中国海区几种隐藻类鞭毛藻的扫描电镜观察

报道了来自香港吐露港、中国长江口及厦门港的3个属的3种隐藻及1个变种, 即半片藻Hemiselmis sp. Novarino、伸长斜片藻Plagioselmis prolonga Butcher ex Novarino, Lucas ＆ Morrall、伸长斜片藻北方变种Plagioselmis prolonga var. nordica Novarino, Lucas ＆ Morrall、尖尾全沟藻Teleaulax acuta （Butcher） Hill, 并对每个种类的分类特征、生态分布进行描述, 同时提供每个种的光镜和扫描电镜照片。其中, 半片藻属Hemiselmis Parke是中国海区首次记录的属, 而伸长斜片藻Plagioselmis prolonga和尖尾全沟藻Teleaulax acuta可以引发赤潮。     

Pole reversal and the development of cell asymmetry during division in cryptomonad flagellates

Summary A unique form of cell division is reported for the cellsKomma caudata andCryptomonas ovata (Cryptophyceae). During cytokinesis, the posterior tail-like region of each daughter cell develops from the anterior region of the parental cell. This process, termed pole reversal, involves a major realignment in overall cell polarity as well as alterations to cytoplasmic and surface components. Pole reversal may be a consequence of flagellar apparatus transformation and reorientation during division, and pole reversal may facilitate the development of the asymmetric cell shape in daughter cells.     

Cytokinesis inCryptomonas ovata (Cryptophyceae)

Summary We describe the pattern of cytokinesis inCryptomonas ovata. Cell division begins at the posterior of an enlarged cell and proceeds through the gullet and between four active flagella. This pattern of cytokinesis inCryptomonas ovata differs from that previously described for other cryptomonads and might be of importance in establishing taxonomic affinities for the group.     

Temperature × light interaction and tolerance of high water temperature in the planktonic freshwater flagellates Cryptomonas (Cryptophyceae) and Dinobryon (Chrysophyceae)

Using microcosm experiments, we investigated the interactive effects of temperature and light on specific growth rates of three species each of the phytoplanktonic genera Cryptomonas and Dinobryon. Several species of these genera play important roles in the food web of lakes and seem to be sensitive to high water temperature. We measured growth rates at three to four photon flux densities ranging from 10 to 240 μmol photon · m^?2 · s^?1 and at 4–5 temperatures ranging from 10°C to 28°C. The temperature × light interaction was generally strong, species specific, and also genus specific. Five of the six species studied tolerated 25°C when light availability was high; however, low light reduced tolerance of high temperatures. Growth rates of all six species were unaffected by temperature in the 10°C–15°C range at light levels ≤50 μmol photon · m^?2 · s^?1. At high light, growth rates of Cryptomonas spp. increased with temperature until the temperature optimum was reached and then declined. The Dinobryon species were less sensitive than Cryptomonas spp. to photon flux densities of 40 μmol photon · m^?2 · s^?1 and 200 μmol photon · m^?2 · s^?1 over the entire temperature range but did not grow under a combination of very low light (10 μmol photon · m^?2 · s^?1) and high temperature (≥20°C). Among the three Cryptomonas species, cell volume declined with temperature and the maximum temperature tolerated was negatively related to cell size. Since Cryptomonas is important food for microzooplankton, these trends may affect the pelagic carbon flow if lake warming continues.     

Indirectly fluorescently labelled flagellates (IFLF): a tool to estimate the predation on free-living heterotrophic flagellates

A procedure was developed to estimate the direct grazing impacton free-living heterotrophic nanoflagellates (HNF). Culturedflagellates were labelled by feeding on brightly fluorescingbacteria (FLB) and then offered as indirectly fluorescentlylabelled flagellates (IFLF) to potential predators of HNF. Thenumber of FLB in the predators' food vacuoles could be convertedinto IFLF uptake and consumption of HNF. This new techniquewas used to study the HNF-ciliate relationship in the pelagiczone of Lake Constance. Three groups of ciliates were detectedas HNF grazers: small representatives of the genus Strobilidium.a small Haltena-like ciliate (probably Halteria grandinella)and a Codonella sp. Tintinnidium sp. group The ingestion ofHNF by these groups of ciliates ranged between 3 and 15, 3 and39, and 3 and 7 HNF ciliate^–1 h^–1; respectively.The IFLF method allows the direct determination of ingestedflagellate prey in the food vacuoles of their predators. Becauseindigenous living prey organisms were used, tracer discriminationcan be reduced.     

