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Ciguatera fish poisoning (CFP) is a serious health problem in tropical regions and is caused by the bioaccumulation of lipophilic toxins produced by dinoflagellates in the genus Gambierdiscus. Gambierdiscus species are morphologically similar and are difficult to distinguish from one another even when using scanning electron microscopy. Improved identification and detection methods that are sensitive and rapid are needed to identify toxic species and investigate potential distribution and abundance patterns in relation to incidences of CFP. This study presents the first species-specific, semi-quantitative polymerase chain reaction (qPCR) assays that can be used to address these questions. These assays are specific for five Gambierdiscus species and one undescribed ribotype. The assays utilized a SYBR green format and targeted unique sequences found within the SSU, ITS, and the D1/D3 LSU ribosomal domains. Standard curves were constructed using known concentrations of cultured cells and 10-fold serial dilutions of rDNA PCR amplicons containing the target sequence for each specific assay. Assay sensitivity and accuracy were tested using DNA extracts purified from known concentrations of multiple Gambierdiscus species. The qPCR assays were used to assess Gambierdiscus species diversity and abundance in samples collected from nearshore areas adjacent to Ft. Pierce and Jupiter, Florida USA. The results indicated that the practical limit of detection for each assay was 10 cells per sample. Most interestingly, the qPCR analysis revealed that as many as four species of Gambierdiscus were present in a single macrophyte sample. [ABSTRACT FROM AUTHOR]

A new photosynthetic dinoflagellate species, Coolia canariensis S. Fraga sp. nov., is described based on samples taken from tidal ponds on the rocky shore of the Canary Islands, northeast Atlantic Ocean. Its morphology was studied by LM and SEM. It is almost spherical and has a thick smooth theca with many scattered pores. Plate 1′ is the biggest of the epithecal plates, and 7″ is twice as wide as it is long. Phylogeny inferred from the D1/D2 regions of the LSU nuclear rDNA of three strains of C. canariensis and several strains of other Coolia species, C. monotis, C. sp., showed that C. canariensis strains clustered in a well-supported clade distinct from the other species. No toxins were detected using mouse bioassay, liquid chromatography with Fluorescence detection (LC-FLD) or liquid chromatography-mass spectrometry (LC-MS). Its pigment composition is of the peridinin type of dinoflagellates. Together with this new species, many other strains of C. monotis from the Atlantic Ocean and Mediterranean Sea have been analyzed for toxin presence, and no evidence of toxin production related to yessotoxins (YTXs) was found, as was previously suggested for C. monotis from Australia. [ABSTRACT FROM AUTHOR]

Intraspecific variation among 19 isolates of the ciguatera-causing dinoflagellate Gambierdiscus toxicus Adachi & Fukuyo (Dinophyceae) collected from French Polynesia, New Caledonia, and the French West Indies was investigated by isozyme analysis. Comparison of their cell sizes and growth rates revealed that significant variation exists among these enxyme systems indicated the G. toxicus is comprised of numerous biochemically distinct strains, Isolates from Tubuai and Hao appeared to be the most distantly related. Tahitian strains of G. toxicus also showed a remarkably low degree of similarity with the Tubuai isolates. The latter, which were taken from the same locale in Tubuai, also exhibited highly heterogeneous electrophoeretic profiles when compared to each other, suggesting a multiclonal origin. The single isolate analyzed from the Atlantic Ocean was most closely related to Tohitian isolates, depite their geographic separation. Finally, no clear relationship was found between the electrophoretic profiles of these isolates and their capacity to produce ciguatoxic compounds. [ABSTRACT FROM AUTHOR]

Examines clones of ciguatoxigenic Prorocentrum lima from different geographical areas. Surface morphology of the widely distributed clones; Number of valve pores; Periflagellar area of P. lima; Shape and size of P. lima.

Seventeen clones of the ciguatera-causing dinoflagellate Gambierdiscus toxicus Adachi and Fukuyo were to the same environments over several months. Signifacant variance environments over detected between non-acclimated and acclimated cultures for cell potencies, yields and reproduction rates. The resultant variance in acclimated potencies, yields and reproduction rates. The resultant variance in acclimated potencies among clones was statistically significant (P < 0.0001), indicating that potency can be used for a clone of G. toxicus in the acclimated vs. non-acclimated phases can exceed genetic differences between clones. This stresses the need for a rigorous acclimation process. Caribbean isolates of G. toxius were inherently more toxic than isolates from the other areas. One Caribbean clone yielded 55 × 10[sup-4] mu (mouse units)· cells[sup-1] where clones from Bermuda, the Bahamas, and Florida ranged from only 1.8 × 10[sup-4] Mu cell[sup-1] to a maximum of 19.8 × 10[sup-4] mu· cell[sup-1]. Toxicity decreased with increasing latitude (r = 0.819, P < 0.01), indicating that environmental differences probably influenced the potencies, A comparison of acclimated reproduction rates at four light intensities also indicated that genetic differences among clones existed. The resulting reproduction rate/light slopes overlapped, indicating that the clones may be adapted to specific light regimes. [ABSTRACT FROM AUTHOR]