Gambierdiscus toxicus represents a multispecies complex: Implications for understanding ciguatera fish poisoning

Titre: 
Gambierdiscus toxicus represents a multispecies complex: Implications for understanding ciguatera fish poisoning
Auteurs: 
Litaker RW, Tester PA, Chinain M, Holmes MJ, Faust MA
Type de communication: 
Communication orale
Conférence: 
Congrès Ciguatéra et Biotoxines associées (Nouméa, Nouvelle-Calédonie)
Année: 
10/2008

Ciguatera fish poisoning (CFP) events are spatially and temporally variable. Whether this variability is due to changes in the distribution and abundance of different Gambierdiscus species having greater or lesser toxicity cannot be determined until the taxonomy of this genus is better resolved. This is important because, despite a poor correlation with overall cell abundances, CFP has been historically attributed primarily to “Gambierdiscus toxicus” or “Gambierdiscus sp”.
We will present detailed morphological and rDNA sequence data supporting at least 10 different Gambierdiscus species. Sequence data from single cell PCR also indicated other species exist as well. Identification of these potentially new species was possible because the phylogenetic analyses constructed using the original rDNA sequence data fell into discrete clusters which corresponded exactly with the described species. Many of the single cell sequences, however, fell into discrete genetic clusters different from the previously described species. Given that ten species were found despite a relatively limited sampling effort, it is likely that this genus, like Alexandrium, contains numerous species. Because many of the Gambierdiscus species are difficult to distinguish using light microscopy, we suggest that when the toxin profiles of individual isolates are being determined, that species-specific rDNA regions be sequenced at the same time. This approach provides an unambiguous means of establishing both intra and inter-specific differences in the types CFP toxins produced.
 Workshop international Ciguatéra et biotoxines associées (Nouméa, 27-31 octobre 2008)