ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary InDrosophila polarization sensitivity as revealed in optomotor experiments is mediated by retinula cells R1–6. In the optomotor turning response of the walking fly the response amplitude is a sinusoidal function of E-vector orientation of the stimulus light. For the effect to occur the area of the visual field in which moving vertical stripes are presented must be embedded in an illuminated surround which covers a large part of the visual field. The phase and amplitude of this sinus function do not reflect directly the polarization sensitivity of the photoreceptors mediating it since a) the amplitude is much larger than could be expected from the measured properties of fly retinula cells, b) the effect can be elicited in parts of the visual field viewed by photoreceptors of which half are oriented in mirror symmetry to the other half (equator, frontal area), c) presentation of the stimulus to either eye (at the same height) does not lead to a phase shift in the sinus functions. (A phase shift of 90 ° would be expected in our experiments if the response reflected the fly's bilateral symmetry.) The data suggest that the fly has an “inner” representation of E-vector orientation. In a closed loop situation in which the fly is illuminated from above by linearly polarized light and is allowed to turn the orientation of the E-vector plane relative to its body axis by its yaw torque it can maintain its optomotor balance (i.e. it can fly straight). Often flies keep their longitudinal body axis roughly parallel or perpendicular to the E-vector plane during the whole experiment (4 min). Flies perform discrete 360 °-loops although the rotating polarizing filter has a 180 ° period. Viewed in the context of the first experiment this observation suggests that the fly, like the bee, evaluates the polarization pattern as a whole and designs its loons accordingly. At least on clear daysDrosophila can make use of the polarization pattern of the free sky in flight orientation. Polarization sensitivity is not restricted to the upper part of the eye: Also with the lower part the fly can use a polarization pattern for course control.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00657080
Permalink
