Studies on woloszynskioid dinoflagellates IV: The genus Biecheleria gen. nov.

The well known freshwater dinoflagellate Woloszynskia pseudopalustris is transferred to the new genus Biecheleria , based on the very unusual structure of the eyespot (comprising a stack of cisternae), the apical apparatus of a single elongate amphiesma vesicle, the structure of the resting cyst, and molecular data. Biecheleria is phylogenetically related to Symbiodinium and Polarella of the family Suessiaceae. This family, which extends back to the Jurassic, is redefined with the eyespot (Type E sensu Moestrup and Daugbjerg) and apical apparatus as diagnostic features, unknown elsewhere in the dinoflagellates. Biecheleria also comprises the brackish water species Biecheleria baltica sp. nov. (presently identified as Woloszynskia halophila ) and the marine species Biecheleria natalensis (syn. Gymnodinium natalense ). Gymnodinium halophilum described in 1952 by B. Biecheler but apparently not subsequently refound, is transferred to Biecheleria . The Suessiaceae further includes the marine species Protodinium simplex , described by Lohmann in 1908 but shortly afterwards (1921) transferred to Gymnodinium by Kofoid and Swezy and subsequently known as Gymnodinium simplex . It only distantly related to Gymnodinium . A new family, the Borghiellaceae, is proposed for the sister group to the Suessiaceae, based on eyespot structure (Type B of Moestrup and Daugbjerg), the morphology of the apical apparatus (if present), and molecular data. It presently comprises the genera Baldinia and Borghiella . Cells of Biecheleria pseudopalustris and B. baltica contain a microtubular strand (msp) associated with vesicles containing opaque material. Such structures are known in other dinoflagellates to serve as a peduncle, indicating that the two species may be mixotrophic.     

Light and electron microscopical studies onHafniomonas gen. nov. (Chlorophyceae,Volvocales), a genus resemblingPyramimonas (Prasinophyceae)

Based on light and electron microscopical studies ofPyramimonas reticulata the genusPyramimonas is shown to contain a number of unrelated flagellates.P. reticulata andP. montana are transferred to the new genusHafniomonas, cells of which differ fromPyramimonas in shape, in the absence of scales and hairs on the body and flagellar surfaces, in details of the chloroplast, the position of the nucleus, the Golgi apparatus, the internal structure of the flagellar apparatus, and in cell division. The prasinophytePyramimonas contains a characteristic association of a large microbody and a rhizoplast, situated on the nuclear surface. A similar association is being found in an increasing number of prasinophycean flagellates, but is absent inHafniomonas, which is considered related to chlorophycean rather than prasinophycean flagellates. The phylogenetic position ofHafniomonas is discussed, based in particular on details of the unique flagellar apparatus.     

DEVELOPMENT OF THE FLAGELLAR APPARATUS OF NAEGLERIA

Flagellates of Naegleria gruberi have an interconnected flagellar apparatus consisting of nucleus, rhizoplast and accessory filaments, basal bodies, and flagella. The structures of these components have been found to be similar to those in other flagellates. The development of methods for obtaining the relatively synchronous transformation of populations of Naegleria amebae into flagellates has permitted a study of the development of the flagellar apparatus. No indications of rhizoplast, basal body, or flagellum structures could be detected in amebae. A basal body appears and assumes a position at the cell surface with its filaments perpendicular to the cell membrane. Axoneme filaments extend from the basal body filaments into a progressive evagination of the cell membrane which becomes the flagellum sheath. Continued elongation of the axoneme filaments leads to differentiation of a fully formed flagellum with a typical "9 + 2" organization, within 10 min after the appearance of basal bodies.     

