The flagellar root system inHeterosigma akashiwo (Raphidophyceae)

Summary The flagellar apparatus of 3 isolates ofHeterosigma akashiwo (Hada) Hada has been studied by serial sectioning. The two basal bodies lie at almost right angles to one another, but in a different plane, and are interconnected by an extensive root system. This consists of three roots (i) a massive cross-banded fibrous root (= rhizoplast) which extends from near the proximal ends of both basal bodies to the anterior surface of the nucleus, (ii) a compound microtubular root with a layered structure, associated with the hairy anterior flagellum and extending to the anterior surface and (iii) the rhizostyle which passes between the two basal bodies leading anteriorly to a vesicle in the flagellar groove region and following the nucleus posteriorly terminating deep in the cytoplasm. Both the characteristic arrangement of the basal bodies and the presence of the complex layered structure are characteristic of theRaphidophyceae. The broad microtubular root, however, to which the layered structure is attached, appears to be characteristic of nearly all heterokont algae, fungi and protozoa so far examined. Thus, our findings have important implications on phylogenetic relationships within the heterokonts and lead us to question whether some of the present classes such as theChrysophyceae andXanthophyceae are indeed natural groups.     

Analysis of cytoplasmic microtubules and flagellar roots in the zoospores ofAllomyces macrogynus

Summary Cytoskeletal and flagellar microtubules in the zoospores of the aquatic fungusAllomyces macrogynus are resistant to microtubule depolymerizing drugs. Consequently, we have analyzed the partial composition and organization of microtubules (Mts) in the cytoplasm and flagellar apparatus in the zoospores ofA. macrogynus. Evidence from two-dimensional gel electrophoresis demonstrated the presence of two -tubulin isoforms in axonemal and cytoplasmic Mts. In addition, a monoclonal antibody specific for acetylated -tubulin was used on one-dimensional protein blots to show that acetylated -tubulins are present in isolated zoospore cell bodies and axonemes. Immunofluorescence microscopy observations using this monoclonal antibody demonstrated that flagellar, kinetosomal, and cytoplasmic Mts were labeled. The nature of Mts in the flagellar apparatus was studied ultrastructurally. InA. macrogynus, the flagellar apparatus consists of the kinetosome, rhizopolast (striated flagellar rootlet), axoneme, and 9 sets of triplet Mts which radiate anteriorly from the proximal end of the kinetosome (microtubular rootlet), Analysis of the rhizoplast indicated that this structure does not contain Mts. The rhizoplast, which connects the functional kinetosome with a single, large basal mitochrondrion, consists of four electron-opaque bands. Serial-sectioning indicated that the rhizoplast is always adjacent to kinetosome triplets 1, 2, and 9, and thus lies perpendicular to the plane of flagellar beat. These results suggest that the primary function of the rhizoplast is to organize the kinetosome and mitochondrion with respect to one another and to bias flagellar beat in the appropriate orientation for cell motility.Abbreviations BSA bovine serum albumin - BCA bicinchoninic acid - DS dilute salts - EGTA ethylene glycol-bis-(-aminoethyl ether)-N,N-tetracetic acid - EM electron microscopy - Mes 2-(N-morpholinomethane sulfonic acid - Mt microtubule - NP-40 Nonidet P-40 - 1-D PAGE one-dimensional polyacrylamide gel electrophoresis - PBS phosphate-buffered saline - PMSF phenylmethylsulfonyl fluoride - SDS sodium dodecyl sulfate - 2-D PAGE two-dimensional polyacrylamide gel electrophoresis - Tween-20 polyoxyethylenesorbitan monolaurate     

Transformation of the flagella and associated flagellar components during cell division in the coccolithophoridPleurochrysis carterae

