Abstract
BackgroundThe 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 FindingA 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/SignificanceThis 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.
Highlights
Ciguatera fish poisoning (CFP) is one of the most significant marine food-borne illnesses caused by eating reef fish, it affects 25,000–500,000 people annually around the world; and this is endemic throughout the tropical and subtropical Pacific, Indian Ocean and the tropical Caribbean Sea [1,2,3,4,5,6,7]
RDNA and the large subunit (LSU) rDNA D8–D10 of Gambierdiscus spp. including species/phylotypes from Japan (Figs. 1 and 2) were almost the same and the same as that of the Maximum likelihood (ML) tree for the LSU rDNA D8–D10 of Gambierdiscus spp. including Japanese species/phylotypes (Fig. S1). The topologies of the former Bayesian inference (BI) trees were almost the same as that of BI tree of Gambierdiscus spp. for the small subunit (SSU) rDNA reported by Litaker et al [20] and those for the LSU rDNA D8–D10 reported by Fraga et al [15] and Litaker et al [20,21]
Genetic Diversity of Japanese Gambierdiscus A previous phylogeographic study of Japanese Gambierdiscus using the SSU rDNA and the ITS region revealed the existence of two putative allopatric phylotypes: Gambierdiscus sp. type 1 and Gambierdiscus sp. type 2 [22]
Summary
Ciguatera fish poisoning (CFP) is one of the most significant marine food-borne illnesses caused by eating reef fish, it affects 25,000–500,000 people annually around the world; and this is endemic throughout the tropical and subtropical Pacific, Indian Ocean and the tropical Caribbean Sea [1,2,3,4,5,6,7]. Common symptoms of this syndrome include gastrointestinal, neurological and cardiovascular disturbances [5,6,8]. Details of the genetic diversity and distribution for Japanese Gambierdiscus are still unclear, because a comprehensive investigation has not been conducted yet
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