THE FLAGELLAR APPARATUS OF GYMNODINIUM SP. (DINOPHYCEAE)1

The detailed structure of the flagellar apparatus has been determined in a small dinoflagellate of the genus Gymnodinium. Although diminutive, this dinoflagellate possesses a complex flagellar apparatus consisting of a posteriorly directed microtubular root, a transverse striated fibrous root, several striated fibrous connectives that attach the basal bodies to one another as well as to the different roots, and a conspicuous non-striated fibrous connective that directly links the posteriorly directded microtubular root with the extended lobe of the nucleus. This represents the second discovery of a nuclear connective linked to the flagellar apparatus in the Dinophyceae but is the first report to elucidate the spatial relationships of the connective with the flagellar apparatus and the cell. A detailed diagrammatic reconstruction is provided and the similarities between these flagellar apparatus features are compared with those known for other dinoflagellates. Additionally, the structure and displacement of the nuclear connective are compared with nuclear connectives described in other protists.     

The flagellar root apparatus,the microtubular system and associated organelles in the chrysophycean flagellate,Poterioochromonas malhamensis Peterfi (syn.Poteriochromonas stipitata Scherffel andOchromonas malhamensis pringsheim)

Summary The two flagella ofPoterioochromonas are inserted in an apical platform which is shaped by six long flagellar root fibres. The arrangement and structure of these root fibres are described in detail. One of these fibres is the single nucleating site for cytoplasmic interphase microtubules which extend peripherally down to the cytoplasmic tail. Another fibre proceeds toward the centre of the cell and passes the nucleus but is different in structure, position and function from the striated rhizoplast found in many chrysophycean flagellates which is observed but vestigial inPoterioochromonas.A specific kinetosomal mitochondrion has a threefold attachment to the flagellar root apparatus. The chloroplast is also bound to the root system. It has no stigma, but a special continuation of the periplastidial cisterna is developed instead. Another cisterna extends from the nuclear envelope-dictyosome interspace to the kinetosome of the long flagellum. The functional and taxonomic meanings of these structures and of their mutual arrangement are discussed. It is concluded that the present strain (no. 933-1 a of the Collection of Algal Cultures at the Institute of Plant Physiology, Göttingen) has to be excluded from the genusOchromonas.     

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

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.     

广东四片藻鞭毛器的亚微结构和囊壳的形成

本文详细研究了1种海生4条鞭毛的单胞绿藻——广东四片藻鞭毛器的亚微结构和囊壳的形成。4条鞭毛着生于细胞前端凹陷的基部,鞭毛表面覆盖2层鳞片;基体呈纵向平行的“Z”字形排列;具纹纤维连接内外径向排列的两个基体;4个片层状的卵形盘(或称半桥粒(halfdesmosome))微管和纤维物质构成的复合体将鞭毛器和根丝体固着在质膜和囊壳上。根丝体通过两束交叉的微管带与两个邻近的外侧基体相连接。这种连接方式与其它已研究过的四片藻是不同的。囊壳的形成开始于内膜系统,特别是高尔基体。纤维丛和电子密集颗粒在其中合成、修饰,同时由高尔基体衍生的小泡转移到原生质体表面特定的区域,然后经若干步骤接合成完整的囊壳。这个区域与蛋白核的位置相关,表明聚合星状颗粒酶是在蛋白核位点制造或释放的,同时分泌到细胞外。囊壳沿边生长组装与细胞质发育产生特征性的前端鞭毛凹陷同时发生。     

Ultrastructure of the dinoflagellate Polykrikos. II. The nucleus and its connections to the flagellar apparatus

Electron microscopy of the colonial dinoflagellate Polykrikos kofoidi revealed a nuclear cortex formed of two electron-dense cortical layers directly beneath the nuclear envelope. Nuclear pores were confined to vesicular outpocketings of the nuclear envelope over circular discontinuities in the cortical layers. A conspicuous fibrous ribbon extended from the nucleus to the flagellar apparatus of each zooid. The ribbons resembled in their structure and position the attractophores of termite flagellates. Each flagellar apparatus consisted of two flagella, two elongate axial kinetosomes, an oblique kinetosome, and two roots of markedly different periodicities.     

