ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05577.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.Behavioral responses to light at different oxygen tensions were studied in the ciliateLoxodes striatus.In the absence of O2it does not react to light. In the presence of O2it reacts to light as if the pO2had been further increased, with the induction of positive geotaxis, a transient phobic response, and finally with a permanent kinetic response (increased swimming velocity and a decreased rate of tumbling). Cells treated with cyanide behave as cells in an anoxic environment and do not react to light. It is concluded that the light response is due to the photochemical production of oxygen radicals and that the sensory receptors for O2and for light are identical. The three types of behavioral response (geotaxis, transient, and kinetic responses) are discussed in terms of their adaptive significance for the orientation ofLoxodesin the natural environment.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05578.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.This study compared the response of protozoan communities colonizing artificial substrates to complex effluents in laboratory microecosystems and validated laboratory predictions using similar sampling methods in the field. Sampling stations were established on a small stream receiving heavy metal and sewage treatment plant effluents. Water from each station was used as a test medium to test the colonization of polyurethane foam artificial substrates in laboratory microecosystems. The heterotrophic index (HI), the ratio of total community biomass to chlorophyll biomass, was also measured. Field colonization trials and HI determinations were carried out at each sampling station. There was a strong negative relationship between the number of species colonizing artificial substrates and the total metal concentration of the water at each station; protozoan colonization was severely depressed at the highest metal concentrations (>400 μg/liter) and recovered at downstream stations where dilution had taken place. The HI differentiated stations receiving high heavy metal concentrations in the field from those recovering from heavy metal influences. Effect concentrations based on laboratory experiments predicted that the concentration of total heavy metal that would produce a 5% decrease in species number (EC5) was 18 μg/liter, approximately the background concentration found in the stream studied. These experiments demonstrated that laboratory microecosystems or microcosms can be used to predict effects in the field accuratel

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05579.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Book reviewed in this article:Beaver, P. C.&Jung, R. C. (with contributions by A. D'Alessandro‐Bacigalupo, J. H. Esslinger, S. P. Katz, M. D. Little, E. A. Malek, T. C. Orihel, and R. G. Yaeger

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05580.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.The purpose of this research was to examine the roles of physico‐chemical parameters in structuring protist communities that colonize artificial substrates. Polyurethane foam (PF) substrates were placed in five lentic systems in northern lower Michigan during summer 1983. These lentic habitats represented a range of trophic states and included three lakes, a bog, and a marsh. Triplicate PF substrates were sampled after 1, 3, 7, 14, 21, and 42 days of exposure. During this study, 90 living protist samples were examined for the number and kinds of species. Water samples were analyzed for pH, conductivity, alkalinity, chloride, silica, temperature, dissolved oxygen, ammonia, and total and ortho‐phosphate concurrent with artificial substrate collections. A total of 546 protist species was recorded. Only seven species were found in over 50% of the samples and 121 species were found in only one sample. The 96 most common species were examined in relation to environmental parameters using several multivariate statistical procedures. Factor analysis (principal components with varimax rotation) performed on the total environmental data set showed that three composite factors explained 85% of the variability of the data set. A reciprocal averaging ordination (RAO) was used to reduce species presence/absence data and to separate samples graphically by their species composition. Significant correlations, with RAO‐generated axes from all five systems, were found for pH, oxygen, and a nutrient factor to axis 1. Factor analysis on the physico‐chemical parameters of the three lakes showed that three factors explained 71% of the environmental data set variability. The RAO‐generated axis (axis 1) was correlated with silica, ortho‐phosphate, and Factor 2, which was primarily comprised of loadings from ortho‐phosphate. These techniques support the hypothesis that a limited number of environmental parameters strongly affect protist communit

