LEPIDODINIUM VIRIDE GEN. ET SP. NOV. (GYMNODINAIALES, DINOPHYTA), A GREEN DINOFLAGELLATE WITH A CHLOROPHYLL A‐ AND B‐CONTAINING ENDOSYMBIONT^1,2

Abstract

A further description of the green dinoflagellate, strain Y‐100, with a chlorophyll a‐ and b‐containing endosymbiont is given with special emphasis on the morphology of the host cell. The host dinoflagellate cell is unarmored and has a gymnodinoid overall appearance. The theca or amphiesma basically consists of the outer membrane and flattened thecal vesicles in which no thecal plates are developed. Unusual hand basket‐shaped scales cover the entire cell surface together with a layer of mucilaginous material. These findings suggest that the organism is a new member of the Gymnodiniaceae (Gymnodiniales). We propose the name Lepidodinium viride gen. et sp. nov. The ultrasturcture of the host cell is typical of the dinoflagellates; however, the organism has 1) an unusual cytoplasmic projection that may be a homologue of the peduncle, 2) a single membrane‐bounded body containing membranous sheets, closely situated next to the endosymbiont, and 3) an electron opaque network‐forming appendage surrounding the transverse flagellum. Name of these features have been found in other dinoflagellates.

Phylogeny and Molecular Evolution of the Green Algae

“…While most photosynthetic dinoflagellates have secondary or tertiary plastids of red algal origin, members of the "green" dinoflagellate genus Lepidodinium have replaced their original red plastids with a new secondary endosymbiont from the green lineage (termed serial secondary endosymbiosis) (Watanabe et al, 1990;Keeling, 2010). Although prasinophytes had been hypothesized as the chloroplast source of Lepidodinium based on pigment composition (Watanabe et al, 1990), recent chloroplast multi-gene phylogenetic analyses suggest that these plastids were derived from an early representative of the core chlorophytes, but the exact donor lineage remains equivocal (Takishita et al, 2008;Matsumoto et al, 2011).…”

The Life History and Cell Cycle of Kryptoperidinium foliaceum, A Dinoflagellate with Two Eukaryotic Nuclei

“…Dinoflagellates are unique among eukaryotic algae in that they have taken the process of endosymbiosis one step further, since in several independent lineages the peridinin plastid has been replaced either with a successive secondary plastid or with a plastid from another secondary alga, resulting in tertiary plastids. Examples are the dinoflagellate groups of haptophyte (Karenia, Karlodinium, Takayama) (Yoon et al 2002), green algal (Lepidodinium) (Watanabe et al 1990), and diatom origin (Kryptoperidinium, Durinskia, Galeidinium, and Dinothrix as well as some species presently included in Peridinium [P. quinquecorne] and Gymnodinium [G. quadrilobatum]).The diatom endosymbiont is related to either centric (P. quinquecorne) (Horiguchi and Takano 2006) or pennate (Kryptoperidinium) (Chesnick et al 1996(Chesnick et al , 1997 groups. The tertiary endosymbiosis is more or less stable, depending on the dinoflagellate group, although knowledge of the symbiont-host system is limited, mainly restricted to genera such as Kryptoperidinium.…”

A single origin of the peridinin- and fucoxanthin-containing plastids in dinoflagellates through tertiary endosymbiosis

“…17 and 18), and prasinophyte-like plastid (i.e., Lepidodinium viride; ref. 19). Like Karlodinium and Karenia, all dinoflagellates containing anomalous plastids are thought to trace their ancestry to a peridinincontaining common ancestor (10,15).…”