Morphology of Gambierdiscus excentricus (Dinophyceae) with emphasis on sulcal plates

Abstract

Gambierdiscus excentricus is an epibenthic dinoflagellate able to produce ciguatoxin and maitotoxin-like compounds that are responsible for ciguatera fish poisoning. Morphological descriptions and molecular characterization of two G. excentricus strains isolated from Brazil and maintained in culture were provided. The most complete description of the morphology of the sulcal region of Gambierdiscus based on light and scanning electron microscopy was presented. The sulcal area morphology and nomenclature used by different authors to name the sulcal plates in Gambierdiscus were reviewed. Two small sulcal plates (S.m.a. and S.m.p.) were shown for the first time. Phylogenetic trees based on D1–D3 and D8–D10 large subunits of ribosomal RNA gene sequences showed that the strains of G. excentricus from Brazil clustered with strains of G. excentricus isolated from its type locality, the Canary Islands. Both phylogenetic trees reconstructed the same relationships among all the formally described Gambierdiscus species and Gambierdiscus sp. ribotype 2 and Gambierdiscus sp. type 2.