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05581.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.Loxodesreached peak abundance close to the oxic‐anoxic boundary (O25% atm) in two lakes, in test tube cultures, and in glass chambers with horizontal O2gradients. Vertical profiles of CO2, pH, sulfide, and Fe2+in a lake were not closely related toLoxodesabundance. In a laboratory experiment,Loxodesfollowed a retreating source of O2and was repelled by a high pO2. This behavior was sustained when cells simultaneously swam up or down gradients of both CO2and pH. Aggregation of cells was abolished by KCN (10‐4‐10‐6M). Sodium azide (10‐1‐10‐4M) had no effect and 2,4‐DNP sharpened the aggregation. Rotenone, Antimycin A, and HOQNO had no obvious effect. Cytochrome oxidase is probably the oxygen receptor.Loxodes striatuscontained low activities of superoxide dismutase and catalase. Extracellular production of superoxide (O‐2) and hydrogen peroxide (H2O2) were probably not responsible for the exclusion ofLoxodesfrom water with a high pO2. Continuous exposure ofLoxodesto oxygen at normal atmospheric pressure at 10°C led to 50% mortality in 10 days. Cells left free to swim in an oxygen gradient doubled their number in the same period. Light exacerbated the toxic effects of O2. Behavioral responses to the dissolved oxygen tension probably controlled the spatial dist

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05582.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.The pellicular ultrastructure ofEuglena ehrenbergiiandEuglena oxyurisis examined for differences that might account for their very different motile activity. Their general ultrastructure is closely similar, but the continuity between adjacent pellicular strips found inE. oxyuriswould severely restrict strip sliding and contribute to this species’very limited cell‐shape changes. The strips ofE. ehrenbergiihave plate‐like projections, whose constant orientation is consistent with strips sliding without deforming obliquely on cell rounding. Some variations and constant features in pellicular ultrastructure are noted and discussed in regard to the sliding strip mechanism for euglenoid shape ch

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05583.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.After formation, food vacuoles in the microstomal cell type ofTetrahymena voraxlabeled with either India ink or cationized ferritin (CF) undergo three morphological stages during processing: an initial condensation with a size decrease, the appearance of a clear halo around the condensed marker that apparently results from expansion of the vacuole, and the disappearance of the halo region. These stages correspond generally to three of the four stages described previously forTetrahymena.Fusion of older vacuoles prior to egestion may represent a fourth stage in vacuole processing. The developing vacuole has small coated regions of the membrane; two populations of vesicles, small coated vesicles and larger vesicles with electron‐dense cores, are adjacent to it. During the initial condensation, tubular invaginations with CF project from the vacuole. After the disappearance of the halo, much of the vacuolar surface appears to be multilayered with extensive folds containing CF. Labeled flattened or curved disks and closed rings occur in the cytoplasm often adjacent to labeled vacuoles and in the vicinity of the cytoproct. The appearance of labeled disks and rings is identical to both labeled and unlabeled vesicles adjacent to the cytopharynx, adding additional support to the hypothesis that, likeParamecium, vesicles retrieved from food vacuoles during processing as well as after fusion with the cytoproct may be reused for vacuole formatio

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05584.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACT.The fine structure of cells and isolated pellicular sheets ofAstasia longais examined in relation to the sliding between neighboring pellicular strips believed to accompany euglenoid movement. Sonication breaks the repeating structure of the pellicle in the groove region where tannic acid fixation resolves separate but overlapping pellicular strips. All microtubules (including the two lying between the overlapping strips) remain with the inner strip. We therefore suggest that this fracture plane defines the boundary where sliding occurs between adjacent pellicular units. Consistent with this, traversing filaments running from groove to groove to connect the pellicular strips of adjacent units are displaced from transverse to oblique when elongated cells round up. In contrast, no changes suggestive of distortion within each unit are detected in the particle arrays of the ridge plasma membrane that overlies a single unit. The results are discussed in relation to previous ultrastructural studies, the site at which the force to cause sliding is generated, and the role of the traversing filaments.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05585.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Book reviewed in this article:Poinar, G. O., Jr.&Thomas, G. M. 1984.Laboratory Guide to Insect Pathogens and Parasites.James, D. M.&Gilles, H. M. 1985.Human Antiparasitic Drugs: Pharmacology and Usage.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1986.tb05586.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY