Kudoa azevedoi n. sp. (Myxozoa, Multivalvulida) from the oocytes of the Atlantic horse mackerel Trachurus trachurus (Perciformes, Carangidae) in Tunisian coasts.

A new species Kudoa azevedoi sp. n. (Myxozoa, Multivalvulida) is described in Trachurus trachurus Linnaeus, 1758 (Carangidae) from fishing harbors in Tunisian coasts using spore morphology and SSU rDNA sequence data. The parasite occurs only in ovaries within oocytes of mature and immature specimens. Spores are quadrate in shape in apical view with rounded edges, having four shell valves and four symmetrical polar capsules. They are of small sizes and measure 3.5±0.41 (3-4.2)×4.5±0.44 (4-5.2) length by width. The polar capsules are pyriform in shape measuring 1.5±0.22 (1.5-2)×0.75±0.14 (0.5-1) μm. Infected oocytes are hypertrophied, whitish colored, and filled with mature spores. Plasmodia are tubular and ramified from the inner membrane toward the center of the oocyte. Phylogenetic analysis based on small subunit ribosomal DNA sequences shows the highest similarity (96%) with the ovary parasite Kudoa ovivora. Some morphological details and spore dimensions support the creation of a new species in the genus Kudoa. Mean prevalence among examined females is of about 55.5%. It varies between localities and length of fish. The present myxosporea is the second Kudoa species reported in fish ovaries.