摘要:

ABSTRACT.Many advances have been made in our knowledge of the biology of foraminifera over the past several decades. Fine structural, biophysical, and molecular biological studies have shown that the most prominent components of their distinctive bidirectional granuloreliculopods are bundles of micro tubules linked by crossbridges to each other, as well as to membrane‐bound organelles and the plasma membrane. the microtubules ratchet past each other as dynein transduces the free energy of ATP to produce pseudopodal movements. In spite of the fact that there are over 40,000 described species of living and fossil species of foraminifera, there have been many recent exciting discoveries of new species and groups. New casting techniques are providing us with greater understanding of the complexities and functional aspects of form in the group. Significant advances are being made in understanding the distribution and energetics of deep‐sea forms. Larger and planktonic foraminifera are the hosts for a particularly diverse range of endosymbiotic algae, including dinoflagellates, chlorophytes, unicellular rhodophytes, and diatoms. Chloroplast husbandry also occurs. Significant research effort has been expended yielding us considerable insight into various aspects of the endosymbiotic phenomenon. A unified conceptual framework has been drawn to help us understand the life cycle options found in foraminif

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04934.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Several domains of large subunit rRNA from nine trichomonad species have been sequenced. Molecular phylogenies obtained with parsimony and distance methods demonstrate the trichomonads are a monophyletic group which branches very early in the eukaryotic tree. the topology of the trees is in general agreement with traditional views on evolutionary and systematic relationships of trichomonads. A clear dichotomy is noted between the subfamily Trichomonadinae and the subfamily Tritrichomonadinae. In the latter subfamily, a second division separates the “Tritrichomonas muris‐type” species from the “Tritrichomonas augusta‐type” ones. Previous evolutionary schemes in which the Monocercomonadidae were regarded as the most “primitive” and the Trichomonadidae as more “evolved” are not in agreement with our molecular data. the emergence ofMonocercomonasandHypotrichomonasat the base of theTritrichomonaslineage suggests a secondary loss of some cytoskeletal structures, the costa and undulating membrane in these genera. This is corroborated by the early branching position ofTrichomitus.which possesses a costa and an undulating membrane and has usually been placed among the Trichomonadidae on the basis of cytological characters. A cladistic analysis was applied to the available morphological characters in order to produce a hierarchical grouping of the taxa reflecting their morphological diversity. Supplementary key words. Evolution, molecular phylogeny, morphological

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04935.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Two new hemimastigophoran flagellates are described using light and electron microscopy, and the family Spironemidae is revised.Spironema terricolan. sp. occurs in soil from the Grand Canyon (southwest USA). It moves in a conspicuously euglenoid manner and differs fromS. multiciliatumKlebs by its vermiform shape and shorter kinetics.Spironema terricolais similar to Goodey'sSpironema multiciliatumfrom soil in England. However, Goodey's vermiform species has a very elongate nucleus and is thus neither identical withS. terricola, which has a roundish nucleus, nor with Klebs' lanceolateS. multiciliatum; we consider it a new species,Spironema goodeyin. sp,Stereonema geiserin. g., n. sp. was discovered in the Aufwuchs (periphyton) of a river in Bavaria, Germany. the new genus differs fromSpironemaby its a contractility, and fromHemimastixby its shorter kinetics and less plicate cortex. the fine structure ofSpironemaandStereonemais very similar to that ofHemimastixFoissner et al., viz., the cortex is composed of two plates having diagonal symmetry and the flagellated basal bodies have associated a short and a long microtubular ribbon. All species have unique extrusomes of the same type. the main differences between the three genera and five species recognized are contractility, length of kinetics, body size, shape of cell and nucleus, and particulars of the cortex and extrusomes. the phylogenetic relationships of the Hemimastigophora are still uncertain. However, the diagonal symmetry of the cortical plates and the pronounced euglenoid movement ofSpironemaspp. suggest a common ancestor with euglenids.

