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  • 1
    Digitale Medien
    Digitale Medien
    Warm Microgradients Elicit Adaptive Behavior in Isotropically Cooled, Inert Populations of Oxytricha bifaria (Ciliophora, Hypotrichida) (1999)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 46 (1999), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: In order to investigate the physiological potentialities of behaviorally inert Oxytricha bifaria, cooled from 24 to 9° C according to an already standardized protocol, a warm microgradient was created in the experimental chamber and the behavior of ciliates was analyzed both at the level of the passing warm wave front (dynamic microgradient), and, afterwards, when the thermal gradient stabilized (static microgradient). We monitored the general behavior of the experimental populations by means of (i) their centroid, (ii) the ethograms of single oxytrichas, and (iii) calculating the numerical indices and rates of their creeping tracks. It was found that (a) the population moves towards the heating source, (b) the oxytrichas react immediately to the thermal stimulus, (c) creeping forwards (d) at very high velocity (e) along uninterrupted looping tracks (f) according to precise mechanisms of positive/negative orthokinesis, thus orientating towards the environmental optimum. Moreover, (g) the ciliates accumulate in the warmest area, correcting their creeping by means of many specific behavioral patterns (the Side Stepping Reaction) once the gradient is stabilized. At 9° C, despite their inertness, the ciliates are still able to behave adaptively reacting immediately and orientatedly, once a directional factor (the thermal gradient) arises in an isotropic environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1999.tb06071.x
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  • 2
    Digitale Medien
    Digitale Medien
    A Quantitative Approach to Movement, Displacement, and Mobility of Protozoa (1998)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Diffusion theory can completely describe the movement of a ciliate along a track of a certain length (L), travelled in a time (t), and with the extremes lying at a distance D. Three important descriptors of this behavior are: (1) the kinetic index (Ik= L/t), namely the average velocity in μm/s, which expresses the state of the “accelerator” of the ciliate; (2) the geometric index (Ig= D/L) measuring the straightness of the track by a dimensionless number. 0 ≤ Ig≤ 1, which expresses the state of the “steering wheel” and represents a sort of “directional efficiency”; and (3) the displacement rate (Rd= D/t), integrating the first two indices and expressing the combined effect of the “accelerator” and the “steering wheel” of the organism with a unique measure (in μm/s), which defines the average displacement rate or the effectiveness of the track in displacing the organism in space. A weighted estimate of general mobility is given by the mobility rate [Rmo= (R̄d.f)creeping- (R̄d.f)swimming], obtained by multiplying the average Rd of the creeping organisms and the average Rd of the swimming organisms by their relative frequencies of occurrence (f), and adding the two products. Values for experimental populations of Oxytricha bifaria (Ciliata, Hypotrichida) maintained at 24, 19, 14, and 9° C demonstrated both the appropriateness and the usefulness of these indices and rates to describe the tracks a posteriori, and to provide measures to reason about their possible adaptive significance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1998.tb04556.x
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  • 3
    Digitale Medien
    Digitale Medien
    The Effects of Cooling Conditions on the Behavior of Oxytricha bifaria (Ciliophora Hypotrichida) (1998)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The new analytic approach to the behavior of ciliates represented by the ethogram was used to study the locomotion of Oxytricha bifaria at different temperatures, isotropically applied according to a new protocol. It was shown that under these experimental conditions as the temperature dropped in stages from 24°C to 19°C to 14°C to 9°C, the general mobility of experimental populations decreased, as indicated by 1) the decreasing percentage of mobile organisms, 2) their decreasing velocity, 3) their prolonged backward creeping, and 4) the increasing length of their immobilization periods. The ethogram more particularly revealed that decreasing temperatures induced 1) the appearance of rightward arcs (several of them being travelled by specimens sliding on the substrate). 2) the reduction of both the radius and the velocity along the normal leftward arcs (A-) and the segments (S), and 3) the symmetric increase of both the central angle and the duration of the A- and S. These changes were reversibly induced: they disappeared when the temperature returned to 24°C. Moreover. a new behavioral pattern, the prolonged Side Stepping Reaction, was found. Helicoidal swimming, occurring only at 14°C, was analyzed. Among all of the behavioral parameters, nine were shown to change dramatically between 14°C and 9°C, demonstrating that the linear cooling of the populations induced clear non-linear effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1998.tb05088.x
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  • 4
    Digitale Medien
    Digitale Medien
    The Behavior of the Doublet of Oxytricha bifaria (Ciliata, Hypotrichida): A Contribution to the Understanding of This Enigmatic Form (2000)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 47 (2000), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . The tracks of normal organisms of Oxytricha bifaria and of stage IA, IB, II, III, IV and V doublets were studied to test the hypothesis that the doublet might function as a dispersal form. Stage IA, the only stage to swim, swims straight with only rare interruptions; its rate of mobility (Rmo= 443 μ/s) is roughly twice that of singlets (Rmo= 218 μ/s). Stage IA doublets swim in three-dimensional movement which enables them to be carried away by water currents. The other stages seem to represent passage back towards the normal singlet form. The ethological evidence reported here together with other results already published supports the working hypothesis that the doublet of O. bifaria is a dispersal form suggests that the doublet might well represent a special fourth differentiation state of this species in addition to pairs, giants, and cysts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.2000.tb00025.x
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  • 5
    Digitale Medien
    Digitale Medien
