MORPHOLOGY AND MOLECULAR ANALYSES OF THREE TOXIC SPECIES OF GAMBIERDISCUS (DINOPHYCEAE): G. PACIFICUS, SP. NOV., G. AUSTRALES, SP. NOV., AND G. POLYNESIENSIS, SP. NOV.

Abstract

Three new dinoflagellate species, Gambierdiscus polynesiensis, sp. nov., Gambierdiscus australes, sp. nov., and Gambierdiscus pacificus, sp. nov., are described from scanning electron micrographs. The morphology of the three new Gambierdiscus species is compared with the type species Gambierdiscus toxicus Adachi et Fukuyo 1979, and two other species: Gambierdiscus belizeanus Faust 1995 and Gambierdiscus yasumotoi Holmes 1998. The plate formula is: Po, 3′, 7", 6C, 8S, 5‴, 1p, 2"". Culture extracts of these three new species displayed both ciguatoxin‐ and maitotoxin‐like toxicities. The following morphological characteristics differentiated each species. 1) Cells of G. polynesiensis are 68–85 μm long and 64–75 μm wide, and the cell’s surface is smooth. They are identified by a large triangular apical pore plate (Po), a narrow fish‐hook opening surrounded by 38 round pores, and a large, broad posterior intercalary plate (1p) wedged between narrow postcingular plates 2‴ and 4‴. Plate 1p occupies 60% of the width of the hypotheca. 2) Cells of G. australes also have a smooth surface and are 76–93 μm long and 65–85 μm wide in dorsoventral depth. They are identified by the broad ellipsoid apical pore plate (Po) surrounded by 31 round pores and a long and narrow 1p plate wedged between postcingular plates 2‴ and 4‴. Plate 1p occupies 30% of the width of the hypotheca. 3) Cells of G. pacificus are 67–77 μm long and 60–76 μm wide in dorsoventral depth, and its surface is smooth. They are identified by the four‐sided apical pore plate (Po) surrounded by 30 round pores. A short narrow 1p plate is wedged between the wide postcingular plates 2‴ and 4‴. Plate 1p occupies 20% of the width of the hypotheca. These three newly described species were also characterized by isozyme electrophoresis and DNA sequencing of the D8–D10 region of their large subunit (LSU) rRNA genes. The consistency between species designations based on SEM microscopy and classification inferred from biochemical and genetic heterogeneities was examined among seven isolates of Gambierdiscus. Their classification into four morphospecies was not consistent with groupings inferred from isozyme patterns. Three molecular types could be distinguished based on the comparison of their LSU rDNA sequences. Although G. toxicus TUR was found to be more closely related to G. pacificus, sp. nov. than to other G. toxicus strains, the molecular classification was able to discriminate G. polynesiensis, sp. nov. and G. australes, sp. nov. from G. toxicus. These results suggest the usefulness of the D8–D10 portion of the Gambierdiscus LSU rDNA as a valuable taxonomic marker.

Morphology and rDNA phylogeny of a Mediterranean <em>Coolia monotis</em> (Dinophyceae) strain from Greece

“…appears to be minimal compared to that observed for Gonyaulacalean dinoflagellates (~10 to 50% IGV depending on the rDNA gene) such as Alexandrium (Scholin et al, 1994;Adachi et al, 1996;Guillou et al, 2002;John et al, 2003), Coolia (Penna et al, 2002), Ostreopsis (Pin et al, 2001;Penna et al, 2002), and Gambierdiscus (Babinchak et al, 1996;Chinain et al, 1999). This fact seems true even for the highly variable and quick evolving ITS region, but less evident for the slow evolving SSU.…”

“…(Pin et al, 2001;Penna et al, 2002) and Gambierdiscus spp. (Babinchak et al, 1996;Chinain et al, 1999). The intraspecific variability of potentially harmful benthic dinoflagellate taxa has raised interest in phenotypes as compared to genotypes from a taxonomic and biogeographic point of view.…”

Ciguatera-Causing Dinoflagellates in a Coral-reef Mangrove Ecosystem, Belize

“…This caused problems in earlier publications; for example, Gambierdiscus species have been identified either as Gambierdiscus toxicus and Gambierdiscus sp., or as Gambierdiscus multispecies complex with overlapping geographic distributions (i.e. Holmes, 1998;Chinain et al, 1999b). Four genera are illustrated in high resolution image (Fig.…”

“…No type material of G. toxicus is currently known . Later Chinain et al, (1999b) used living cultures of the original G. toxicus isolate and illustrated the species morphology in scanning electron micrographs; unfortunately no culture is available today. Holmes (1998) had frozen specimens G. toxicus GTT-91 which represent similar cell size, shape and morphology of thecal plates of G. toxicus Adachi et Fukuyo (1979) which is the epitype of the genus Gambierdiscus .…”

Madanidinium loirii gen. et sp. nov.(Dinophyceae), a new marine benthic dinoflagellate from Martinique Island, Eastern Caribbean

“…Subsequently, several other benthic taxa were found to be harmful and involved in the complex mechanism of ciguatera (Bomber & Aikman, 1989;Litaker et al, 2010). Because of this potential toxicity, several taxonomic studies were undertaken in tropical regions (Fukuyo, 1981;Besada et al, 1982;Berland et al, 1992;Grzebyk et al, 1994;Chinain et al, 1999) and also in temperate areas worldwide (e.g. Horiguchi & Chihara, 1983;Saunders & Dodge, 1984;Larsen, 1985;Hoppenrath, 2000b;Aligizaki & Nikolaidis, 2006;Murray, 2009;Chomérat et al, 2010b;Fraga et al, 2011).…”