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Gambierdiscus 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. [ABSTRACT FROM AUTHOR]

As part of a long-term study of benthic dinoflagellates from the Belizean barrier reef system, we report a new species: Prorocentrum levis M. A. Faust, Kibler, Vandersea, P. A. Tester et Litaker sp. nov. P. levis cells are oval in valve view and range in size from 40 to 44 μm long and 37 to 40 μm wide. Each valve surface is smooth, with 221–238 valve pores and 99–130 marginal pores. These pores are uniformly small and range in diameter from 0.13 to 0.19 μm. Asexual reproduction in P. levis is atypical, occurring within a hyaline envelope, and produces long branching chains of adherent cells. A phylogenetic analysis of SSU rDNA indicated that of the Prorocentrum species sequenced so far, P. levis was most closely related to P. concavum. P. levis produces okadaic acid and dinophysis toxin-2 (DTX2). Further, SEM observations and SSU rDNA sequence for P. belizeanum M. A. Faust, which was isolated at the same time, are also presented. [ABSTRACT FROM AUTHOR]

Pfiesteria shumwayaeGlasgow et Burkholder is assigned to a new genusPseudopfiesteriagen. nov. Plate tabulation differences betweenPfiesteriaandPseudopfiesteriagen. nov. as well as a maximum likelihood phylogenetic analysis based on rDNA sequence data warrant creation of this new genus. The Kofoidian thecal plate formula for the new genus is Po, cp, X, 4′, 1a, 6′′, 6c, PC, 5+s, 5′′′, 0p, 2′′′′. In addition to having six precingular plates,P. shumwayaecomb. nov. also has a distinctive diamond or rectangular-shaped anterior intercalary plate. BothPfiesteriaandPseudopfiesteriagen. nov. are reassigned to the order Peridiniales based on an apical pore complex (APC) with a canal (X) plate that contacts a symmetrical 1′, four to five sulcal plates, and the conservative hypothecal tabulation of 5′′′, 0p, and 2′′′′. These morphological characters and the life histories ofPfiesteriaandPseudopfiesteriaare consistent with placement of both genera in the Peridiniales. Based on the plate tabulations forP.shumwayae, P. piscicida, and the closely related“cryptoperidiniopsoid” and“lucy” groups, the family Pfiesteriaceae is amended to include species with the following tabulation: 4-5′, 0-2a, 5-6′′, 6c, PC, 5+s, 5′′′, 0p, and 2′′′′ as well as an APC containing a pore plate (Po), a closing plate (cp), and an X plate; the tabulation is expanded to increase the number of sulcal plates and to include a new plate, the peduncle cover (PC) plate. Members of the family have typical dinoflagellate life cycles characterized by a biflagellated free-living motile stage, a varying number of cyst stages, and the absence of multiple amoeboid stages. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]