The ultrastructure of mitosis inChroomonas salina (Cryptophyceae)

Summary A detailed account of the ultrastructure of mitosis in a member of theCryptophyceae is given for the first time. The initial indication of mitosis is the duplication of the flagellar bases. The nucleus migrates towards the anterior of the cell and its envelope and nucleolus break down. The chromatin which at interphase is in the form of scattered clumps, condenses into a solid mass through which run narrow tunnels. Each tunnel allows the passage of one to four microtubules. At metaphase the dense plate of chromatin is situated on the equator and the spindle has a rectangular shape. Individual chromosomes cannot be recognized and no morphologically differentiated kinetochores have been observed. The flagella remain functional, their bases stay at the anterior side of the nucleus and do not move to the poles. At anaphase two plates of chromatin separate and these move apart until they come to lie against the ER sheath surrounding the chloroplasts. The new nuclear envelope starts to form on the opposite side of the daughter nucleus. Cytokinesis may commence early in mitosis and consists of a constriction of the parent cell, starting from the posterior end, followed by separation of the two daughters. The present work supports earlier views that only one chromosome is evident during the nuclear division of these organisms. The mitosis is completely different from that of theDinophyceae with which theCryptophyceae were formerly linked.     

Lectin binding in Cryptomonas and Chroomonas (Cryptophyceae)

The cell envelopes of Cryptomonas and Chroomonas exhibited significant fluorescence using FITC-labelled concanavalin A and wheat germ agglutinin when the cells were fixed prior to lectin binding. The periplast became intensely labelled in Chroomonas whereas Cryptomonas showed fluorescing granula in its gullet/furrow region and on the cell surface. Lectin labelling followed by fixation showed only label of periplast remnants of lysed cells and of the flagella of Chroomonas. Isolated periplasts of Cryptomonas and Chroomonas were intensively labelled with both concanavalin A and wheat germ agglutinin. Glycostaining of gels, onto which total cell protein extracts were loaded, showed a glycoprotein of high molecular weight for Cryptomonas and Chroomonas and an additional glycoprotein for Cryptomonas species.     

The ultrastructure of Chroomonas mesostigmatica Butcher (Cryptophyceae)

Summary The detailed fine structure of a pigmented marine member of the Cryptophyceae is reported for the first time. The flagella are similar to those of other cryptomonads which have been studied but the root system is probably less complicated. The ejectosomes (trichocysts) have the typical structure but are present in fewer numbers than in many other members of the class. The chloroplasts contain numerous lamellae each composed of two rather dense thylakoids. A single large pyrenoid is attached to a chloroplast and on a short spur beyond this is the centrally placed eyespot. The chloroplasts, pyrenoid and eyespot are all enclosed by an endoplasmic reticulum sheath and starch grains are laid down between this sheath and the chloroplasts. The interphase nucleus is irregular in shape but has the typical eucaryotic appearance. At the anterior end of the cell are numerous coated vesicles which may have an excretory function. The fine structure of Chroomonas is discussed in relation to the ultrastructure of other algae.

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Zusammenfassung Zum ersten Male wird der Feinbau einer Cryptomonadacee des Meers in seinen Einzelheiten geschildert. Die Geißeln gleichen denen der anderen, bisher untersuchten Cryptomonaden; nur die Art der Einfügung ist vielleicht etwas einfacher. Die Ejectosomen (Trichocysten) haben die übliche Struktur, sind aber weniger zahlreich als bei den anderen Mitgliedern der Familie und Klasse. Die Chromatophoren enthalten zahlreiche Lamellen, deren jede aus zwei ziemlich dichten Thylakoiden zusammengesetzt ist. Ein einzelnes pyrenoid sitzt an den Chromatophoren. Ein zentraler Augenfleck ist an einem kurzen Fortsatz derselben befestigt. Chromatophoren, Pyrenoid und Augenfleck sind gemeinsam von einer endoplasmatischen netzigen Hülle (endoplasmatisches Reticulum) umhüllt. Zwischen dieser Hülle und den Chromatophoren werden Stärkekörner abgelagert. Der Zellkern ist in der Interphase unregelmäßig gestaltet. Er hat das übliche Aussehen der eukaryotischen Lebewesen. Am Vorderende sind zahlreiche umhüllte Bläschen, die wohl Abscheidungsorganellen sind. Der Feinbau von Chroomonas wird mit dem anderer Algen verglichen.

