CHARACTERIZATION OFOSTREOPSISANDCOOLIA(DINOPHYCEAE) ISOLATES IN THE WESTERN MEDITERRANEAN SEA BASED ON MORPHOLOGY, TOXICITY AND INTERNAL TRANSCRIBED SPACER 5.8S rDNA SEQUENCES1

Several isolates of epiphytic dinoflagellates belonging to the generaOstreopsisSchmidt andCooliaMeunier from the western Mediterranean Sea were examined by LM and EM, toxicity assays, and internal transcribed spacer (ITS) regions of nuclear rDNA, and 5.8S rDNA were sequenced. Morphological comparisons based on the analyses of cell shape, size, thecal plates, and surface ornamentation revealed two distinct species in the western Mediterranean:O. cf.siamensisSchmidt from the Catalan, Andalusian, and Sicilian coasts andO. ovataFukuyo from the Ligurian coast, southern Tyrrhenian Sea, and Balearic Islands. BothOstreopsisspecies were toxic; however, no differences in toxicity were detected between the twoOstreopsisspecies.Coolia monotisMeunier was nontoxic. The morphological studies were supported by phylogenetic analyses; all western Mediterranean isolates ofO. cf.siamensisshowed ITS and 5.8S rDNA sequences identical to each other and so did those ofO. ovata, whereas high genetic diversity was detected between the western Mediterranean and Asian isolates ofO. ovata. The nucleotide sequence analyses of theC. monotisstrains showed that allC. monotisisolates from Europe formed a homogeneous clade. Further, the genetic diversity was high between the European and AsianC. monotisisolates. In this study, genetic markers combined with morphology and toxicity analyses was useful in the taxonomic and phylogenetic studies of the Ostreopsidaceae in a temperate area.