ISSN:
1432-1351
Keywords:
Anemotaxis
;
Carrion beetles
;
Course control
;
Menotaxis
;
Necrophorus humator
;
Wind-orientation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The wind-orientated walk of carrion beetles Necrophorus humator F. was analysed under closed-loop conditions with a walking compensator and under openloop conditions with a paired tread wheel (Fig. 1). 1. On the walking compensator an animal runs stable courses with a preferred direction relative to an air current (velocity =; 100 cm/s, Fig. 2B-D). A change in the air-current direction causes a corresponding adjustment of the mean walking direction (Fig. 3). Such course adjustment works best for changes in the air-current direction by an absolute value of 90° (Table 2). 2. Under closed-loop conditions the animal shows deviations of less than ± 45° around its preferred direction relative to the wind (Fig. 2B-D). The characteristic curve which describes the animal's angular velocity as a function of the animal's walking direction relative to the air-current stimulus is therefore revealed only in this angular range (Fig. 3, top). 3. Under open-loop conditions, however, complete characteristic curves can be obtained because the animal's walking reaction in response to any given angle of air-current stimulus is measurable on the paired tread wheel (Fig. 4). The characteristic curves are approximately sinusoidal functions. They can either show a shift parallel to the ordinale by a superimposed direction-independent constant angular velocity alone or, at the same time, they can independently exhibit an angular shift along the abscissa (Fig. 5). 4. The walking tracks straighten with increasing air-current velocity (Fig. 6A, insets), i.e. the animal more rapidly compensates deviations from a preferred course. This corresponds to higher amplitudes of the characterisic curve and steeper slopes at the negative zero-crossing point under open- as well as under closed-loop conditions (Fig. 6). 5. Walking in an air-current field can be explained by a model of the course control system using a feedback loop (Fig. 7). This model operates according to a sinusoidal characteristic function on which is superimposed a Gaussian white noise process of angular velocity which is independent of walking direction. The model produces realistic walking tracks in an air-current field (Fig. 8).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00194896
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