Background
The marine epiphytic dinoflagellate genus
Gambierdiscus produce toxins that cause ciguatera fish poisoning (CFP): one of the most significant seafood-borne illnesses associated with fish consumption worldwide. So far, occurrences of CFP incidents in Japan have been mainly reported in subtropical areas. A previous phylogeographic study of Japanese
Gambierdiscus revealed the existence of two distinct phylotypes:
Gambierdiscus sp. type 1 from subtropical and
Gambierdiscus sp. type 2 from temperate areas. However, details of the genetic diversity and distribution for Japanese
Gambierdiscus are still unclear, because a comprehensive investigation has not been conducted yet.
Methods/Principal Finding
A total of 248 strains were examined from samples mainly collected from western and southern coastal areas of Japan during 2006–2011. The SSU rDNA, the LSU rDNA D8–D10 and the ITS region were selected as genetic markers and phylogenetic analyses were conducted. The genetic diversity of Japanese
Gambierdiscus was high since five species/phylotypes were detected: including two reported phylotypes (
Gambierdiscus sp. type 1 and
Gambierdiscus sp. type 2), two species of
Gambierdiscus (
G. australes and
G. cf.
yasumotoi) and a hitherto unreported phylotype
Gambierdiscus sp. type 3. The distributions of type 3 and
G. cf.
yasumotoi were restricted to the temperate and the subtropical area, respectively. On the other hand, type 1, type 2 and
G. australes occurred from the subtropical to the temperate area, with a tendency that type 1 and
G. australes were dominant in the subtropical area, whereas type 2 was dominant in the temperate area. By using mouse bioassay, type 1, type 3 and
G. australes exhibited mouse toxicities.
Conclusions/Significance
This study revealed a surprising diversity of Japanese
Gambierdiscus and the distribution of five species/phylotypes displayed clear geographical patterns in Japanese coastal areas. The SSU rDNA and the LSU rDNA D8–D10 as genetic markers are recommended for further use.
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