title: Bispinodinium angelaceum gen. et sp. nov. (Dinophyceae), a new sand-dwelling dinoflagellate from the seafloor off Mageshima Island, Japan(1).
abstract: A new athecate dinoflagellate, Bispinodinium angelaceum N. Yamada et Horiguchi gen. et sp. nov., is described from a sand sample collected on the seafloor at a depth of 36 m off Mageshima Island, subtropical Japan. The dinoflagellate is dorsiventrally compressed and axi-symmetric along the sulcus. The morphology resembles that of the genus Amphidinium sensu lato by having a small epicone that is less than one third of the total cell length. However, it has a new type of apical groove, the path of which traces the outline of a magnifying glass. The circular component of this path forms a complete circle in the center of the epicone and the straight "handle" runs from the sulcus to the circular component. Inside the cell, a pair of elongated fibrous structure termed here the "spinoid apparatus" extends from just beneath the circular apical groove to a point near the nucleus. Each of two paired structures consists of at least 10 hyaline fibers and this is a novel structure found in dinoflagellates. Phylogenetic analyses based on the SSU and LSU RNA genes did not show any high bootstrap affinities with currently known athecate dinoflagellates. On the basis of its novel morphological features and molecular signal, we conclude that this dinoflagellate should be described as a new species belonging to a new genus.
authors.affiliation: Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
authors.forename: Norico
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Department of Fisheries, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan.
authors.forename: Ryuta
authors.initials: R
authors.lastname: Terada
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Tanaka
authors.affiliation: Department of Natural History Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Horiguchi
keywords: Amphidinium; Bispinodinium angelaceum gen. et. sp. nov.; PAR; apical groove; dinoflagellate; high-pressure freezing; photosynthetic pigments; sand-dwelling; spinoid apparatus; ultrastructure