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04936.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.A cell culture ofParameciumwith a precise negative gravitaxis was exposed to 4 times 10‐6gduring a parabolic flight of a sounding rocket for 6 min. Computer image analysis revealed that without gravity stimulus the individual swimming paths remained straight. In addition, three reactions could be distinguished. For about 30 s, paramecia maintained the swimming direction they had before onset of low gravity. During the next 20 s, an approximate reversal of the swimming direction occurred. This period was followed by the expected random swimming pattern. Similar behavior was observed under the condition of simulated weightlessness on a fast‐rotating clinostat. Control experiments on the ground under hyper‐gravity on a low‐speed centrifuge microscope and on a vibration test facility proved that the observed effects were caused exclusively by the reduction of

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04937.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The nuclear apparatus ofH. vermiculareconsists of a single moniliform macronucleus and about 25 micronuclei. the micronuclei are about 3 μm in diameter and characterized by a meshwork of thick condensed chromatin. Mitosis is intranuclear and acentric as in all other ciliates. In metaphase, interpolar and chromosomal microtubules are abundant and the length of the micronuclei increases to about 5 μm. In late anaphase, interzonal microtubules become prominent and the spindle elongates to about 50 μ. In meta‐ and anaphase, the microtubules of the spindle are attached to the polar vesicles, and in anaphase, chromosomes become attached to it. In contrast to most other eukaryotes, micronuclear mitosis is not strictly bound to cell division inH. vermiculare.While most of the micronuclei divide prior to cytokinesis, others retain their interphasic shape or degenerate. In addition, some micronuclei divide in the interdivision period, i.e. between two successive divisions of the cell and macronucleus. Mating cells ofH. vermicularebecome joined to each other in the cilia‐free region covering the cytostome. In the course of conjugation, the cell membranes and the underlying oral filamentous sheaths of both cells fuse, thus uniting the endoplasm of both cells in the mouth region. Synaptonemal complexes in the meiotic chromosomes are more distinct inH. vermicularethan in most other dilates. the micrographs presented here depict dearly the central filament, transverse elements, and other substru

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04938.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The replication band is a large, migrating, macronuclear domain that is the site of DNA synthesis in hypotrichous ciliated protozoa. A number of agents that produce inactivation of this structure and its replicational activity are described here. These agents include heat shock, aphidicolin, cell crowding, various cAMP phosphodiesterase inhibitors and a calmodulin inhibitor. With the exception of aphidicolin, which has a direct inhibitory effect upon DNA polymerases, the mechanisms of inactivation are presently unknown. the inactivating properties of cAMP phosphodiesterase inhibitors suggest that intracellular cAMP levels may influence replication band structure and function.

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04939.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.This study describes the ultrastructure of the somatic cortex ofProrodon aklitolophon and Prorodon teres.the meridionally arranged somatic kineties of both species can be separated into two parts: a short anterior part, which consists of a few somatic dikinetids (in which both kinetosomes are ciliated), and a longer posterior consisting of monokinetids. the somatic monokinetids are associated with a convergent postciliary microtubular ribbon, a transverse microtubular ribbon flatly inserted in front of the kinetosome, a short and steeply extending kinetodesmal fibre attached to kinetosomal triplet 5 and 7, and a desmose anterior to triplet 3. From this desmose, two to five prekinetosomal microtubules originate and extend anteriorly. the posterior kinetosome of the somatic dikinetids is associated with the same microfibrillar and microtubular structures as the somatic monokinetid, except that no prekinetosomal microtubules originate from the desmose. the anterior kinetosome has a single postciliary microtubule and a tangentially oriented transverse microtubular ribbon. the permanent collecting canals of the unique contractile vacuole system extend parallel and adjacent to the somatic kinetics ofProrodon. the collecting canals are supported by the prekinetosomal microtubules. A similarly organized contractile vacuole system is not yet known from any other ciliate group. One of the most surprising results of this investigation was finding a significant similarity between the somatic dikinetid pattern ofProrodonand the colpodid dikinetid pattern. A hypothesis is presented to illustrate the evolution of the somatic kinetid patterns in colpodid and prostomatid ciliates.