Summary Immunofluorescence microscopy, conventional and high voltage transmission electron microscopy were used to describe changes in the flagellar apparatus during cell division in the motile, coccolithbearing cells ofPleurochrysis carterae (Braarud and Fagerlund) Christensen. New basal bodies appear alongside the parental basal bodies before mitosis and at prophase the large microtubular (crystalline) roots disassemble as their component microtubules migrate to the future spindle poles. By prometaphase the crystalline roots have disappeared; the flagellar axonemes shorten and the two pairs of basal bodies (each consisting of one parental and one daughter basal body) separate so that each pair is distal to a spindle pole. By late prometaphase the pairs of basal bodies bear diminutive flagellar roots for the future daughter cells. The long flagellum of each daughter cell is derived from the parental basal bodies; thus, the basal body that produces a short flagellum in the parent produces a long flagellum in the daughter cell. We conclude that each basal body in these cells is inherently identical but that a first generation basal body generates a short flagellum and in succeeding generations it produces a long flagellum. At metaphase a fibrous band connecting the basal bodies appears and the roots and basal bodies reorient to their interphase configuration. By telophase the crystalline roots have begun to reform and the rootlet microtubules have assumed their interphase appearance by early cytokinesis.Abbreviations CR1, CR2 crystalline roots 1 and 2 - CT cytoplasmic tongue microtubules - DIC differential interference contrast light microscopy - H haptonema - HVEM high voltage transmission electron microscopy - IMF immunofluorescence microscopy - L left flagellum/basal body - M metaphase plate - MT microtubule - N nucleus - R right flagellum/basal body - R1, R2, R3 roots 1, 2, and 3 - TEM transmission electron microscopy     

Fine structure of the flagellar apparatus of gametesin situ and motile zygotes of the green algaUlothrix flacca var.Roscoffensis (Ulotrichales) (Chlorophyta)

Summary This fine structural study ofUlothrix flacca (Dillw.) ThuretRoscoffensis variety (Berger-Perrot), a marineUlothrix, describes in detail the flagellar apparatus configuration of gametesin situ in the gametangia and in motile zygotes. The gametes's flagellar apparatus shows two basal bodies overlapping at their proximal end at a 30° angle, in an 11/5 o'clock configuration or with a counterclockwise absolute orientation. The basal bodies are interconnected by a non-striated band or capping plate. They are wrapped in their proximal part by an electron-dense sheath and obtured by a bilobed terminal cap. A cruciate microtubular root system having a 4-2-4-2 alternation pattern is present. A striated microtubule associated component (S.M.A.C.) or system I fibres accompany the two membered root R₂. The system II fibres or rhizoplasts along with striated bands associated to the microtubular roots, were not observed and are presumed to be absent.In the motile zygotes, the basal bodies are paired in a cruciate pattern. During the fusion process, two basal bodies, one of each pair, slide in a face to face position with a slight displacement into the 11/5 o'clock direction; the other two make a 30° counterclockwise rotation, thus making a 60° angle between the two basal bodies of each pair instead of 30° in the gamete.After comparison with the flagellar apparatus of other green alga gametes, it is concluded that the taxonomic affinities ofUlothrix flacca var.Roscoffensis, lie with theUlvophyceae sensuStewart andMattox 1978.Abbreviations CP capping plate - ER endoplasmic reticulum - G Golgi body - LG lipid globule - M mitochondria - MS presumed mating structure - N nucleus - R ₂,R ₄ microtubular roots - SH sheath - SMAC striated microtubule associated component - TC terminal cap - V vacuole - Ve vesicles in the anterior papilla - 1, 2, 1, 2 basal bodies numerotation     

Flagellar apparatus ultrastructure inMesostigma viride (Prasinophyceae)

The ultrastructure of the flagellar apparatus ofMesostigma viride Lauterborn (Prasinophyceae) has been studied in detail with particular reference to absolute configurations, numbering of basal bodies, basal body triplets and flagellar roots. The two basal bodies are interconnected by three connecting fibers (one distal fiber = synistosome, and two proximal fibers). The flagellar apparatus shows 180° rotational symmetry; four microtubular flagellar roots and two system II fibers are present. The microtubular roots represent a 4-6-4-6-system. The left roots (1s, 2s) consist of 4 microtubules, each with the usual 3 over 1 root tubule pattern. Each right root (1d, 2d) is proximally associated with a small, but typical multi-layered structure (MLS). The latter displays several layers corresponding to the S₁ (the spline microtubules: 5–7), and presumably the S₂—S₄ (the lamellate layers) of the MLS of theCharophyceae. At its proximal origin (near the basal bodies) each right root originates with only two microtubules, the other spline microtubules being added more distally. The structural and positional information obtained in this study strongly suggest that one of the right roots (1d) ofMesostigma is homologous to the MLS-root of theCharophyceae and sperm cells of archegoniate land plants. Thus the typical cruciate flagellar root system of the green algae and the unilateral flagellar root system of theCharophyceae and archegoniates share a common ancestry. Some functional and phylogenetic aspects of MLS-roots are discussed.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

Partial purification of myosin from lily pollen tubes by monitoring with in vitro motility assay