    Cold Microgradients Elicit Adaptive Behavior in Isotropically Cooled, Inert Populations of Oxytricha bifaria (Ciliophora, Hypotrichida) (2000)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 47 (2000), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . To complete our investigations on the oriented behavioral response of isotropically cooled, inert populations of Oxytricha bifaria to a warm thermal gradient, their physiological potentialities under cold microgradient conditions arising at 8.5°C were studied. We monitored the behavior of the experimental populations, both at the level of the passing cold wave front, and afterwards when the thermal gradient stabilized, evaluating (i) their distribution in general, (ii) their relative centroids, (iii) the percentage of both backward creeping and immobile ciliates, and (iv) the numerical indices and rates of their creeping tracks. At the arrival of the cold wave front, the oxytrichas react immediately to the thermal stimulus, creep backwards at very high velocity along uninterrupted linear tracks, and thus move away from the cooling source. No specific behavioral response was ever observed in the static microgradient conditions. At 8.5°C, despite their inertness, the ciliates are still able to behave adaptively, reacting immediately and orientatedly, once a directional factor (the cold-repelling thermal gradient) arises in an isotropic environment. This is similar to their behavior in the symmetric warm attracting thermal gradient.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.2000.tb00061.x
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  • 6
    Digitale Medien
    Digitale Medien
    Rheotaxis In Uronychia Setigera (Ciliata, Hypotrichida) (1999)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 46 (1999), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . The behavior of populations of Uronychia setigera (Ciliata, Hypotrichida) exposed to water currents flowing at increasing velocities (300, 400, 500, 900, 1,700 μm/s) was analyzed using two techniques: 1) the ethogram and 2) the numerical indices recently proposed to measure the development in space and time of tracks of ciliates. Beyond a certain threshold value of the water velocity (˜ 300 μm/s), this species shows a definite positive rheotaxis, only if it moves in a more or less direct contact with the substrate. No rheotactic swimming ever occurs. Rheotaxis is a gradual, adaptive behavior: the higher the velocity of the current, the stronger the degree of the rheotactic response, as demonstrated by the increasing significance of the polar distribution of the tracks. Beyond 500 μm/s the water flow is so strong that it affects the locomotion of U. setigera continuously and strongly inducing this species to perform a new behavioral pattern, the Fast Backward Bidimensional Swimming. Under stressing water currents it reacts at first by creeping along straighter trajectories and then with faster locomotion, in such a way that its reaction is to a certain extent proportional to the drag of the currents. the rheotaxis of U. setigera is discussed as an adaptive response.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1999.tb05124.x
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  • 7
    Digitale Medien
    Digitale Medien
    The Interface Between Air and Water: A Perturbation Source Eliciting Adaptive Behaviour in Ciliates (1992)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 39 (1992), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Interference with the water-air interface, both direct (by contact with a flat, rigid surface) and indirect (by inducing a meniscus) caused the ciliated protozoa we investigated to actively collect in the water column or on the substrate directly under the area of altered surface tension. A crowding effect is observed in this “rest area” reaching plateau values within one hour after onset of the experiment. The simple experimental procedures described here induced analogous behaviour in both Paramecium caudatum (a swimmer) and Oxytricha bifaria (a crawler). The ciliates seem in this reaction to be seeking a refuge from vibrations transmitted by the free interface. Our discovery is discussed in its implications for the adaptive biology and ecology of these micro-organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1992.tb04843.x
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  • 8
    Digitale Medien
    Digitale Medien
    Substrates Determine Spatial Distribution of Oxytricha bifaria (Ciliata Hypotrichida) (1989)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 36 (1989), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The extent to which a particular substrate (scratched glass) affects the distribution of a population (Oxytricha bifaria) that settled on it was measured, yielding the following results: (1) the species distinguishes among substrates slightly differing in the quality of their superficial scratches (average dimensions of 2, 2.8, 3.5, 6.5, 17 and 25 μm, respectively); (2) it “chooses” the preferred substrate by adopting specific differential behaviors; and (3) population cell density conditions its overall distribution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1989.tb01098.x
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  • 9
    Digitale Medien
    Digitale Medien
    Ionic Resistance in Strains of the Tetrahymena pyriformis Complex (1981)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 28 (1981), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . Strains of Tetrahymena thermophila were examined in an attempt to establish what role certain ions (Na+, K+, Li+, Ba++, Ca++, Mg++, Mn++, Al+++, Fe+++) play in influencing cell survival time in a culture medium. In short-term experiments (20–30 min), cell survival time in a 1% peptone medium is directly related to the valence of the ion employed. Long-term observations (lasting up to five days) in a 1% peptone medium containing lower ion concentrations revealed that the effects on cell-cycle time are not correlated with the valence state of the ion. Comparisons were made among the ionic resistances of strains of T. thermophila, of T. pyriformis sensu stricto, and of two subspecies of T. pigmentosa. Strains within a species are highly correlated in their patterns of ionic response, while marked differences between species occur. The most distinctive group of strains examined came from one of the subspecies (syngen 6) of T. pigmentosa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1981.tb05319.x
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  • 10
    Digitale Medien
    Digitale Medien
    Mating-Type Dependent Cell Pairing in Oxytricha hymenostoma. III. Chromatin Mixing After Macronuclear Fusion (1980)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 27 (1980), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SYNOPSIS. Mating-type dependent cell pairing in Oxytricha hymenostoma was studied by both light autoradiography and transmission electron microscopy. The process results in the macronuclear bodies of the 2 partners fusing completely with each other 2 by 2. In each fusion the 2 chromatin masses, easily distinguishable from each other for the first 6 h of the pairing, progressively intermingled and underwent a sort of rearrangement so that they eventually acquired a uniform pattern. The possible mechanisms regulating macronuclear fusion and DNA amount in the daughter cells are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1980.tb05398.x
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