|Title||Genetics and morphology characterize the dinoflagellate Symbiodinium voratum, n. sp., (dinophyceae) as the Sole representative of Symbiodinium clade e|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Jeong HJin, Lee SYeon, Kang NSeon, Yoo YDu, Lim ASuk, Lee MJoon, Kim HSeop, Yih W, Yamashita H, Lajeunesse TC|
|Journal||Journal of Eukaryotic Microbiology|
|Keywords||2014, phylogeny, plastid genes, rcc, rcc1521, rcc4008, species, systematics, taxonomy|
Dinoflagellates in the genus Symbiodinium are ubiquitous in shallow marine habitats where they commonly exist in symbiosis with cnidarians. Attempts to culture them often retrieve isolates that may not be symbiotic, but instead exist as free-living species. In particular, cultures of Symbiodinium clade E obtained from temperate environments were recently shown to feed phagotro-phically on bacteria and microalgae. Genetic, behavioral, and morphological evi-dence indicate that strains of clade E obtained from the northwestern, southwestern, and northeastern temperate Pacific Ocean as well as the Medi-terranean Sea constitute a single species: Symbiodinium voratum n. sp. Chlo-roplast ribosomal 23S and mitochondrial cytochrome b nucleotide sequences were the same for all isolates. The D1/D2 domains of nuclear ribosomal DNA were identical among Western Pacific strains, but single nucleotide substitu-tions differentiated isolates from California (USA) and Spain. Phylogenetic analyses demonstrated that S. voratum is well-separated evolutionarily from other Symbiodinium spp. The motile, or mastigote, cells from different cultures were morphologically similar when observed using light, scanning, and trans-mission electron microscopy; and the first complete Kofoidian plate formula for a Symbiodinium sp. was characterized. As the largest of known Symbiodi-nium spp., the average coccoid cell diameters measured among cultured iso-lates ranged between 12.2 (AE 0.2 SE) and 13.3 (AE 0.2 SE) lm. Unique among species in the genus, a high proportion (approximately 10–20%) of cells remain motile in culture during the dark cycle. Although S. voratum occurs on surfaces of various substrates and is potentially common in the plankton of coastal areas, it may be incapable of forming stable mutualistic symbioses.