Summary Myosin in pollen tubes ofLilium longiflorum was partially purified, using an in vitro motility assay as a monitor. The main components in the partially purified preparation had molecular masses of 110, 120, and 140 kDa in SDS-PAGE. They became bound to actin filaments in an ATP-dependent manner. Among the components, only that of 120 kDa became bound to ATP and was concluded to be the heavy chain of pollen tube myosin.Abbreviations ATP adenosine-5-triphosphate - DTT dithiothreitol - EB extraction buffer - EGTA ethyleneglycol-bis-(-aminoethylether) N, N, N, N-tetraacetic acid - PAGE polyacrylamide gel electrophoresis - PIPES piperazine-N,N-bis-(2-ethanesulfonic acid) - PMSF phenylmethylsulfonyl fluoride - SDS sodium dodecylsulfate - TBS Tris buffered saline - TEB Tris-EGTA buffer     

The structure of the flagellar apparatus of the swarm cells ofPhysarum polycephalum

Summary Flagellation ofPhysarum polycephalum amoebae (Myxomycete) involves the formation around the two kinetosomes of a flagellar apparatus leading to a modification in the shape of the amoeba and its nucleus. A tridimensional ultrastructural model of the flagellar apparatus is proposed, based upon observation of the isolated nucleo-flagellar apparatus complex. The flagellar apparatus is composed of a non-microtubular structure (the posterior para-kinetosomal structure), five microtubular arrays and two flagella: a long anterior flagellum and a short flagellum directed backwards. The asymmetry of the flagellar apparatus is due mainly to the presence of the posterior para-kinetosomal structure on the right side of the posterior kinetosome and of the two asymmetrical microtubular arrays 3 and 4. Thus, the flagellar apparatus is right-handed. This asymmetry implies also some spatial constraints on two other microtubular arrays (2 and 5). Except in the case of the microtubular array 1 which links the proximal end of the anterior kinetosome to the nuclear membrane, the number of microtubules of each microtubular array seems to be well defined: 39, 5–6, 7–9, and 2+2 for the microtubular arrays 2, 3, 4, and 5 respectively. All the elements of the nucleo-flagellar apparatus complex are linked either directly or indirectly through bridges. Furthermore, the microtubules which composed the microtubular array 3 are linked through bridges while the microtubules of the microtubular arrays 2, 3, and 4 seem to be linked through a reticulate material. All these spatial relationships lead to a great cohesion of the nucleo-flagellar apparatus complex which appears to be a well defined structure. This suggests thatPhysarum amoebal flagellation can be a promising system to study the morphogenesis of an eucaryotic cell.Abbreviations PIPES Piperazine-N,N-bis [2-ethane-sulfonic acid] - EGTA [Ethylenebis(oxyethylenenitrile)]tetraacetic acid - DMSO Dimethyl sulfoxide     

Glossomastix chrysoplasta n. gen., n. sp. (Pinguiophyceae), a new coccoidal, colony-forming golden alga from southern Australia

Glossomastix chrysoplasta gen. et sp. nov. is described from cultures isolated from sandstone rubble, Sorrento Back Beach, Mornington Peninsula, Victoria, Australia. The alga forms wall‐less, coccoidal vegetative cells that congregate in mucilaginous colonies and reproduce by successive bipartition. Plastids have girdle lamellae and partially embedded pyrenoids that are traversed by cytoplasmic channels. Zoospores are uniflagellate and swim poorly; a narrow lingulate pseudopod provides their primary form of motion. The single flagellum, which lacks hairs, a flagellar swelling, and autofluorescence, is the equivalent of the posterior flagellum in other golden algae. The anterior flagellum is absent; the basal body with which it would normally be associated is blind. The flagellar apparatus has two basal bodies, three microtubular roots, and a rhizoplast. The posterior (elder) basal body has a transitional helix that is proximal to the basal plate. Glossomastix chrysoplasta, placed in the Pinguiophyceae on the basis of molecular sequence and biochemical data, shares some ultrastructural features with other members of the class, especially Polypodochrysis teissieri, which has similar zoospores, but it also differs from other pinguiophytes in many respects. Glossomastix chrysoplasta is the pinguiophyte with, on average, the largest cells (exclusive of external materials), and it is the only one with a colonial habit.     

