The Experts below are selected from a list of 12 Experts worldwide ranked by ideXlab platform
Robert A Andersen - One of the best experts on this subject based on the ideXlab platform.
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38 the sysytematics of ochromonas chrysophyceae
Journal of Phycology, 2003Co-Authors: S M Edgar, Robert A AndersenAbstract:Ochromonas sensu lato is the largest genus in the Chrysophyceae, containing over 100 names. Ochromonas species are biflagellate, naked, plastid-bearing single cells, distinguished from loricate, scaled, colonial and colorless genera. Most, if not all, species of Ochromonas are mixotrophic, i.e., they photosynthesize but they also engulf bacteria and other small prey. Preliminary evidence from SSU rRNA sequences show that Ochromonas is a polyphyletic genus. Ochromonas tuberculata is the most distinct from all other Ochromonas species. The other Ochromonas species (examined thus far) are scattered in three clades. For example, O. danica and O. sphaerocystis are sister to Poterioochromonas stipitata and P. malhamensis. Four additional species (identified by light microscopy as O. elegans Doflein, O. globosa Skuja, O. ovalis Dolfein, O. sociabilis Pringheim) have SSU rRNA sequences identical to P. malhamensis. Of these, only O. sociabilis has been transferred to Poterioochromonas. Thus, at least some species may be synonymous with others. Two clades of marine species are also known, one containing coastal species and the other containing open ocean species. A number of genera (some also polyphyletic) are interspersed amongst the Ochromonas species (e.g., Chrysolepidomonas, Chrysonephele, Chrysoxys, Cyclonexis, Dinobryon, Epipyxis, Uroglena, Uroglenopsis). The goal of this research (just beginning) is to establish a monophyletic Ochromonas, probably by assigning some species to other genera (existing or new). One major problem is that the type species, O. triangulata Vysotskii, hasn't been observed in over 100 years, and it is unclear which of several clades of Ochromonas contains the type. Results will be discussed.
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microtubules of the flagellar apparatus are active during prey capture in the chrysophycean alga Epipyxis pulchra
Protoplasma, 1992Co-Authors: Robert A Andersen, Richard WetherbeeAbstract:The flagellar apparatus ofEpipyxis pulchra (Chrysophyceae) and its role in phagotrophy is described. Prior to feeding, the cell elongates forming a basal stalk, and the flagellar apparatus moves away from the contractile vacuole/nucleus complex. In feeding cells the flagellar apparatus consists of a striated rhizoplast, cytoplasmic microtubules nucleated from the short flagellum basal body, three microtubular roots (R1, R3 with tubulesa-f, R4) and cytoplasmic microtubules nucleated from R1 and R3 roots. The microtubules of the R3 root split forming a small and a large loop under the short flagellum; thea microtubule forms the inner, smaller loop and thef microtubule forms the outer loop. After looping under the short flagellum, thea andf microtubules join and extend deep into the cell along a complex layered structure involving microtubules, the rhizoplast and a mitochondrion. When a food particle is captured between the flagella, the cell forms a feeding cup to engulf the particle. The rim of the developing cup forms as the distal end of thef microtubule slides up the complex layered structure, increasing the size of its loop under the short flagellum. Vesicles fuse between the loops of thea andf microtubules, increasing the surface area and depth of the cup. When the cup is fully formed, the food particle is moved into the cup. Thef tubule returns to its normal position, closing the cup and forming a food vacuole.
Richard Wetherbee - One of the best experts on this subject based on the ideXlab platform.
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microtubules of the flagellar apparatus are active during prey capture in the chrysophycean alga Epipyxis pulchra
Protoplasma, 1992Co-Authors: Robert A Andersen, Richard WetherbeeAbstract:The flagellar apparatus ofEpipyxis pulchra (Chrysophyceae) and its role in phagotrophy is described. Prior to feeding, the cell elongates forming a basal stalk, and the flagellar apparatus moves away from the contractile vacuole/nucleus complex. In feeding cells the flagellar apparatus consists of a striated rhizoplast, cytoplasmic microtubules nucleated from the short flagellum basal body, three microtubular roots (R1, R3 with tubulesa-f, R4) and cytoplasmic microtubules nucleated from R1 and R3 roots. The microtubules of the R3 root split forming a small and a large loop under the short flagellum; thea microtubule forms the inner, smaller loop and thef microtubule forms the outer loop. After looping under the short flagellum, thea andf microtubules join and extend deep into the cell along a complex layered structure involving microtubules, the rhizoplast and a mitochondrion. When a food particle is captured between the flagella, the cell forms a feeding cup to engulf the particle. The rim of the developing cup forms as the distal end of thef microtubule slides up the complex layered structure, increasing the size of its loop under the short flagellum. Vesicles fuse between the loops of thea andf microtubules, increasing the surface area and depth of the cup. When the cup is fully formed, the food particle is moved into the cup. Thef tubule returns to its normal position, closing the cup and forming a food vacuole.
