myxozoa: Myxobolidae) from the ovaries of spotted barb, Barbodes binotatus (Valenciennes, 1842) in Terengganu, Malaysia.

To date, only 14 species have been reported worldwide from the ovaries of fish hosts. In the present study, a novel species, Myxobolus binotati n. sp., was described from the ovary of Barbodes binotatus. Spores were oval in frontal view and lemon-shaped in sutural view, measuring 10.7 × 8.3 × 6.2 μm. They possessed two unequal pyriform polar capsules, with larger measuring 4.8 ± 0.4 (4.0-5.8) μm in length, 2.8 ± 0.2 (2.4-3.4) μm in width, while smaller measuring 2.7 ± 0.3 (2.1-3.1) μm in length, 1.6 ± 0.2 (1.3-1.9) μm in width. Polar tubules coiled 7-8 and 4 turns in the larger and smaller capsules, respectively. The spores lacked an intercapsular appendix, iodinophilous vacuole, and mucous envelope, and possessed 8-10 asymmetrically distributed sutural markings. Molecular analysis of 18S rDNA gene revealed that the new species shared the highest sequence similarity (87.3%) with Myxobolus abitus found in the gills of Hypophthalmichthys molitrix. Phylogenetic analyses placed M. binotati n. sp. within a clade comprising species infecting the gills, fins, skin, scales, and ovaries, including several taxa characterized by unequal polar capsules. However, it formed a distinct lineage within this clade. The combined morphological, molecular, and phylogenetic evidence supports the establishment of M. binotati n. sp. as a new species.