Studies on the ultrastructure and taxonomy of the genusTetraselmis (Prasinophyceae)

Comparative ultrastructural investigations on many isolates ofTetraselmis from Japan and the Pacific coast of North America, and on cultures from the Culture Centre of Algae and Protozoa, Cambridge, England, have revealed that the species have characteristic fine structural features of the pyrenoid. Using the pyrenoid structure as a basic character it is proposed that the genus be subdivided into four subgenera,Tetraselmis, Prasinocladia, Tetrathele andParviselmis. In the present paper, species of the subgenusTetraselmis, includingT. cordiformis, T. ascus, T. convolutae andT. astigmatica sp. nov., are described in detail.     

Studies on the ultrastructure and taxonomy of the genusTetraselmis (Prasinophyceae)

Journal of Plant Research - Parviselmis is described as the third subgenus ofTetraselmis (Prasinophyceae) on the basis of the ultrastructural features of pyrenoid. This subgenus is characterized by...     

Morphology and ultrastructure ofOlisthodiscus luteus (Raphidophyceae) with special reference to the taxonomy

A flattened discoid flagellate collected from the Seto Inland Sea, Japan, has been examined by light and electron microscopy. This alga agrees well withClisthodiscus luteus Carter. It has two heterodynamic flagella emerging from a furrow on the upward side of the cell that contains six to 13 yellow-green parietal chloroplasts. It does not rotate but smoothly glide while swimming. The cell has a thin periplast lying between the plasmalemma and chloroplasts. Neither lipid bodies nor mucocysts are seen in the periplast. The pyrenoid matrix being free from thylakoids is penetrated by several cytoplasmic canals from various directions. There are no vesicles of periplastidal network in the narrow space between chloroplast envelope and chloroplast ER. The ultrastructural features ofO. luteus are unique, sharing certain characters with the raphidophycean algae but others withPseudopedinella pyriformis, a unique member of the Chrysophyceae.     

Morphology,ultrastructure and taxonomy of the raphidophycean algaHeterosigma akashiwo

Heterosigma akashiwo and its related algae were re-examined by light and electron microscopes using cultured materials including type cultures of bothH. akashiwo andH. inlandica as well as specimens referred to asOlisthodiscus luteus maintained in CCAP and UTEX. All the strains examined were similar to one another in appearance and ultrastructural features. They can be accommodated in a single species,H. akashiwo, which has been invalidly published. In this paper, the genus is validly desribed by providing a Latin diagnosis and designating a type species. Ultrastructural characteristics are also given for the genus.     

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.     

Laboratory culture and taxonomy ofHymenomonas coronata andOchrosphaera verrucosa (Class Prymnesiophyceae) from the Northwest Pacific

Hymenomonas coronata andOchrosphaera verrucosa, both members of the coccolithophorids, Class Prymnesiophyceae, have been studied by means of electron microscopy and with the aid of laboratory culture. Living specimens of these two species were collected in temperate and subtropical regions of Japan, including the Kii Peninsula and the Ryukyu Islands, and unialgal cultures were established in the laboratory. Their life histories are fundamentally identical, and consist of a non-motile vegetative stage that produces motile cells. The vegetative stage is either unicellular, or a packet consisting of a few cells. Both the non-motile cells and the motile cells are covered with two kinds of scales: these are thin scales of unmineralized nature and coccoliths. These two species differ from each other in the shape of the coccoliths and in the presence or absence of visible rudimentary haptonema, and they have been in separate families. The present study reveals that both species are fundamentally identical in the structure and the distribution of major organelles, especially with respect to two opposed pyrenoids which bulge from chloroplasts, each being traversed by two thylakoid bands, and a group of microtubules forming a flagellar root. On the basis of these characteristics, it would appear more logical to place these two species in the same family, namely the Hymenomonadaceae.     

