Bispinodinium angelaceum gen. et sp. nov. (Dinophyceae), a new sand‐dwelling dinoflagellate from the seafloor off Mageshima Island, Japan¹

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.

Madanidinium loirii gen. et sp. nov.(Dinophyceae), a new marine benthic dinoflagellate from Martinique Island, Eastern Caribbean

“…With SSU, the position of this new genus is not stable in the trees, which indicates that this ribosomal gene lacks a good phylogenetic signal. This problem has already been pointed out with several other 'unusual' and monotypic genera of benthic dinoflagellates (Tamura & Horiguchi, 2005;Hoppenrath et al, 2007;Yamada et al, 2013). Moreover, no relationship was found to any of the morphologically related taxa with a lateral compression for which SSU rDNA sequences are available, such as Sabulodinium, Pileidinium and Thecadinium.…”

Pyramidodinium spinulosum sp. nov. (Dinophyceae), a sand‐dwelling non‐motile dinoflagellate from the seafloor (36 m deep) off Mageshima Island, Kagoshima, Japan

“…Recently, other dinoflagellates were described from similar depths in the same locality. Bispinodinium angelaceum (Yamada et al ) was obtained from the same sample from which P. spinulosum was isolated (July 2011) and Testudodinium magnum (Pinto et al ) was collected from the same locality at a depth of 35 m but on a different occasion (May 2012). Interestingly, both species are known to possess unique internal structures for dinoflagellates.…”

“…The sand samples were collected from the seafloor at a depth of 36 m, off Mageshima Island, Kagoshima Prefecture, Japan on 3 July 2011 using a Smith‐McIntyre bottom sampler (Rigosha, Tokyo). The light conditions and seawater temperature of this region have been described in Yamada et al (). A spoonful of the sand sample was placed in a disposable transparent plastic dish with a lid and enriched with Daigo's IMK medium (Nihon Pharmaceutical Co., Ltd., Tokyo) and cultured at 25°C with an illumination of 50 μmol photons m −2 s −1 with 16:8 h light : dark regime.…”

“…Recently Yamada et al () described a new genus and a species of sand‐dwelling dinoflagellate, Bispinodinium angelaceum N. Yamada & Horiguchi from a sandy seafloor at a depth of 36 m near Mageshima Island, Kagoshima Prefecture, Japan in the subtropical region of the Pacific Ocean. More recently, Pinto et al () described a new sand‐dwelling species, Testudodinium magnum Pinto, Terada & Horiguchi from a similarly deep (35 m) environment in the same area of the sea, but in the different date (30 May 2012).…”

“…More recently, Pinto et al () described a new sand‐dwelling species, Testudodinium magnum Pinto, Terada & Horiguchi from a similarly deep (35 m) environment in the same area of the sea, but in the different date (30 May 2012). The dinoflagellate described in this study was from the same sample, which we obtained B. angelaceum (Yamada et al ). This same sample also yielded an attached, coccoid dinoflagellate, covered with a dome‐shaped, spiny cell wall.…”