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Parasitol Int. 2014 Aug;63(4):571-9. doi: 10.1016/j.parint.2014.03.006. Epub 2014 Apr 5.

Kudoa hexapunctata n. sp. (Myxozoa: Multivalvulida) from the somatic muscle of Pacific bluefin tuna Thunnus orientalis and re-description of K. neothunni in yellowfin tuna T. albacares.

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Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8657, Japan. Electronic address:
Tokyo Metropolitan Institute of Public Health, Hyakunin-cho, Shinjuku, Tokyo 169-0073, Japan.
Fisheries Laboratory, Kinki University, Shirahama Experimental Station, 3153 Shirahama, Nishimuro, Wakayama 649-2211, Japan.


Since Kudoa septempunctata in olive flounder (Paralichthys olivaceus) was indicated to cause food poisoning in humans, other Kudoa species are suspected to have pathogenic potential. Recently, a myxosporean possibly associated with food poisoning in humans consuming raw Pacific bluefin tuna, Thunnus orientalis, was identified as Kudoa neothunni. This is a known causative myxosporean of post-harvest myoliquefaction in yellowfin tuna Thunnus albacares. Regardless of the significant differences in the 28S rDNA sequence and the pathological character (with/without myoliquefaction) between the two T. orientalis and T. albacares isolates, they were considered intraspecific variants of K. neothunni. However, the light and low-vacuum electron microscopic observations in the present study revealed that there were two morphotypes; pointed- and round-type spores, which were significantly differentiated by the ratio of suture width to spore width. Furthermore, the two morphotypes were genetically distinguishable by the 28S rDNA sequence analysis. This morphological and molecular evidence validates that the two Kudoa types are separate species, and thus the pointed- and round-types are referred to as K. neothunni and Kudoa hexapunctata n. sp., respectively. K. neothunni was detected solely from T. albacares, whereas K. hexapunctata n. sp. was found not only from T. orientalis but also from T. albacares.


Food poisoning; Kudoa hexapunctata; Kudoa neothunni; Pacific bluefin tuna; Thunnus albacares; Thunnus orientalis

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