Isolation,purification, and characterization of flagellar scales from the green flagellateTetraselmis striata (Prasinophyceae)

Summary Flagellar scales from the green flagellateTetraselmis striata (Prasinophyceae) were isolated, purified by isopycnic cesium chloride-gradient and zonal sucrose gradient centrifugation and their structure and biochemical composition investigated. Three types of flagellar scales were purified to more than 90% purity, a fourth type up to 75% purity. In addition to the previously known types of flagellar scales (pentagonal scales, rod-shaped scales, hair-scales), a novel scale type (i.e., the knotted scales) was discovered. New information about the asymmetric structure of the rod-shaped scales is presented and consequently they are renamed man scales. Flagellar scales consist mainly of carbohydrate (50–70%), significant amounts of protein (11% of dry weight) were found only in pentagonal scales. The main sugars (90%) of the pentagonal and man scales are the unusual 2-keto-sugar acids 3-deoxy-5-O-methyl-2-octulosonic acid (5 OMeKDO), 3-deoxy-2-heptulosaric acid (DHA), and 3-deoxy-2-octulosonic acid (KDO), the knotted scales contain as major sugars galactose and arabinose in addition to KDO and 5 OMeKDO but lack DHA. 13 major polypeptides were identified in flagellar scales by one-dimensional SDS-PAGE, 11 of these are of high molecular mass (>116 kDa). While the majority of polypeptides was found associated with pentagonal scales, at least 4 polypeptides were tentatively assigned to the hair-scales and knotted scales.Abbreviations CSF crude scale fraction - PS pentagonal scales - MS man scales - HS hair-scales - KS knotted scales - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - DHA 3-deoxylyxo-2-heptulosaric acid - 5 OMeKDO 3-deoxy-5-O-methyl-manno-2-octulosonic acid - KDO 3-deoxy-manno-2-octulosonic acid - GA Golgi apparatus     

Physical map and gene organization of the mitochondrial genome from the unicellular green alga Platymonas (Tetraselmis) subcordiformis (Prasinophyceae)

the entire mitochondrial genome (mt genome) of the unicellular green alga Platymonas subcordiformis (synonym Tetraselmis subcordiformis; Prasinophyceae) was cloned and a physical map for the four restriction enzymes Hind III, Eco RI, Bgl II and Xba I was constructed. The mt genome of P. subcordiformis is a 42.8 kb circular molecule, coding for at least 23 genes. Hybridization and sequence analysis revealed the presence of a ca. 1.5 kb inverted repeat on the mt genome of P. subcordiformis. Phylogenetic analyses based on sequences of several coxI genes were carried out. Our data indicate that mitochondria from P. subcordiformis and from land plants form a natural, monophyletic group.     

Studies on ammonium-assimilating enzymes of Platymonas striata Butcher (Prasinophyceae)

Platymonas striata Butcher displays significant levels of glutamate synthase (GS) (EC 2.6.1.53) and glutamine synthetase (GOGAT) (EC 6.3.1.2.), but very low levels of glutamate dehydrogenase (GDH) (EC 1.4.1.4). This suggests that the GS/GOGAT pathway is important for nitrogen assimilation. The in vitro rates of enzyme activity can however only account for about 10% of the in vivo rates of nitrogen assimilation. Nitrogen-starvation reduced GS activity to undetectable levels. On nitrate or ammonium ion refeeding the cellular GS activity was rapidly restored, and reached levels of 56% and 91% greater than the unstarved values 24h after refeeding nitrate or ammonium respectively.Abbreviations NAR nitrate reductase - NIR nitrate reductase     

The ultrastructure and calcification of the scales of Tilapia mossambica (Peters)

Summary The scales of Tilapia are surrounded by an envelope of scleroblasts responsible for the production of layers of collagen that constitute the bulk of the scale. The scleroblasts adjoining the lateral face of the oldest scale region gradually atrophy. New collagen layers are deposited against the inner face of the scale, the adjoining scleroblasts showing evidence of high metabolic activity. Calcification occurs by inotropic deposition of crystals alongside the fibres. There is no sharp demarcation between calcified and non-calcified scale regions, a calcification front gradually moving towards newly formed collagen layers. It is felt that fish scales should be considered as calcified derivatives of dermal collagen layers.     

