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  • 1995-1999  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    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
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1998.tb04556.x
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  • 2
    Electronic Resource
    Electronic Resource
    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
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1998.tb05088.x
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  • 3
    Electronic Resource
    Electronic Resource
    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
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1999.tb05124.x
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  • 4
    Electronic Resource
    Electronic Resource
    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
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1999.tb06071.x
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