COMPARATIVE ANALYSES OF THE DINOFLAGELLATE FLAGELLAR APPARATUS. II. CERATIUM HIRUNDINELLA1

The three-dimensional structure of the flagellar apparatus in the gonyaulacoid dinoflagellate. Ceratium hirundinella var. furcoïdes (Schröder) Hub.-Pest. was determined using serial section electron microscopy. The flagellar apparatus is quite large and consists of several components. The two basal bodies nearly abut at their proximal ends and are separated by an angle of approximately 120° The broad longitudinal microtubular root extends from the cell's left edge of the longitudinal basal body and bends around the sulcal/cingular depression into the cell's left antapical horn. A transverse striated fibrous root is associated with the transverse basal body and a narrow electron dense extension is present along the anterior edge of the transverse basal body. This study revealed severa1 hitherto unreported fibrous components of the flagellar apparatus that link the various microtubular and fibrous components to themselves and to the two striated collars. A large striated fibrous connective links the two striated collars to one another. This fibrous connective is linked to another striated fibrous connective that originates from the longitudinal basal body and lies perpendicular to the longitudinal microtubular root. The readily identifiable and numerous components of the Ceratium flagellar apparatus are comparable to those of other dinoflagellates. The combined presence of well dpveloped striated collars, a striated collar connective, and a basal body angle of approximately 120° indicates that this flagellar apparatus is most like that described for Peridinioid dinoflagellates. Important similarities are also noticeable between this flagellar apparatus and that of Oxyrrhis marina.     

Ultrastructure of the flagellar apparatus of the green algaTetraselmis subcordiformis

Summary The ultrastructure of the flagellar apparatus of the marine quadriflagellate green algaTetraselmis subcordiformis is described in detail. Special consideration is given to the functional significance of the contractile rhizoplast and also to a complex structure which anchors the flagellar apparatus to the cell membrane and theca. The flagellar apparatus lies at the base of a deep apical depression. Four basal bodies lie in a zigzag row with their long axes nearly parallel. Outer adjacent pairs of basal bodies are structurally linked by a Z-shaped, ribbon-like structure. A striated fiber (transfiber) connects each outer basal body with the inner basal body of the opposite, mirror image pair. A complex system of four laminated oval discs (rhizanchora), microtubule rootlets and fibrous material anchor the flagellar apparatus and rhizoplasts to the plasma membrane and theca. A 4-2-4-2 arrangement of microtubule rootlets is present. Rhizoplasts, which are contractile organelles, branch into five distinct arms and associate with the near outer basal body and each of the four rhizanchora. Rhizoplast contraction is thought to be linked to flagellar activity and may act to alter the direction of motion of the cell.     

COMPARATIVE ANALYSES OF THE DINOFLAGELLATE FLAGELLAR APPARATUS. I. WOLOSZYNSKIA SP.1

The three-dimensional structure of the flagellar apparatus in Woloszynskia sp. was determined. This recently discovered dinoflagellate possesses two basal bodies that are offset from one another and lie at an angle of approximately 110°. The transverse basal body is associated with a striated fibrous root assemblage that consists of two differently staining fibrous portions with identical striation periodicity. Unlike the transverse striated fibrous roots reported in other dinoflagellates, this assemblage extends to the cell's right beyond the proximal end of the transverse basal body. The striated fibrous root complex is attached to the anterior end of the longitudinal microtubular root by a broad striated fibrous connective. The longitudinal basal body is also associated with the longitudinal microtubular root. The flagellar opening of each emerging axoneme is surrounded by a striated collar. The striated collars are linked to one another by a striated fibrous, striated collar connective. The variations and similarities of the flagellar apparatus and the ventral ridge/striated collar connective in Woloszynskia sp. are compared to similar components in other dinoflagellates.     