A new point of view on the taxonomy ofPottia starckeana agg. (Musci,Pottiaceae)

A new taxonomic treatment is proposed for thePottia starckeana species complex. The peristome development is not considered to be a useful feature to separate the taxa. On the basis of spore morphology only two species are accepted:P. starckeana, with spores wavy in outline, andP. davalliana, with variously-shaped and developed processes on the spores.Pottia starckeana var.brachyoda is reduced to synonymy withP. starckeana; P. conica andP. commutata are treated as synonyms ofP. davalliana. The speciesP. mutica, P. affinis, P. salina, P. microphylla, P. texana, andP. arizonica (included var.mucronulata) are considered taxa of doubtful affinity, as they have spore features intermediate between the two spore types established for the group. The identity ofP. appertii andP. recurvifolia has not been elucidated because the type material has been destroyed.     

Morphology and taxonomy of chain-forming species of the genus Cochlodinium (Dinophyceae)

The morphology of an unarmored chain-forming harmful dinoflagellate Cochlodinium polykrikoides and its similar species such as Cochlodinium catenatum, Cochlodinium fulvescens, and Cochlodinium convolutum was carefully observed, emphasizing the single cell stage for clarifying taxonomically important morphological features. To differentiate C. polykrikoides from C. convolutum, the shape and the position of the nucleus are useful characters. C. polykrikoides also differs from C. fulvescens in being smaller in size, possessing many rod-shaped chloroplasts and having the sulcus running just below the cingulum on the dorsal surface. Careful observation of the ichnotype of C. catenatum suggests that C. catenatum sensu Kofoid and Swezy collected from off La Jolla, CA, USA, is not identical to C. catenatum sensu Okamura and is probably a different species, in having no chloroplasts and a nucleus positioned at the center of the cell. In addition, C. polykrikoides has many morphological features in common with C. catenatum sensu Okamura except for slightly elongate cells and is probably a junior synonym of this species.     

中国毛茛科翠雀属的分类学研究(八):短尾翠雀花的名实订正

发现近来根据云南西北部丽江标本描述的毛茛科短尾翠雀花(Delphinium brachyurum W. T. Wang)与此前根据该地标本描述的丽江翠雀花(D. likiangense Franch.)属于同一种植物,故将前者处理为后者的异名。     

中国毛茛科翠雀属的分类学研究(十三):狭序翠雀花的名实订正

发现根据甘肃南部标本描述的毛茛科狭序翠雀花（Delphinium angustipaniculatum W.T.Wang）与此前记载分布于甘肃南部和四川北部的松潘翠雀花（D.sutchuenense Franch.）属于同一种植物,故将前者处理为后者的异名。讨论了松潘翠雀花与其可能的近缘种秦岭翠雀花（D.giraldii Diels）和疏花翠雀花（D.sparsiflorum Maxim.）的形态区别。     

The ultrastructure of the sinus gland of the crayfish Astacus leptodactylus (Nordmann)

Summary An ultrastructural study of the sinus gland of the crayfish Astacus leptodactylus demonstrates that this gland is mainly composed of glial cells, axons and axon terminals. On the basis of the size, shape and electron density of the neurosecretory granules, we could distinguish five different types of axon terminals.     

