Algal ciguatoxin identified as source of ciguatera poisoning in the Caribbean

Toxicity and underlying mechanism of the toxic dinoflagellate Gambierdiscus caribaeus to the fish Oryzias melastigma

Abstract Dinoflagellates in the genus Gambierdiscus are known to produce potent neurotoxins known as ciguatoxins. These toxins vector through the food web and can reach sufficiently high levels to cause ciguatera fish poisoning (CFP). In many regions of the Caribbean, little is known about the occurrence of CFP-causing species or the incidence of CFP, despite its apparent regional increase over the last few decades. Given the intraspecific variability in content and potencies of these toxins among Gambierdiscus species, the precise identification of local species of this genus is crucial. In this study we confirm the presence of the epibenthic dinoflagellate Gambierdiscus caribaeus in the Colombian continental Caribbean. Cells were collected in seagrass beds of Thalassia testudinum in Bonito Gordo, a site located on the western side of Bahía Concha, Tayrona National Natural Park, near the city of Santa Marta, Colombia. Subsequently, a single strain of Gambierdiscus could be established for further identification. Morphological (light and scanning electron microscopy), and molecular results (partial LSU and ITS rDNA sequencing) were consistent with the original description of G. caribaeus, as well as with the morphological characteristics shown by other authors in organisms obtained near the sampling area.

Distribution and potential toxicity of benthic harmful dinoflagellates in waters of Florida Bay and the Florida Keys

Population genetic studies provide insights into intraspecific diversity and dispersal patterns of microorganisms such as protists, which help understanding invasions, harmful algal bloom development and occurrence of seafood poisoning. Genetic differentiation across geography has been reported in many microbial species indicating significant dispersal barriers among different habitats. Temporal differentiation has been less studied and its frequency, drivers and magnitude are poorly understood due to a lack of integral studies. The toxic dinoflagellate species Gambierdiscus caribaeus was sampled during two years in the Florida Keys, and repeatedly from 2006 to 2016 at St. Thomas, US Virgin Islands (USVI), including a three-year period with monthly sampling, to compare spatial and temporal genetic differentiation. Samples from the USVI site showed high temporal variability in local population structure, which correlated with changes in salinity and benthic habitat cover. In some cases, temporal variability exceeded spatial differentiation, despite apparent lack of connectivity and dispersal across the Greater Caribbean Region based on the spatial genetic data. Thus, local processes such as selection might have a stronger influence on population structure in microorganisms than geographic distance. The observed high temporal genetic diversity challenges the prediction of harmful algal blooms and toxin concentrations, but illustrates also the evolutionary potential of microalgae to respond to environmental change.

Newly discovered role of the heterotrophic nanoflagellate Katablepharis japonica, a predator of toxic or harmful dinoflagellates and raphidophytes

Members of the benthic dinoflagellate genus Gambierdiscus are the causative agents of ciguatera fish poisoning worldwide. Ciguatera outbreaks appear to be more common in recent years and new incidences are reported from unprecedented regions. To investigate Gambierdicus population dynamics, connectivity, and dispersal routes, we developed microsatellite markers for Gambierdiscus caribaeus, a globally distributed species that is common at our study site at St. Thomas in the US Virgin Islands. We used high-throughput partial genome sequencing along with an existing transcriptome for microsatellite discovery. Screening of contigs with less than three times coverage resulted in 558 (partial genome) and 33 (transcriptome) candidate microsatellites. Four primer pairs from the partial genome and three from the transcriptome successfully amplified polymorphic microsatellites in multiplexed PCR reactions. The seven markers were tested on 150 G. caribaeus strains isolated monthly from August 2013 to July 2015 at St. Thomas, USVI. The numbers of alleles per locus varied between 3 and 14, and the allele diversity ranged from 0.214 to 0.899 in this dataset. These newly developed microsatellites will enable studies of population structure, connectivity, and dispersal in G. caribaeus and can give new insights into the expansion of ciguatera outbreaks worldwide.

Mixotrophy in the phototrophic dinoflagellate Takayama helix (family Kareniaceae): Predator of diverse toxic and harmful dinoflagellates

Effects of ocean warming on growth and distribution of dinoflagellates associated with ciguatera fish poisoning in the Caribbean