The flagellar apparatus of heteroloboseans

The flagellar apparatus of four heterolobosean species Percolomonas descissus, Percolomonas sulcatus, Tetramitus rostratus, and Naegleria gruberi were examined. P. descissus lives in oxygen-poor water. It is a quadriflagellated cell with a ventral groove. The two pairs of basal bodies are connected to an apical structure from which the peripheral dorso-lateral microtubules and a short striated rhizoplast originate. There is one major microtubular root, R1, which originates from the posterior basal body pair and splits into left and right portions that support the sides of the ventral groove. The anterior pair of basal bodies is associated with a root of four to five microtubules that runs to the left of the groove. This organisation is similar to that previously reported for Psalteriomonas, Lyromonas, and Percolomonas cosmopolitus. Percolomonas sulcatus has two parallel pairs of basal bodies, each of which is associated with a well-developed R1 root. These roots divide to give two distinct left portions and one merged right portion that support the margins of the slit-like ventral groove. Tetramitus rostratus has two pairs of basal bodies, several rhizoplast fibres, and two R1 roots. Each R1 root supports one wall of the ventral groove. Naegleria gruberi may have two pairs of basal bodies, each associated with a microtubular root and one long rhizoplast fibre. From available data, a 'double bikont'-like organisation of the heterolobosean flagellar apparatus is inferred, where both of the eldest basal bodies have largely 'mature' complements of microtubular roots. The cytoskeletal organisation of heteroloboseans is compared to those of (other) excavates. Our structural data and existing molecular phylogenies weaken the case that Percolomonas, Psalteriomonas, and Lyromonas are phylogenetically separable from other heteroloboseans, undermining many of the highest-level taxa proposed for these organisms, including Percolozoa, Striatorhiza, Percolomonada, Percolomonadea, and Lyromonadea.     

The effect of ionic stress on photosynthesis in Dunaliella tertiolecta

A comparison of the effects of ionic stress and an uncoupler on long-term fluorescence transients (the Kautsky effect) in the green alga Dunaliella tertiolecta indicated that the large quenching induced by ionic stress was caused by a pH gradient across the thylakoid membrane. This possiblity was given support by the increase in the slow phase of 3-(3,4-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in algae subjected to ionic stress. Low-temperature fluorescence emission spectra indicated that salt stress enhanced photosystem-I emission in the dark, and a comparison of simultaneous emissions at 695 and 720 nm at room temperature indicated a further increase in photosystem-I emission during the fluorescence transients. Taken together with the decrease in the fast phase of 3-(3,4-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in stressed algae, our results indicate that ionic stress stimulates cyclic electron flow, and that non-cyclic flow is inhibited. The effect of sucrose-induced osmotic stress was similar to, but less marked than, the effects of NaCl and KCl; the effect of decreasing the external salinity was small.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FCCP carbonylcyanide p-trifluoromethoxyphenylhydrazone - PSI, II photosystem I, II     

Development of the flagellar apparatus during the cell cycle in unicellular algae

Summary Recent evidence has shown that algal cells acquire different flagella and a heterogeneous basal apparatus through the prolonged development of these structures over more than one cell cycle. A system for numbering algal flagella and basal bodies, which is based on developmental studies, is discussed along with the various means by which the flagellar/basal body developmental cycle can be determined. We review the information now available on development of the separate components of the flagellar apparatus-this comes particulary from the Chlorophyta and the Chromophyta-and attempt to elucidate any information which may help in phylogenetic comparisons. New data is provided on developmental changes in the cartwheel part of the basal body and basal body-associated connecting fibrils in green algae.Abbreviations Bb basal body - d right (dexter) root - df right fibrils connecting Bb triplets to microtubular and/or fibrous roots - EM electron microscopy - F flagellum - IMF immunofluorescence microscopy - LM light microscopy - NBBC nucleus-basal body connector - s left (sinister) root - sf 3left fibrils connecting Bb triplets to microtubular and/or fibrous roots. See Nomenclature section of Introduction for the numbering of basal bodies and their flagella; the same numbers apply to Bb-associated d and s roots, and df and sf fibrils     

Transformation and development of the flagellar apparatus ofCryptomonas ovata (Cryptophyceae) during cell division

Summary InCryptomonas ovata, long, dorsal flagella are produced which transform during the following cell division into short, ventral flagella. At division there is a reorientation in cell polarity, and the parental basal apparatus, which comprises the basal bodies and associated roots, is distributed to the daughter cells via a complex sequence of events. Flagellar apparatus development includes the transformation of a four-stranded microtubular root into a mature root of different structure and function. Each newly formed basal body nucleates new microtubular roots, but receives a striated fibrous root from a parental basal body. The striated roots are originally produced on the transforming basal body and are transferred to the new basal bodies at each successive division. The development of the asymmetric flagellar apparatus throughout the cell cycle is described.     