Comparative ultrastructure of the zoospores of nine species ofNeochloris (Chlorophyta)

Nine species ofNeochloris can be divided into three groups on the basis of comparative ultrastructure of the flagellar apparatus, the cell wall and the pyrenoid of zoospores. In Group I,N. wimmeri andN. minuta, zoospores are thin-walled, pyrenoids are penetrated by stromal channels, and the basal bodies are in the clockwise absolute orientation and connected by the distal and two proximal fibers. In Group II,N. aquatica, N. vigenis, N. terrestris, N. pyenoidosa, andN. pseudostigmatica, zoospores are naked or covered by fuzzy material, pyrenoids are covered by a continuous starch sheath or invaginated by cytoplasmic channels, basal bodies are directly opposed, the distal fiber is differentiated into a ribbed structure at the central region, a striated microtubule-associated component (SMAC) is continuous between opposite two-membered rootlets and connected to the ribbed structure, proximal ends of basal bodies are covered by partial caps, each two-membered rootlet and a basal body are connected by a striated fiber to the X-membered rootlet associated with the opposite basal body, and the basal bodies, when oriented at wide angles, are joined at their proximal ends by core extensions. In Group III,N. pseudoalveolaris andN. cohaerens, zoospores are naked, pyrenoids are traversed by parallel thylakoids, basal bodies are in the counterclockwise absolute orientation and overlapped, and each X-membered rootlet is connected to the end of the opposite basal body by a terminal cap. It is suggested that the genusChlorococcopsis gen. nov. be erected for the Group I species. Group II, which includes the type species,N. aquatica, should be preserved asNeochloris. The group appears to be closely related to the coenobial generaPediastrum, Hydrodictyon, andSorastrum, and to have affinities with the coenocytic generaSphaeroplea andAtractomorpha as well. It is also suggested that the genusParietochloris gen. nov. be erected in thePleurastrophyceae for the species of Group III.     

Ultrastructure and freeze-fracture studies of the thylakoids ofMantoniella squamata (Prasinophyceae)

Summary The ultrastructure and the supramolecular organization of the thylakoids of the small green flagellate,Mantoniella squamata, were examined in thin sections and freeze-fracture preparations. The whole chloroplast is tightly packed with thylakoids, which show a pattern of meandering, branching and/or anastomosing membranes. In freeze-fracture preparations only two fracture-faces can be distinguished: the PF- and the EF-face. The PF-face has a much higher particle density than the EF-face (PF: 4086 particles/m²; EF: 865 particles/m²). The EF-face is not as uniform as the PF-face. The areas which are packed with particles probably correspond to closely appressed thylakoid regions or adhesive patches, noticed in thin sections in some areas. The mean particle size on both faces is also different (EF: 10.5 nm; PF: 8.6 nm), but no information about the classification of the particles to special protein complexes is available at this time.Abbreviations chl chlorophyll - EF exoplasmic fracture face - ER endoplasmic reticulum - LHC light-harvesting chlorophyll-protein complex - PF protoplasmic fracture face - PS I photosystem I - PS II photosystem II     

The ultrastructure of the sinus gland of Gammarus oceanicus (Crustacea: Amphipoda)

Summary The sinus gland of Gammarus oceanicus, like that of other crustaceans, is composed of three elements: neurosecretory axons, glial cells and stromal sheath. Five neurosecretory axon types are identified on the basis of granule diameter, shape, and electron density, and axon matrix density. Exocytosis appears to be the major release mechanism of neurosecretory material. The preterminal regions of neurosecretory axons contain axoplasmic reticulum and neurotubules. Their arrangement in the axon and relationship with one another suggest a transport function. Multilamellar bodies are found in the terminal regions of neurosecretory axons. They arise from mitochondria and may be involved in granulolysis.The technical assistance of G.A. Bance, statistical assistance of D. MacCharles and D.W. Hagen, and financial support provided by the University of New Brunswick Research Fund to K.H. are gratefully acknowledged     

中国毛茛科翠雀属的分类学研究(十二):竞生翠雀花的名实订正

通过标本室和野外观察,发现根据云南西北部中甸标本描述的毛茛科竞生翠雀花（Delphinium yangii W.T.Wang）与此前记载分布于该地及四川西南部（康定、小金、汶川）的宝兴翠雀花（D.smithianum Hand.-Mazz.）属于同一分类实体,故将前者处理为后者的异名。