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

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.Versión del editor2,080

Extraordinary Dinoflagellates : Past and Present

This paper highlights the astonishing diversity of both form and function in a group of protists that were once obscure, but which now attract considerable attention from cell biologists, evolutionists, ecologists, aquaculturists and even public health authorities. They surprise and confuse all those who learn about them. For example, having only 50% of the species photosynthetic, they have been claimed to be plants (algae) by botanists and animals (protozoa) by zoologists and were separately classified as such, but both were wrong: they are flagellated protists belonging to the Alveolates and evolutionarily diverged in the Neoproterozoic, long before true animals and plants. However, they left little trace until the Mesozoic when, according to the record left by their highly resistant resting cysts, they radiated rapidly. The most likely explanation for this is the development of shallow continental shelves. Unlike many other groups they show little signs of extinction at the Cretaceous/Tertiary boundary, most major dinoflagellate lineages having persisted through more than 100 million years of Earth's history. As zooxanthellae they have contributed significantly to the success of reef-building corals. Present-day dinoflagellates are unusual in many ways. Their chromosomes are not constructed like all other eukaryotes, lacking histones. The nuclear envelope does not break down during mitosis and the spindle is extranuclear. They have multiple chloroplast types. The genome of the commonest type has fragmented into minicircles and only two genes have been identified in the mitochondrial genome. Their morphology is astonishingly diverse, ranging from unicellular to multicellular and even coenocytic. The heterotrophic forms have various, complex feeding mechanisms and even the photosynthetic ones may engulf prey (mixotrophy). They show remarkable examples of form mimicking multicellular organisms, such as resemblances to tapeworms, jellyfish, nematocysts and even eyes. They can be beneficial symbionts or deadly parasites. More than 70 species can produce deadly toxins which can kill marine life or, if concentrated by shellfish or fish, can kill humans.International Symposium on "Dawn of a New Natural History - Integration of Geoscience and Biodiversity Studies". 5-6 March 2004. Sapporo, Japan