The 3D Structure of the Apical Complex and Association with the Flagellar Apparatus Revealed by Serial TEM Tomography in Psammosa pacifica,a Distant Relative of the Apicomplexa

The apical complex is one of the defining features of apicomplexan parasites, including the malaria parasite Plasmodium, where it mediates host penetration and invasion. The apical complex is also known in a few related lineages, including several non-parasitic heterotrophs, where it mediates feeding behaviour. The origin of the apical complex is unclear, and one reason for this is that in apicomplexans it exists in only part of the life cycle, and never simultaneously with other major cytoskeletal structures like flagella and basal bodies. Here, we used conventional TEM and serial TEM tomography to reconstruct the three dimensional structure of the apical complex in Psammosa pacifica, a predatory relative of apicomplexans and dinoflagellates that retains the archetype apical complex and the flagellar apparatus simultaneously. The P. pacifica apical complex is associated with the gullet and consists of the pseudoconoid, micronemes, and electron dense vesicles. The pseudoconoid is a convex sheet consisting of eight short microtubules, plus a band made up of microtubules that originate from the flagellar apparatus. The flagellar apparatus consists of three microtubular roots. One of the microtubular roots attached to the posterior basal body is connected to bypassing microtubular strands, which are themselves connected to the extension of the pseudoconoid. These complex connections where the apical complex is an extension of the flagellar apparatus, reflect the ancestral state of both, dating back to the common ancestor of apicaomplexans and dinoflagellates.     

Fine structure of photo-kinetic systems in Dinobryon cylindricum var. Alpinum (chrysophyceae)

The ultrastructure of the stigma and associated flagellar-microtubular systems in Dinobryon cylindricum var. alpinum is described in detail and compared with observations on comparable photo-kinetic systems in other chrysophycean organisms. The chloroplastidic stigma of D. cylindricum var. alpinum is shown to lie in a particular positional relationship to the flagellar swelling in the anterior furrow and to several other organelles, to consist of a monolayer of c. 40 pigmented granules, each c. 250–500 nm diameter, arranged in a definite pattern, and to be overlain by several membrane systems. Other cytoplasmic pigmented bodies with dense crystalline contents surrounded by a single “unit membrane” aggregate near the anterior furrow on the side opposite the stigma. The swelling on the proximal portion of the smooth flagellum is separated from the plasmalemma of the anterior furrow by a nearly constant distance of 75–100 nm, has a multilamellate substructure that is linked by fine radiating interconnections to the axoneme doublets, and is connected to the plasmalemma by a system of fibrillar interconnections. A transitional helix in the basal body region is described as similar to structures reported in other chrysophycean flagellates. A striated rhizoplast with a periodicity of c. 90 nm extends from basal body I to the nuclear envelope. A seven-stranded microtubular root extends from the same basal body. Other fibrous and microtubular root systems are also described. The inter-relationships and possible functions of the aforementioned structures are discussed.     

Relationship between the flagellates and the ciliates.

The flagellates and the ciliates have long been considered to be closely related because of their unicellular nature and the similarity in the structures of the axoneme of the flagella and cilia in both groups. Most protozoologists believe that the ciliates arose from a flagellate. The flagellates that are most similar in structure to the ciliates are the dinoflagellates and two genera of uncertain taxonomic position, Colponema and Katablepharis. Structurally, dinoflagellates have a number of similarities with ciliates. These include the similarity of the cortical alveoli in the ciliates to the thecal vesicles in the dinoflagellates, the possession of tubular cristae, the similarity of the parasomal sac of the ciliates to the pusule of the dinoflagellates, the possession of similar trichocysts and mucocysts, and some similarity in the feeding apparatus. Colponema spp. are probably related to the dinoflagellates and have many of the same similarities with the ciliates. Katablepharis spp. are very similar in structure to the swarmer (embryo) of the suctorian ciliates. Indeed, reduction in the number of cilia to two in the suctorian swarmer and elimination of the macronucleus would result in a cell that is very similar to the Katablepharis cell. The feeding apparatus of Katablepharis spp. and the rest of the ciliates consists of two concentric microtubular arrays associated with vesicles. Information available from nucleotide sequencing of rRNA places the dinoflagellates in an ancestral position to the ciliates. The rRNA of Colponema and Katablepharis spp. has not yet been investigated. The use of stop codons in mRNA is discussed in relation to phylogeny.     