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04940.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The ultrastructure of the oral region and the ultrastructural architecture of the basket ofProrodon aklitolophonandProrodon teresare described. the oral region ofProrodonconsists of: 1) A circumoral kinety at the anterior pole of the cell surrounding the typically slit‐shaped cytostomial funnel. This kinety is composed of inversely oriented dikinetids in which both kinetosomes are ciliated and are associated with a very short postciliary microtubular ribbon and a few transverse microtubules; 2) Three brush rows aligned in parallel and extended meridionally in the anterior part of the cell. the individual brush rows consist of dikinetids, but in contrast to the dikinetids around the cytopharynx they are not inverted and only the anterior kinetosomes bear specialized short brush cilia and are associated with a divergent‐tangential transverse microtubular ribbon. the posterior kinetosome is non‐ciliated and bears a prominent convergent postciliary microtubular ribbon. Schematized dikinetid patterns of both oral regions ofProrodonare provided. In addition, a three‐dimensional reconstruction of the basket of the genusProrodonbased on serial thin sections is presented. A phylogenetic tree, mainly based on stomatogenic data, is given to show the phylogenetic relationships of some prostomatid genera as well as the hypothesized sistergroup relationship of colpodid and prostomatid c

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04941.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The morphological characteristics of two new species ofIsosporaobserved in Emberiza cirlus (Cirl Bunting) from Italy are reported. the oocysts ofIsospora normanlevinein. sp. are spherical or sub‐spherical, with a smooth double‐layered wall, and measure 24.2 times 23.7 (21.0‐26.5 times 21.5‐25.5) μm; each oocyst contains 2 to 10 polar granules. No micropyle or residuum was observed. the piriform sporocysts measure 19.4 times 11.2 (17.0‐21.0 times 10.0‐12.5) μm and contain a dispersed residuum. the Stieda body is flat; the substiedal body, with scattered clear and dark granules, may be either symmetrical or asymmetrical. the oocysts ofI. coluzziin. sp. are asymmetrical and rounded shape and measure 28.6 times 24.2 (25.0‐31.5 times 21.5‐26.0) μm. the oocyst has a double‐layered wall and 2 to 3 polar granules. Neither micropyle nor residuum is present. the sub‐ellipsoidal sporocyst, measuring 18.2 times 10.0(16.5‐20.0 times 9.0‐11.0) μm, has a dispersed sporocyst residuum. the St

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04942.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.We recently reported the isolation of a leptomyxid ameba from the brain of a mandrill baboon that died of meningo‐encephalitis. Based on light and electron microscopic studies, animal pathogenicity tests, and immunofluorescence patterns, we conclude that our isolate differs fundamentally from the other two amebas (Leptomyxa and Gephyramoeba) included in the Order Leptomyxida. We therefore created a new genus,Balamuthia, to accommodate our isolate and described it asBalamuthia mandrillaristo reflect the origin of the type species. Briefly,B. mandrillarisis a pathogenic ameba that causes amebic encephalitis in humans and animals. It has trophic and cyst stages in its life cycle, and is uninucleate with a large vesicular nucleus and a central nucleolus. Mature cysts have a tripartite wall consisting of an outer loose ectocyst, an inner endocyst and a middle mesocyst. UnlikeAcanthamoeba and Naegleria, the other two amebas that cause amebic encephalitis in humans,Balamuthiawill not grow on agar plates seeded with enteric bacteria. However,Balamuthiagrows on a variety of mammalian cell cultures and kills mice following intranasal or intraperitoneal inoculation. Based on immunofluorescence testing, 35 cases of amebic encephalitis in humans and three in other animals have been identified worldwide as being caused byBalamuthi

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04943.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY