title: Tsukubamonas globosa n. gen., n. sp., a novel excavate flagellate possibly holding a key for the early evolution in "Discoba".
abstract: We report the ultrastructure and phylogenetic position of a free-living heterotrophic flagellate, Tsukubamonas globosa n. gen., n. sp. This flagellate was isolated from a pond in the University of Tsukuba, Japan. Under light microscopy, the spherical vegetative cells were naked and highly vacuolated, and always swam with rotating motion. Electron microscopic observations revealed that T. globosa possessed a ventral feeding groove, which is one of the hallmark characteristics of the supergroup Excavata. The position of T. globosa was unresolved in the small subunit ribosomal RNA phylogeny. On the other hand, a multigene phylogeny using α-tubulin, β-tubulin, actin, heat shock protein 90, and translation elongation factor 2 robustly united T. globosa with members of the "Discoba" clade of Excavata, composed of jakobids, euglenozoans, and heteroloboseans, although the precise position of T. globosa in this clade remained unresolved. Our detailed morphological comparisons elucidated that T. globosa possessed a novel set of morphological features, and could not be classified into any taxa in the Discoba clade. Instead we classified T. globosa into Tsukubamonadidae n. fam. under Tsukubamonadida n. ord.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Yabuki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakayama
authors.forename: Naoji
authors.initials: N
authors.lastname: Yubuki
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Ishida
authors.forename: Yuji
authors.initials: Y
authors.lastname: Inagaki
mesh_terms: D000199:Actins / Q000235:genetics; D059001:Aquatic Organisms / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D005075:Biological Evolution; D003599:Cytoskeleton / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D056898:Euglenozoa / Q000145:classification / Q000235:genetics; D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D005407:Flagella; D056145:Freshwater Biology; D006360:Heat-Shock Proteins / Q000235:genetics; D007564:Japan; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D061005:Ponds; D012335:RNA, Ribosomal / Q000235:genetics; D016415:Sequence Alignment; D014404:Tubulin / Q000235:genetics
chemical_list: D000199:Actins; D004275:DNA, Ribosomal; D006360:Heat-Shock Proteins; D012335:RNA, Ribosomal; D014404:Tubulin