Ultrastructure and large subunit rDNA sequences of Lepidodinium viride reveal a close relationship to Lepidodinium chlorophorum comb. nov. (=Gymnodinium chlorophorum)

The ultrastructure of the green dinoflagellate Lepididodinium viride M. M. Watanabe, S. Suda, I. Inouye Sawaguchi et Chihara was studied in detail. The nuclear envelope possessed numerous chambers each furnished with a nuclear pore, a similar arrangement to that found in other gymnodinioids. The flagellar apparatus was essentially identical to Gymnodinium chlorophorum Elbrächter et Schnepf, a species also containing chloroplasts of chlorophyte origin. Of particular interest was the connection of the flagellar apparatus to the nuclear envelope by means of both a fiber and a microtubular extension of the R3 flagellar root. This feature has not been found in other dinoflagellates and suggests a close relationship between these two species. This was confirmed by phylogenetic analysis based on partial sequences of the large subunit (LSU) rDNA gene of L. viride, G. chlorophorum and 16 other unarmoured dinoflagellates, including both the ‘type’ culture and a new Tasmanian isolate of G. chlorophorum. These two isolates had identical sequences and differed from L. viride by only 3.75% of their partial LSU sequences, considerably less than the difference between other Gymnodinium species. Therefore, based on ultrastructure, pigments and partial LSU rDNA sequences, the genus Lepidodinium was emended to encompass L. chlorophorum comb. nov.     

COMPARATIVE ANALYSIS OF THE DINOFLAGELLATE FLAGELLAR APPARATUS IV. GYMNODINIUM ACIDOTUM1

Gymnodinium acidotum Nygaard is a freshwater dinoflagellate that is known to harbor a cryptomonad endosymbiont whose chloroplasls give the organism an overall blue-green color. The ultrastructure of G. acidotum was examined with particular attention being given to the three dimensional nature of the flagellar apparatus. The fiagellar apparatus is composed of two functional basal bodies that are slightly offset and lie at an angle of approximately 90° to one another. As in other dinoflagellates the transverse basal body is associated with a striated, fibrous root that extends from the proximal end of the basal body to the transverse flagellar opening. At least one microtubular root extends from the proximal end of the transverse basal body, and a multi-membered longitudinal microtubular root is associated with the longitudinal basal body. The most striking feature of the flagellar apparatus of G. acidotum is the large fibrous connective that extends from the region of the proximal ends of the basal bodies to the cingulum on the dorsal side of the cell. A similar structure has been reported from only one other dinoflagellate, Amphidinium cryophilum Wedemayer, Wilcox, and Graham. The presence of this structure as well as similarities in external morphology suggest thai these two species may be more closely related to each other than either is to other gymnodinioid taxa. The taxonomic importance of dinoflagellate flagellar apparatus components is discussed.     

The cytology and ultrastructure of zoospores of Hydrurus foetidus (Chrysophyceae)

The unusual tetrahedral shape of Hydrurus foetidus (Vill.) Trev. zoospores is associated with a complex skeletal system of microtubules extending from a broad flagellar root (up to 19 microtubules) into each of three, pointed anterior processes. The posterior end, also pointed and supported by a separate set of microtubules, contains a single large chloroplast with a prominent posterior furrow containing mitochondrial elements. A large immersed pyrenoid is penetrated by paired thylakoids. There is no eyespot. Numerous large Golgi bodies occur immediately anterior to the nucleus and up to 5–6 contractile vacuoles lie near the cell surface at the anterior end. Two terminally inserted flagella extend from the cell surface, a long one serving for cell locomotion, and the other vestigial with an axonemal pattern of 9+0. The flagellar root system consists of: (1) a thin, striated rhizoplast extending from the basal body of the long flagellum and ramifying over the surface of a conspicuous, anteriorly directed, conical projection of the nucleus; (2) a broad microtubular root which emanates from near the basal body of the long flagellum and appears to function as a MTOC; (3) a compound root, consisting of a striated fiber and two associated microtubules, which runs alongside the basal body of the stubby flagellum before terminating at the cell surface; and (4) a short two-membered microtubular root, also associated with the basal body of the stubby flagellum. Other components of the flagellar apparatus include a large dense body near the proximal end of the basal body of the short flagellum, and a small, dense, core-like structure closely associated with one of its triplet fibers. The flagellar apparatus of H. foetidus is remarkably similar in ultrastructure to that of Chrysonebula holmesii Lund.     

