Archiv für Protistenkunde最新文献

The typical cercomonad structure (based on original investigations of Heteromita sp., Cercomonas agilis and literature data) is as follows: the amoeboflagellate cell is covered by only a distinct glycocalyx; there are two flagella, extrusomes, microbodies, mitochondria with vesicular cristae, and the nucleus has a sharp end directed towards the basal bodies. Absolute orientation of the flagellar apparatus reveals an anterior basal body directed in a forward or ventral direction, and the posterior basal body is located on the ventral side and is directed to the right. There are 2–4 lateral microtubular rootlets, a layered structure and a nuclear fibrillar rootlet. A dictyosome occupies the dorsal position. The life-cycle of cercomonads includes a plasmodial stage. Comparison of cercomonad morphology and life-cycles with those of myxomycetes (predominantly with zoospores of protostelids) and Hyperamoeba flagellata (a fresh-water protist of uncertain taxonomic position) reveals the homology of structures in the flagellar rootlet system; the same absolute orientation of the flagellar apparatus and dictyosome; and mitochondria with vesicular cristae. Homology of the main stages in the life-cycles of all three groups has been also proposed. The relationship of cercomonads and protostelids has been confirmed by new ultrastructural data, and H. flagellata is considered as a bridge between these two groups. This view contradicts molecular data which usually demonstrates a long distance between cercomonads and myxomycetes.

The taxon Euglenozoa was originally created to include the kinetoplastids and euglenids only. Subsequently, euglenozoan identity and/or affinities have been suggested for Diplonema, Stephanopogon, the Hemimastigophora and several even more poorly understood eukaryotes. The Euglenozoa have only ever been defined by circumscription and/or composition; attributes that change as taxa are added or removed.

This paper seeks to refine and stabilise the concept of the Euglenozoa by redefining it as a clade identified by synapomorphy. It is proposed that the Euglenozoa be identified by the character 'heteromorphic (tubular and parallel) lattice paraxonemal rods’. Applying this definition, the Euglenozoa currently consists of four subgroups; euglenids, kinetoplastids, diplonemids (i. e. Diplonema and Rhynchopus) and Postgaardi. The reasons for the exclusion of Stephanopogon and the Hemimastigophora are also presented.

A 1268-bp DNA fragment representing 25% of the RNA polymerase II largest subunit gene has been used to infer the phylogenetic relationships among four Sauroleishmania species, and their relatedness to the closely related genera Leishmania and Endotrypanum. Comparison of the nucleotide sequences showed that 94% of phylogenetically informative sites occurred at silent codon positions. Distance (neighbor-joining) and weighted parismony analysis of the nucleotide sequence alignment each produced alternate optimal trees which varied in the placement of L. (Viannia) braziliensis and the Sauroleishmania. The cost of branch swapping (number of steps in parsimony analysis) indicated that few steps were required to alternate between these topologies (representing 0.5% of total tree length). In contrast, distance and parsimony analysis of the predicted protein sequence yielded congruent results. The calculated homoplasy, retention and rescaled consistency indices of the protein sequence data indicated that homoplasy was significantly reduced in the protein sequence alignment as compared to the nucleotide sequence alignment. The protein-inferred phylogenies provide strong support for the monophyly of the Sauroleishmania and indicate that these parasites emerged subsequent to the separation of the Leishmania subgenera L. (Leishmania) and L. (Viannia). The close affiliation between Leishmania and Sauroleishmania suggests that the lizard parasites might best be retained in the genus Leishmania.

On the basis of the maximum likelihood (ML) method of protein phylogenetics, we have examined a protozoan phylogeny by using the amino acid sequences of translation elongation factors EF-1α and EF-2. When the results of individual ML analysis were totally evaluated, it was suggested (a) that three mitochondrion-lacking lineages, microsporidians, diplomonads, and trichomonads have diverged from the line leading to higher eukaryotes in the early phase of eukaryotic evolution, (b) that microsporidians are the earliest offshoot of eukaryotes among these three lineages, and (c) that Euglenozoa are not likely to have diverged next to diplomonads as suggested by the small subunit ribosomal RNA (SrRNA) tree, but show a close affinity with higher eukaryotes. Previous results have shown that the amino acid compositions of EF-1α and EF-2 do not differ significantly among species, and hence the present EF phylogenies are expected to give a robust estimation for early divergences of eukaryotes.