SummaryThe benthic dinoflagellates in the genus Gambierdiscus produce toxins that bioaccumulate in tropical and sub‐tropical fish causing ciguatera fish poisoning (CFP). Other co‐occurring genera such as Coolia have also been implicated in causing CFP. Little is known about the diversity of the two genera Gambierdiscus and Coolia along the Thai coasts. The results of morphological analyses based on observation under light microscopy and scanning electron microcopy showed that strains of Gambierdiscus from Thailand displayed the typical Gambierdiscus plate formula: Po, 4′, 0a, 6″, 6c,?s, 5′′′, 0p and 2′′′′. Morphological examination of Thai Gambierdiscus enabled it to be identified as Gambierdiscus caribaeus: round and anterior‐posteriorly compressed cell shape, broad 2′′′′ plate, rectangular 2′ plate, and symmetrical 3″ plate. The phylogenetic analyses based on the large subunit (LSU) rDNA D8/D10 sequences of Gambierdiscus from Thailand confirmed the morphological identification. The thecal plate formula for all of the Coolia isolates from Thailand was Po, 4′, 0a, 6″,?c,?s, 5′′′, 0p and 2′′′′. Most, but not all, of these isolates could be identified morphologically as Coolia malayensis. An LSU rDNA D1/D2 phylogenetic analysis confirmed identity of C. malayensis isolates identified morphologically. The remaining unidentified isolates fell in the C. tropicalis clade.

Gambierdiscus (Dinophyceae) species diversity in the Flower Garden Banks National Marine Sanctuary, Northern Gulf of Mexico, USA

Differences in the toxicity of six Gambierdiscus (Dinophyceae) species measured using an in vitro human erythrocyte lysis assay

Gambierdiscus spp. are epiphytic, benthic dinoflagellates. Some species have been shown to be toxic and cause ciguatera fish poisoning. We report, for the first time, the occurrence of Gambierdiscus caribaeus isolated from the waters off Jeju Island in Korea. Its morphology was similar to that of the original Belize strains of G. caribaeus. Gambierdiscus caribaeus has been reported in the tropical and subtropical waters of the Pacific, Gulf of Mexico, Caribbean Sea, and Floridian coast. Our report extends its range to the North Pacific Ocean. The plates of the Korean strain were arranged in a Kofoidian series of Po, 3', 7'', 6c, 6s, 5''', 1p, and 2'''', morphologically closer to other strains of G. caribaeus than to G. carpenteri. When properly aligned, its small subunit (SSU) rDNA was 0.5% different from those of Gambierdiscus sp. C-1, a strain that was isolated from the waters off eastern Japan, but was 2.4-4.0% different from those of the NOAA strains of G. caribaeus and 3.1-3.4% different from those of the NOAA strains of G. carpenteri. Additionally, the D1-D3 large subunit (LSU) rDNA sequence of the Korean strain of G. caribaeus was 4.7-5.3% different from those of the NOAA strains of G. caribaeus and 7.1-7.5% different from those of all reported G. carpenteri strains, including the NOAA strains. In phylogenetic trees based on SSU and LSU rDNA sequences, our Korean strain was basal to the clade consisting of the NOAA strains of G. caribaeus, which in turn was sister clade to all reported G. carpenteri strains.

Global distribution of ciguatera causing dinoflagellates in the genus Gambierdiscus

Litaker R.W., Vandersea M.W., Faust M.A., Kibler S.R., Chinain M., Holmes M.J., Holland W.C. and Tester P.A. 2009. Taxonomy of Gambierdiscus including four new species, Gambierdiscus caribaeus, Gambierdiscus carolinianus, Gambierdiscus carpenteri and Gambierdiscus ruetzleri (Gonyaulacales, Dinophyceae). Phycologia 48: 344–390. DOI: 10.2216/07-15.1Gambierdiscus species produce toxins that cause ciguatera fish poisoning (CFP), the most common nonbacterial illness associated with fish consumption worldwide. Understanding the role that individual Gambierdiscus species play in causing CFP is hampered because the morphologically similar species in the genus are difficult to distinguish. Ambiguities in the description of the type species Gambierdiscus toxicus also exist. This paper presents detailed line drawings along with additional scanning electron microscopy (SEM) and light micrographs to more fully characterize the six known Gambierdiscus species in addition to describing four new species, Gambierdiscus caribaeus sp. nov., Gambierdiscus carolinianus sp. nov., Gambierdiscus carpenteri sp. nov., and Gambierdiscus ruetzleri sp. nov. All four of the new species are photosynthetic and epibenthic and have a Kofoidian plate formula of Po, 3′, 7″, 6C, 6 or 7S, 5′″, 1p, and 2″″. Establishment of these species is supported by both morphological differences and three independent phylogenetic analyses utilizing small-subunit, as well as D1–D3 and D8–D10 large-subunit rDNA gene sequences. During the course of this study it became apparent that the description of the type species, G. toxicus, included more than one species. Since no type material exists we propose that Fig. 1 in Adachi and Fukuyo (1979) be designated as the lectotype for this species and that the epithecal view of isolate GTT-91 shown in Fig. 1 from Chinain et al. (1999) be designated as the epitype. The GTT-91 isolate has been well characterized genetically and the original SEM stub of this isolate archived at the Smithsonian Institution has been re-examined to provide a more detailed morphological analysis of the epitype.