Maria Susana Vigna - One of the best experts on this subject based on the ideXlab platform.
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chrysophyceae y synurophyceae de tierra del fuego argentina
Monografías del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", 2002Co-Authors: Jorgen Kristiansen, Maria Susana VignaAbstract:Chrysophyceae and Synurophyceae of Tierra del Fuego, Argentina. This monograph deals with the study of the Chrysophyceae and Synurophyceae of Tierra del Fuego, Argentina. One hundred and one samples are studied. Twenty-one taxa of Chrysophyceae and thirty-four taxa of Synurophyceae are described, among them forty-two taxa are studied by means of transmission and scanning electron microscopy. Synura spinosa has the widest distribution in the studied area. Chrysopyxis inaequalis, C. iwanoffi, Lagynium delicatulum, L. janei, Chrysococcus rufescens, Ch. triporus, Epipyxis utriculus var. acuta, Spiniferomonas abei, Synura petersenii f. glabra and Mallomonas pillula f. valdiviana, are recorded for the first time for Argentina. The biogeographic distribution of the species is analized. Descriptions of all the taxa, keys to genera, sections and species, illustrations, and notes on the habitat for each species are presented.
Jorgen Kristiansen - One of the best experts on this subject based on the ideXlab platform.
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chrysophyceae y synurophyceae de tierra del fuego argentina
Monografías del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", 2002Co-Authors: Jorgen Kristiansen, Maria Susana VignaAbstract:Chrysophyceae and Synurophyceae of Tierra del Fuego, Argentina. This monograph deals with the study of the Chrysophyceae and Synurophyceae of Tierra del Fuego, Argentina. One hundred and one samples are studied. Twenty-one taxa of Chrysophyceae and thirty-four taxa of Synurophyceae are described, among them forty-two taxa are studied by means of transmission and scanning electron microscopy. Synura spinosa has the widest distribution in the studied area. Chrysopyxis inaequalis, C. iwanoffi, Lagynium delicatulum, L. janei, Chrysococcus rufescens, Ch. triporus, Epipyxis utriculus var. acuta, Spiniferomonas abei, Synura petersenii f. glabra and Mallomonas pillula f. valdiviana, are recorded for the first time for Argentina. The biogeographic distribution of the species is analized. Descriptions of all the taxa, keys to genera, sections and species, illustrations, and notes on the habitat for each species are presented.
Marina Carstens - One of the best experts on this subject based on the ideXlab platform.
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a preliminary study of ne greenland shallow meltwater ponds with particular emphasis on loricate and scale covered forms choanoflagellida chrysophyceae sensu lato synurophyceae heliozoea including the descriptions of Epipyxis thamnoides spnovand pseu
Archiv für Protistenkunde, 1996Co-Authors: Johanna Ikavalko, Helge Abildhauge Thomsen, Marina CarstensAbstract:Summary: The biodiversity of five shallow freshwater and slightly brackish ponds (North East Greenland; 79-81 ° N) has been studied with particular emphasis on taxonomical and ecological aspects of loricate and scale-covered forms, i.echoanoflagellates, chrysophytes and heliozoansThe material was collected in July 1993 as part of the IAAP Northeast Water (NEW) Polynya programme and represents the northernmost freshwater and brackish localities analyzed using electron microscopical techniquesMorphometric data and physical, chemical and biological parameters (pH, temperature, salinity, nutrients, chlorophyll-a) are provided for all ponds sampledThe light- and electron microscopical examination of samples revealed 2 choanoflagellates, 14 chrysophytes and 7 heliozoan taxaSeven species are recorded from Greenland for the first time and two species are considered new to science, viz Epipyxis thamnoides and Pseudokephyrion poculiforme A crucial difference was observed on the one hand between the single land pond (location 33) characterized by high diversity and high biomass, and on the other the glacier and the ice floe melt ponds characterized by low diversity and low biomassBiogeographically the community sampled displays significant similarities with localities previously investigated within the Greenland and northern Canadian region.