Showing papers by "Takeshi Nakayama published in 2007"
TL;DR: Detailed electron microscopic observations revealed that D. brevis possesses all the key ultrastructural characters considered typical of Excavata, and it is classified as a new free‐living excavate in the Fornicata incertae sedis.
Abstract: Center for Computational Sciences and Institute of Biological Sciences, University of Tsukuba, 1-1-1 Tennodai,Tsukuba, Ibaraki 305-8577, JapanABSTRACT. Dysnectesbrevisn.gen.,n.sp.,afree-livingheterotrophicflagellatethatgrowsundermicroaerophilicconditionspossessestwo flagella. The posterior one lies in a ventral feeding groove, suggesting that this flagellate is an excavate. Our detailed electron mi-croscopic observations revealed that D. brevis possesses all the key ultrastructural characters considered typical of Excavata. Among the10 excavate groups previously recognized, D. brevis displays an evolutionary affinity to members of the Fornicata (i.e. Carpediemonas,retortamonads, and diplomonads). Firstly, a strong D. brevis Fornicata affinity was recovered in the phylogenetic analyses of smallsubunit ribosomal RNA (SSU rRNA) sequences, albeit the internal branching pattern of the D. brevis1Fornicata clade was not resolvedwithconfidence.CorrespondingtotheSSUrRNA phylogeny, D.brevisandtheFornicatashared thefollowing components oftheflagellarapparatus: the arched B fiber bridging the right root; a posterior basal body; and a left root. Combining both morphological and molecularphylogenetic analyses, D. brevis is classified as a new free-living excavate in the Fornicata incertae sedis.Key Words. Amitochondriate, Carpediemonas membranifera, diplomonads, Excavata, microaerophilic, retortamonads, typical excavates.
31 citations
TL;DR: The phylogenetic relationships of two unicellular green algae, Ignatius tetrasporus Bold et MacEntee and Pseudocharacium americanum Lee et Bold were investigated by ultrastructural and molecular methods and some features resemble those of the several organisms of the Siphonocladales sensu Floyd and O’Kelly.
Abstract: SUMMARY
The phylogenetic relationships of two unicellular green algae, Ignatius tetrasporus Bold et MacEntee and Pseudocharacium americanum Lee et Bold were investigated by ultrastructural and molecular methods. The zoospores from both species were covered neither by scales nor cell walls. The flagellar apparatus of the zoospores commonly included these features: the upper basal bodies were displaced counterclockwise in half to two-thirds of the basal body diameter and did not overlap with each other; the lower basal bodies were directly opposed or slightly displaced clockwise; the distal fiber had gently sigmoid central striations; terminal caps were absent from the ends of the basal bodies; a V-shaped proximal sheath extended from the upper basal bodies; a posterior fiber lay between the opposite lower basal bodies; and the coarsely striated band linked the sinister rootlet to the lower basal body. The suite of these features was not identical to that of any other quadriflagellate swimming cells, but some features including the lower basal body orientation, the striated distal fiber, and the coarsely striated fiber resemble those of the several organisms of the Siphonocladales sensu Floyd and O’Kelly. Phylogenetic analysis using 18S rDNA sequence data revealed that I. tetrasporus and P. americanum formed a monophyletic clade within the clade of Ulvophyceae sensu Lopez-Bautista and Chapman, but was not nested within any of the orders of the class that were examined.
27 citations
TL;DR: A new species of Nephroselmis is described from coastal waters of the Palau Islands and the southern part of Japan and a detailed comparison of morphological characters, such as chloroplast shape, position of eyespot, composition of hair scales, presence or absence of the two types of small square scales and the large spiny scales, reveals clear differences between the two species.
Abstract: A new species of Nephroselmis, Nephroselmis anterostigmatica, is described from coastal waters of the Palau Islands and the southern part of Japan. The long flagellum was stretched out at angle to the cell and showed a characteristic sigmoid line. A cup-shaped yellowish green chloroplast with two narrow sinuses included a pyrenoid with tubular invaginations of thylakoids. In contrast to other species of Nephroselmis, the eyespot was located at the anterior side of the cell. The transitional region of the flagellum possessed a single transitional plate and a stellate structure. The cell body was covered by two types of square scales (windmill/Maltese cross scales absent), small stellate scales and two types of large spiny scales. The flagellar surface was covered by inner square and outer rod-shaped scales, and ornamented with T- and Pl-hairs. Tip hairs are absent. Nephroselmis anterostigmatica is superficially similar to Nephroselmis pyriformis (N. Carter) Ettl, but a detailed comparison of morph...
27 citations