ULTRASTRUCTURAL STUDIES ON BIGELOWIELLA NATANS, GEN. ET SP. NOV., A CHLORARACHNIOPHYTE FLAGELLATE

Three isolates from the Provasoli-Guillard National Center for Culture of Marine Phytoplankton at Bigelow Laboratory, previously labeled Pedinomonas sp. and Pedinomonas minutissima from the green algal class Pedinophyceae, have been examined by light microscopy and TEM and shown to belong to the Chlorarachniophyceae, a class of nucleomorph-containing amebae. The three isolates represent the first chlorarachniophycean flagellates to be discovered. The ultrastructure of the cells has been examined in detail, with particular emphasis on the flagellar apparatus, a feature not examined in detail in chlorarachniophytes before. Cells are basically biflagellate, but the second flagellum is represented by a very short basal body only. Flagellar replication has shown this flagellum to be the mature stage, that is, the no. 1 flagellum, whereas the long emergent flagellum is the no. 2 flagellum that shortens into a short basal body during cell division. Mitosis is open with a pair of centrioles at each pole. Emergent flagella are absent during mitosis. Cells may form cysts, and the flagellar basal bodies and part of the flagellar roots are maintained in the cysts. Four microtubular roots emanate from the basal bodies, and the path of one of them is very unusual and very unlike any other known flagellate. No striated roots were observed. Other fine-structural features of the cell include a very unusual type of pyrenoid and a special type of extrusome. Cells are mixotrophic. The three isolates are very similar and are described as Bigelowiella natans , gen. et sp. nov. Ultrastructurally, chlorarachniophytes do not show close relationship to any known group of algae or other protists.     

Identification of the cytokinins in red pine seedlings

Zeatin-9-riboside was identified in shoots and roots of Pinus resinosa by GC-MS analysis of its permethyl derivative. Based on their chromatographic properties on Sephadex LH-20 and C₁₈ HPLC, and their susceptibility to enzymatic degradation, several other cytokinins have been tentatively identified. The basic fraction of both the roots and shoots contained zeatin, whereas the shoots contained dihydrozeatin-O-glucoside and the roots contained zeatin-O-glucoside. Zeatin-9-riboside monophosphate, isopentenyladenosine monophosphate ([9R-5P]iP) and glucosyl phosphate derivatives were detected in the acidic fractions from both roots and shoots. There were equivalent amounts of [9R-5P]iP in both roots and shoots. The presence of equivalent amounts of [9R-5P]iP in both the roots and shots suggests that cytokinin biosynthesis may be occurring in both locations.Abbreviations AMP adenosine-5-monophosphate - BAP benzylaminopurine - BSA bovine serum albumin - BuOH butan-1-ol - CK cytokinin - (diH)Z dihydrozeatin - (diH OG)Z dihydrozeatin-O-glucoside - (diH OG)[9R]Z dihydrozeatin-9-riboside-O-glucoside - DW dry weight - EtOH ethanol - FW fresh weight - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - [9R]iP isopentenyladenosine - [9R-5P]iP isopentenyladenosine monophosphate - MeOH methanol - PVP polyvinylpyrrolidone - RFE rotary film evaporation - TEAB triethyl ammonium bicarbonate - Z zeatin - [9R]Z zeatin-9-riboside - (OG)Z zeatin-O-glucoside - [7G]Z zeatin-7-glucoside - [9R-5P]Z zeatin-9-riboside monophosphate     

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.     

Structure and significance of cruciate flagellar root systems in green algae: Female gametes ofBryopsis lyngbyei (Bryopsidales)

The ultrastructure of the flagellar apparatus in the biflagellate female gametes of the green algaBryopsis lyngbyei has been studied in detail. In the flagellum and basal body, microtubule septations occur in some of the B-tubules. The transition region of the flagellum is extremely long (260–290 nm), exhibits a stellate pattern in cross section but lacks the transverse diaphragm. The two basal bodies form an angle of 180° and overlap at their proximal ends. They are connected by a compound non-striated capping plate. Terminal caps associated with the capping plate partially close the proximal end of each basal body. A cruciate flagellar root system with three different types of microtubular roots is present, i. e. the flagellar apparatus does not show 180° rotational symmetry. One root type contains 2 microtubules which are connected to an elaborate cylindrical structure, presumably a mating structure. The opposite root exhibits 3 microtubules over its entire length and is not associated with a cylindrical structure. In their proximal parts both roots are linked to an underlying crescent body. The other two microtubular roots are probably identical and consist of 4 (or 5) microtubules which show configurational changes. These two identical roots insert into the capping plate and link to the inner side (i. e. the side adjacent to the other basal body) of each basal body, whereas the other two roots attach to the outer sides of each basal body. System I striated fibres are probably associated with each of the four roots, while system II fibres have not been observed. The flagellar apparatus of female gametes ofB. lyngbyei shows many unique features but in some aspects resembles that of ulvalean algae. Functional and phylogenetic aspects of cruciate flagellar root systems in green algae are discussed.     

