Search

This study examined the toxicity of six Gambierdiscus species (Gambierdiscus belizeanus, Gambierdiscus caribaeus, Gambierdiscus carolinianus, Gambierdiscus carpenteri, Gambierdiscus ribotype 2 and Gambierdiscus ruetzleri) using a human erythrocyte lysis assay. In all, 56 isolates were tested. The results showed certain species were significantly more toxic than others. Depending on the species, hemolytic activity consistently increased by ∼7-40% from log phase growth to late log - early stationary growth phase and then declined in mid-stationary growth phase. Increasing growth temperatures from 20 to 31 °C for clones of G. caribaeus showed only a slight increase in hemolytic activity between 20 and 27 °C. Hemolytic activity in the G. carolinianus isolates from different regions grown over the same 20-31 °C range remained constant. These data suggest that growth temperature is not a significant factor in modulating the inter-isolate and interspecific differences in hemolytic activity. The hemolytic activity of various isolates measured repeatedly over a 2 year period remained constant, consistent with the hemolytic compounds being constitutively produced and under strong genetic control. Depending on species, greater than 60-90% of the total hemolytic activity was initially associated with the cell membranes but diffused into solution over a 24 h assay incubation period at 4 °C. These findings suggest that hemolytic compounds produced by Gambierdiscus isolates were held in membrane bound vesicles as reported for brevetoxins produced by Karenia brevis. Gambierdiscus isolates obtained from other parts of the world exhibited hemolytic activities comparable to those found in the Caribbean and Gulf of Mexico confirming the range of toxicities is similar among Gambierdiscus species worldwide. Experiments using specific inhibitors of the MTX pathway and purified MTX, Gambierdiscus whole cell extracts, and hydrophilic cell extracts containing MTX, were consistent with MTX as the primary hemolytic compound produced by Gambierdiscus species. While the results from inhibition studies require validation by LC-MS analysis, the available data strongly suggest differences in hemolytic activity observed in this study reflect maitotoxicity., (Published by Elsevier Ltd.)

Dinoflagellates in the genus Gambierdiscus produce toxins that bioaccumulate in tropical and sub-tropical fishes causing ciguatera fish poisoning (CFP). Little is known about the diversity and distribution of Gambierdiscus species, the degree to which individual species vary in toxicity, and the role each plays in causing CFP. This paper presents the first global distribution of Gambierdiscus species. Phylogenetic analyses of the existing isolates indicate that five species are endemic to the Atlantic (including the Caribbean/West Indies and Gulf of Mexico), five are endemic to the tropical Pacific, and that two species, Gambierdiscus carpenteri and Gambierdiscus caribaeus are globally distributed. The differences in Gambierdiscus species composition in the Atlantic and Pacific correlated with structural differences in the ciguatoxins reported from Atlantic and Pacific fish. This correlation supports the hypothesis that Gambierdiscus species in each region produce different toxin suites. A literature survey indicated a >100-fold variation in toxicity among species compared with a 2 to 9-fold within species variation due to changing growth conditions. These observations suggest that CFP events are driven more by inherent differences in species toxicity than by environmental modulation. How variations in species toxicity may affect the development of an early warning system for CFP is discussed., (Published by Elsevier Ltd.)

Ciguatera fish poisoning (CFP) is a circumtropical disease caused by ingestion of a variety of reef fish that bioaccumulate algal toxins. Distribution and abundance of the organisms that produce these toxins, chiefly dinoflagellates of the genus Gambierdiscus, are reported to correlate positively with water temperature. Consequently, there is growing concern that increasing temperatures associated with climate change could increase the incidence of CFP. This concern prompted experiments on the growth rates of six Gambierdiscus species at temperatures between 18 degrees C and 33 degrees C and the examination of sea surface temperatures in the Caribbean and West Indies for areas that could sustain rapid Gambierdiscus growth rates year-round. The thermal optimum for five of six Gambierdiscus species tested was >/=29 degrees C. Long-term SST data from the southern Gulf of Mexico indicate the number of days with sea surface temperatures >/=29 degrees C has nearly doubled (44 to 86) in the last three decades. To determine how the sea surface temperatures and Gambierdiscus growth data correlate with CFP incidences in the Caribbean, a literature review and a uniform, region-wide survey (1996-2006) of CFP cases were conducted. The highest CFP incidence rates were in the eastern Caribbean where water temperatures are warmest and least variable., (Published by Elsevier Ltd.)