     

A comparative study of periplast structure inCryptomonas cryophila andC. ovata (Cryptophyceae)

Summary Freeze-fracture followed by deep-etch was used with transmission electron microscopy to characterize and compare the periplasts of two cryptomonads,Cryptomonas ovata andC. cryophila. The periplast ofC. ovata consists of a dense surface mat of granular/fibrillar material overlying a series of polygonal plates attached to the undersurface of the plasma membrane (PM) at their upturned edges. Fracture faces of the PM reveal a highly stable substructure with distinct patterns of intra-membrane particles (IMPs) associated with the underlying plates; a role for the PM in plate development is indicated. The surface periplast component ofC. cryophila exhibits a cover of morphologically complex, overlapping heptagonal scales (termed rosette scales) in addition to elongate fibrils. The arrangement of IMPs within the PM is predominantly random and the inner periplast component consists of a sheet with regular pores where ejectisomes are located. The sheet does not appear closely associated with the PM. The combination of features exhibited by the periplast ofC. cryophila warrants its inclusion as a new type within theCryptophyceae.     

Energy transfers from Photosystem II to Photosystem I in Cryptomonas rufescens (Cryptophyceae)

In Cryptomonas rufescens (Cryptophyceae), phycoerythrin located in the thylakoid lumen is the major accessory pigment. Oxygen action spectra prove phycoerythrin to be efficient in trapping light energy.The fluorescence excitation spectra at ?196°C obtained by the method of Butler and Kitajima (Butler, W.L. and Kitajima, M. (1975) Biochim. Biophys. Acta 396, 72–85) indicate that like in Rhodophycease, chlorophyll a is the exclusive light-harvesting pigment for Photosystem I.For Photosystem II we can observe two types of antennae: (1) a light-harvesting chlorophyll complex connected to Photosystem II reaction centers, which transfers excitation energy to Photosystem I reaction centers when all the Photosystem II traps are closed. (2) A light-harvesting phycoerythrin complex, which transfers excitation energy exclusively to the Photosystem II reaction complexes responsible for fluorescence at 690 nm.We conclude that in Cryptophyceae, phycoerythrin is an efficient light-harvesting pigment, organized as an antenna connected to Photosystem II centers, antenna situated in the lumen of the thylakoid. However, we cannot afford to exclude that a few parts of phycobilin pigments could be connected to inactive chlorophylls fluorescing at 690 nm.     

Periplaststruktur und Organisation der Plasmamembran vonRhodomonas spec. (Cryptophyceae)

Summary The periplast of the CryptophyceaeRhodomonas has a hexagonal substructure. This substructure is caused by periplast plates. In freeze fracture replicas of the plasma membrane, there are corresponding hexagonal areas with numerous particles. These areas are separated by regions with less particles. Aggregates of particles, partly rosette-like, indicate insertion sites of ejectisomes.

     

Structure and development of the cryptomonad periplast: A review

Summary The structure and development of the complex periplast, or cell covering, of cryptomonads is reviewed. The periplast consists of the plasma membrane (PM) plus an associated surface periplast component (SPC) and cytoplasmic or inner periplast component (IPC). The structure of the SPC and IPC, and their association with the PM, varies considerably between genera. This review, which concentrates on cryptomonads with an IPC of discrete plates, discusses relationships between periplast components and examines the development of this unique cell covering. Formation and growth of inner plates occurs throughout the cell cycle from specialized regions termed anamorphic zones. Crystalline surface plates, which comprise the SPC in many cryptomonad species, appear to form by self-assembly of disorganized subunits. InKomma caudata the subunits are composed of a high molecular weight glycoprotein that is produced within the endomembrane system and deposited onto the cell surface within anamorphic zones. The self-assembly of subunits into highly ordered surface plates appears closely associated with developmental changes in the underlying IPC and PM.     

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.     

Observations on the ultrastructure of representatives of the genera Hemiselmis and Chroomonas (Cryptophyceae)

Hemiselmis rufescens Parke and three species of the genus Chroomonas have been examined by electron microscopy. They demonstrate certain characteristic features of the Cryptophyceae, such as the presence of trichocysts and the arrangement of thylakoids in pairs in the plastid. The prominent pyrenoid of the genus Chroomonas is penetrated longitudinally by a tongue of cytoplasmic matrix which originates from between the two pairs of plastid membranes. In the genus Hemiselmis, however, the pyrenoid is traversed by a pair of thylakoids. The nucleus, Golgi apparatus and Corps de Maupas also occupy characteristic positions. These features indicate a close relationship between these two genera and the other major genus Cryptomonas, and support the suggestion that the Cryptophyceae is a discrete taxonomic group.