Fish production in Lake Kariba,reconsidered

Synopsis Revised total and available production, yield and mean biomass per ha were calculated for each species in Lake Kariba, and for the whole lake. The revision was undertaken because (1) the original value 1 g for W₀ for each species was too high, (2) B_i+1 was occasionally used instead of B_i in the calculation of mean biomass for an interval i to i + 1, and (3) species' contributions to mean parameter values for the whole lake were not weighted according to their mean standing crop. Revised values are, A = 1224, P = 720, Y_A = 400, Y_{Pp, = 202 and B} = 827 kg ha^–1y–1. These correspond to 38.2%, 66.7%, 107.1% and 25.8% respectively of the values calculated initially.     

THE FLAGELLAR APPARATUS OF CHRYSOLEPIDOMONAS DENDROLEPIDOTA (CHRYSOPHYCEAE), A SINGLE-CELLED MONAD COVED WITH ORGANIC SCALES1

The flagellar apparatus of Chrysolepidomonas dedrolepidota Peters et Andersen is similar to that of other members of the Ochromonadales, Chrysophyceae. there are four microtubular roots (R_1-4) and a system II fiber (= rhizoplast). the R₁ root consists of three microtubules that nucleate many cytoplasmic microtubules. One compressed band of 10 or more cytoplasmic microtubules is directed black along the R1 root in an anti-parallel direction. The R₂ root consists of one to two microtubules, and it extends toward the distal end of the R₁ root. The R₃ root consists of six (?seven) microtubules near its proximal end. The “a” and “f” microtubules of the R₃ root are under the short flagellum, and the “f” microtubule loops back and under the basal body, extending down to the nucleus. The R₄ root consists of one to two microtubules extending along the left side of the shot flagellum and curving under the short flagellum where it terminates near the “a” microtubule of R₃ Both flagella have a transitional plate and a transitional helix with five gyres. There is a thin, second plate in the basal body at the level of the distal end of the “c” tubules of the basal body triplets. The tripartite flagellar hairs have long lateral filaments but lack short lateral filaments. We compare the flagellar apparatus with that of other members of the Ochromonadales and members of the Hydrurales and Hibberdiales.     

Behavior of flagella and flagellar root systems in the planozygotes and settled zygotes of the green alga Bryopsis maxima Okamura (Ulvophyceae,Chlorophyta) with reference to spatial arrangement of eyespot and cell fusion site

Behaviors of male and female gametes, planozygotes and their microtubular cytoskeletons of a marine green alga Bryopsis maxima Okamura were studied using field emission scanning electron microscopy, high‐speed video microscopy, and anti‐tubulin immunofluorescence microscopy. After fusion of the biflagellate male and female gametes, two sets of basal bodies lay side by side in the planozygote. Four long female microtubular roots extended from the basal bodies to the cell posterior. Four short male roots extended to nearly half the distance to the posterior end. Two flagella, one each from the male and female gametes, become a pair. Specifically, the no. 2 flagellum of the female gamete and one male flagellum point to the right side of the eyespot of the female gamete, which is located at the cell posterior and which is associated with 2s and 2d roots of the female gamete. This spatial relationship of the flagella, microtubular roots, and the eyespot in the planozygote is retained until settlement. During forward swimming, the planozygote swings the flagella backward and moves by flagellar beating. The male and female flagella in the pair usually beat synchronously. The cell withdraws the flagella and becomes round when the planozygote settles to the substratum 20 min after mixing. The axoneme and microtubular roots depolymerize, except for the proximal part and the basal bodies. Subsequently, distinct arrays of cortical microtubules develop in zygotes until 30 min after mixing. These results are discussed with respect to the functional significance of the spatial relationships of flagellar apparatus‐eyespot‐cell fusion sites in the mating gametes and planozygote of green algae.