Taxonomy and phylogeny of a new kleptoplastidal dinoflagellate, Gymnodinium myriopyrenoides sp. nov. (Gymnodiniales, Dinophyceae), and its cryptophyte symbiont

A new kleptoplastidal dinoflagellate, Gymnodinium myriopyrenoides sp. nov., was described using light microscopy, electron microscopy and phylogengetic analysis based on partial LSU rDNA sequences. Cells were dorsiventrally flattened, elongate-elliptical in ventral view. There was no displacement of the cingulum encircling the anterior part of the cell. The cingulum was curved posteriorly at the terminal junction with the sulcus. The sulcus was generally narrow but expanded in the posterior end. The epicone possessed an apical groove made of one and one-half counterclockwise revolutions. Phylogenetic analysis based on LSU rDNA showed that the sequence of G. myriopyrenoides was included in the Gymnodiniales sensu stricto clade and had special affinities with the species Amphidinium poecilochroum and Gymnodinium acidotum, which also harbor kleptochloroplasts. Phylogenetic analysis based on plastid-encoded SSU rDNA and ultrastructural observations suggested that the symbionts of G. myriopyrenoides were cryptophytes of the genus Chroomonas or Hemiselmis. Organelles including the nucleus, the nucleomorph, mitochondria, Golgi bodies and large chloroplasts remained in the cytoplasm of the symbionts, but not the periplast, ejectosomes or flagellar apparatus. The symbiotic level of G. myriopyrenoides was estimated to be a relatively early stage in the unarmored kleptoplastidal dinoflagellates.     

Ultrastructural and immunocytological studies on the rhizoplast in the chrysophycean alga Ochromonas danica

The rhizoplast, a striated band elongating from the flagellar basal body to the nucleus, is conspicuous in cells of Ochromonas danica Prings. In interphase cells, it runs from the basal body of the anterior flagellum to the space between the nucleus and the Golgi body. In O. danica, the rhizoplast duplicates during mitosis and the two rhizoplasts serve as mitotic poles. In the present study, we reinvestigated mitosis of O. danica using transmission electron microscopy and immunofluorescence microscopy, especially focusing on the rhizoplast. The nuclear envelope became dispersed during metaphase, and the rhizoplasts from two sets of the flagellar basal bodies functioned as the mitotic poles. Immunofluorescence microscopy using anti‐α‐tubulin, anti‐centrin and anti‐γ‐tubulin antibodies showed that centrin molecules were localized at the flagellar basal bodies, whereas γ‐tubulin molecules were detected at the rhizoplast during the whole cell cycle.     

THE FLAGELLAR APPARATUS OF THE ZOOSPORE OF UROSPORA PENICILLIFORMIS(CHLOROPHYTA)1

The flagellar apparatus of Urospora penicilliformis (Roth) Aresch. is unique, or at least very unusual among green algae. The flagellar axonemes are rigid, and contain wing-like projections. There are no central microtubules in the most proximal part of the axoneme. The transition region contains a series of electron dense transverse lamellae rather than a single septum, and lacks a stellate pattern. There is no cartwheel pattern in the proximal part of the basal bodies. The latter are associated with four different types of fibrous elements: ascending striated fibers that attach to an electron dense plate in the papillar center, lateral striated fibers that parallel microtubular roots, fibrous elements that link adjacent basal bodies, and finally two massive striated fibers that descend into the cell, passing closely along the nucleus (system II fibers, or rhizoplasts). Each of the four microtubular flagellar roots is sandwiched between two system I striated structures. The roots are probably equal; they contain proximally four, and distally up to eight microtubules. Based on the zoospore flagellar apparatus, it is concluded that the multinucleate U. penicilliformis is related to the Ulvaphyceae. Finally, a possible explanation in functional terms is given for the peculiar external morphology and behavior of the zoospore.