Kudoa septempunctata n. sp. (Myxosporea: Multivalvulida) from an aquacultured olive flounder (Paralichthys olivaceus) imported from Korea

Abstract

A new myxosporean species, Kudoa septempunctata n. sp. (Myxosporea: Multivalvulida), is described from the trunk muscles of an aquacultured olive flounder (Paralichthys olivaceus) imported from Korea. This species formed pseudocysts in the myofiber without inflammatory reactions, and the infection was not evident macroscopically. Spores of the new species were irregularly stellate in apical view, with the majority having seven unequal valves, each with a polar capsule of variable size (the remaining spores had six valves and polar capsules). The spores had dimensions of: width 11.8 (11.1-13.1); thickness 9.4 (8.9-10.0); length 8.5 (7.9-8.9); polar capsule length 4.6 (3.7-5.3); and polar capsule width 2.4 (2.2-2.8; mean with range in parentheses; n = 10; all measurements in micrometers). Scanning electron microscopy of the spores revealed unequal positioning of the seven valves without a definite center, rounded posterior ends of valves, and tiny projections at the apex of each valve. The small subunit ribosomal RNA gene (SSU rDNA) sequence of the new species was closely related to Kudoa spp. with five or more valves, particularly Kudoa thalassomi (97.6% identity) recorded from the trunk muscles of a moon wrasse (Thalassoma lunare) around the Australian continent. However, the latter species has six valves with a pointed edge and six polar capsules of a uniform size. The new species was also distinct from all presently known Kudoa spp. with seven valves and polar capsules, i.e. Kudoa yasunagai and Kudoa lethrini, regarding tissue tropism (trunk muscles versus brain), spore shape or external appendages, and SSU rDNA sequence.