TAXONOMIC REVISION OF THE DINOFLAGELLATE AMPHIDOMA CAUDATA: TRANSFER TO THE GENUS AZADINIUM (DINOPHYCEAE) AND PROPOSAL OF TWO VARIETIES, BASED ON MORPHOLOGICAL AND MOLECULAR PHYLOGENETIC ANALYSES¹

Abstract

The systematic position of Amphidoma caudata Halldal within the genus Amphidoma has remained uncertain as a result of its plate formula and the absence of molecular phylogenetic data. Also, this thecate dinoflagellate taxon has been used to designate two distinct morphotypes. The present study aims to clarify the generic affiliation of Amphidoma caudata and the taxonomic value of two different morphotypes M1 and M2. The new examination of the plate formula using SEM showed that it was the same for both morphotypes and that it corresponded to the tabulation of the recent erected genus Azadinium Elbrächter et Tillmann. Morphometric analysis, using cell size, length of apical projection in conjunction with the cell length, and the ratio of horn and spine showed that M1 and M2 formed two distinct groups. These results were supported by a molecular approach, revealing notable differences in the sequences of LSU rDNA and ITS region between these two morphotypes. Phylogenetic analyses inferred either from LSU and combined SSU, ITS region and COI data positioned M1 and M2 in a sister cluster of Azadinium species while Amphidoma languida Tillmann, Salas et Elbrächter, the only species of Amphidoma for which sequence data were available, was situated in a basal position of the Azadinium clade. Thus, we propose the transfer of Amphidoma caudata to the genus Azadinium and, consequently, the rehabilitation of the original tabulation of the genus Amphidoma Stein. To discriminate the two morphotypes, we propose a rank of variety with the following designations: Azadinium caudatum var. caudatum and Azadinium caudatum var. margalefii.

Feeding by heterotrophic protists and copepods on the photosynthetic dinoflagellate Azadinium cf. poporum from western Korean waters

“…In this respect, it appears that A. cf. poporum acts similarly to A. caudatum (Nézan et al 2012). The reasons explaining these observations are unknown.…”

“…These species apparently seem to either remain at low density, such as A. caudatum, which was not observed to exceed 1.3 cells ml −1 (Nézan et al 2012), or are able to bloom (e.g. A. cf.…”

“…The production of AZAs was previously associated with a small photosynthetic dinoflagellate ), designated as Azadinium spinosum Elbrächter et Tillmann and assigned to a new genus ). The genus Azadinium is now composed of 4 well defined species, namely A. spinosum Elb räch ter et Tillmann ), A. obesum Tillmann et Elbrächter (Tillmann et al 2010), A. poporum Tillmann et Elbrächter (Tillmann et al 2011), and A. caudatum (Halldal) Nézan et Chomérat (Nézan et al 2012). Undefined species were also described as A. cf.…”

Morphology, molecular phylogeny and azaspiracid profile of Azadinium poporum (Dinophyceae) from the Gulf of Mexico

“…Up to ten species have been described in the past five years (Tillmann et al, , 2010Luo et al, 2013;Percopo et al, 2013). Additionally, Amphidoma caudata Halldal has been transferred to Azadinium based on both morphology and molecular phylogeny (Né zan et al, 2012). The genus Azadinium was characterized by a plate pattern of po, cp, x, 3-4 0 , 2-3a, 6 00 , 6C, 5S, 6 000 , 2 0000 Luo et al, 2013), in which the presence of anterior intercalary plates and a canal plate resembles the Peridiniales and the presence of six precingular and postcingular plates resembles the Gonyaulacales.…”

Gambierol: Synthetic Aspects

“…Generally, the location of the ventral pore seems to be quite variable in Azadinium species (Fig. 2 D-K 16 and A. polongum 20 . The pattern is consistent among the species, and identified an uncommon but stable imbrication pattern of the most dorsal apical plate (3′ in Azadinium or 4′ in Amphidoma), which characterized these two genera and might be helpful for a revision of the description of the family Amphidomataceae.…”