2017 年 52 巻 3 号 p. 152-157
Morphological and molecular comparisons of Kudoa septempunctata isolates from 28 olive flounder Paralichthys olivaceus (19 from Japan, nine from Korea) were conducted to determine the geographical origin of infected flounders. Morphological examination showed that the frequency of spores with six polar capsules (PCs) was the highest (32%-86%) in all isolates examined, although there was a significant difference in the frequency of spores with seven PCs between Japanese (mean 2%, range 0%-15%) and Korean (mean 44%, range 12%-61%) isolates. The factor analysis showed that neither body weight of the host fish nor sampling time was significantly correlated to the frequency of spores with seven PCs. These results suggest that the frequency of spores with seven PCs can be used as an indicator to differentiate between Japanese and Korean isolates of K. septempunctata. In the molecular analysis, the isolates from the two countries had indistinguishable 18S-28S internal transcribed spacer (ITS) regions. However, comparative analysis of cytochrome b and NADH dehydrogenase subunit 1 region of mitochondrial DNA revealed that intraspecific variations existed within the Japanese and the Korean isolates, as well as in two isolates associated with food poisoning of unknown origin. Furthermore, the PCR-RFLP analysis on the region using the restriction enzymes Hpy188I and Hpy188III indicated that there were four types among the isolates. These morphological and molecular indicators may be useful to discriminate between the two geographical origins of K. septempunctata.