The occurrence of species of the Paramecium aurelia complex was studied in material collected in 1995 in Baden-Württemberg, Germany. Also five strains collected previously in Münster (Westphalia) and Stuttgart (Baden-Württemberg) were identified. Identification was carried out by mating the clones with the mating types of the standard strains of known species of the P. aurelia complex. The presence of P. biaurelia, P. triaurelia, P. sexaurelia, and P. novaurelia was revealed. All species were found in Stuttgart or in its neighbourhood (Baden-Württemberg), and two species (P. biaurelia and P. novaurelia) in the material from Münster (Westphalia). In some strains endosymbionts were found, Caedibacter sp. Preer, Preer, Jurand: (1974) in the cytoplasm, and Holospora caryophilaPreer and Preer: (1982) in the macronucleus.

Ice biota studies in the Antarctic region, Weddell Sea, have focused on an examination of single cells and an analysis of community structure of the flagellate assemblage from sea ice and comparisons with planktonic assemblages. Based on extensive light microscopical analysis of 40 samples ranging from open water to “brown-ice” habitats, it became evident through clustering of the data, that the mature choanoflagellate community from ice is significantly different from both the water column community and those encountered in samples derived from newly formed ice (i.e. grease ice, platelet ice, nilas and thin pancakes). The choanoflagellates from sea ice encompasses a range of previously undescribed loricate taxa (Acanthocorbis nana sp. nov., A. weddellensis sp. nov., A. prolongata sp. nov., Apheloecion antarctica sp. nov., A. glacialis sp. nov., A. conicoides sp. nov., Calliacantha frigida sp. nov., C. ankyra sp. nov., Diaphanoeca multiannulata subsp. nov. glacialis, Parvicorbicula corynocostata sp. nov., P. pachycostata sp. nov.). These taxa have been investigated using a combination of light, and electron microscopy. A preliminary investigation of samples from the Arctic (NE Greenland) indicates that the loricate choanoflagellate diversity is significantly lower in Arctic sea ice.

The examination of 75 samples collected in 1986 and 1990 in the central and eastern French Pyrenees revealed a number of new, rare or noteworthy desmid taxa. In the present paper 22 taxa, belonging to the genera Gonatozygon, Closterium, Actinotaenium, Euastrum and Cosmarium are depicted and discussed. Of four taxa name and/or taxonomic status are changed: Actinotaenium kriegeri stat. nov., Cosmarium difficile var. messikommeri comb, nov., Cosmarium horizontale stat. nov. and Cosmarium simplicius var. puerile nom. nov. & stat. nov. Two taxa are newly described: Cosmarium arrense spec. nov. and Cosmarium neouviellense spec. nov.

The relationships of 13 common oxytrichid genera were analysed using cladistic methods (Hennig, PAUP). Twenty-three characters in four groups were selected, viz. the morphology of the oral apparatus (three characters), infraciliature of ventral and dorsal side (ten characters), cortical features (two characters), and ontogenetic particulars (eight characters). All characters and character states are described and discussed using published and original data. Half of the characters originated independently in several genera at least twice, making it very difficult to follow oxytrichid evolution. The autapomorphies of the family Oxytrichidae are 18 characteristically arranged fronto-ventral-transverse cirri and the fragmentation of at least one dorsal kinety. The cladograms show two major branches, termed subfamily Oxytrichinae Jankowski and subfamily Stylonychinae n. subfam. The Oxytrichinae have a unique synapomorphy, viz. the participation of cirrus V/3 in primordia formation. This subfamily contains the genera Cyrtohymena, Gonostomum, Notohymena, Onychodromopsis, Oxythcha, Tachysoma, Urosoma, Urosomoida and, very likely, Australocirrus, Parurosoma and Pseudostrombidium. The Stylonychinae have three synapomorphies, viz. the rigid body, an oral apparatus of more than 40% of body length, and the lack of cortical granules. This subfamily comprises Coniculostomum, Histriculus, Steinia, Sterkiella, Stylonychia and, very likely, Parastylonychia and Pleurotricha. The family Oxytrichidae, its subfamilies, and the genera included are characterized and keyed. An unambiguous terminology is established for oxytrichid hypotrichs, and synonymy and nomenclature of genera are discussed.