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Abstract:
Phototaxis and optomotor reactions of the mutantsebony and opm 2 are investigated.
LikeMusca, Drosophila has two complementary visual input systems, one specialized (e. g.) in optimal contrast transfer (high acuity system, HAS, retinula cells 7 and 8) the other in high sensitivity (HSS, retinula cells 1–6).
Inebony the HSS seems to be blocked for phototaxis and optomotor responses (Figs. 1 A, 5). However, even the HAS has a higher threshold intensity than in wild type (Fig. 5). In opm 2 the HSS is disturbed for phototaxis (Fig. 1) but is operating for the optomotor response (Fig. 6). However the HAS seems to be largely suppressed for the optomotor response (Table 2). In the double mutantebony-opm 2 both visual input systems seem to be impaired for movement detection (Fig. 7).
Two other properties of the visual system of opm 2 are described. The visual fields of the sampling stations for movement detection are about twice as large as in wild type (Figs. 2A, B). This can not be explained by a disturbance of the optics. In other mutants of this type the visual field size is slightly different.
In opm 2 the reaction to movement from front to back (progressive) is specificly suppressed, whereas, at least in flight, the reaction to movement from back to front (regressive) is normal (Table 1, Figs. 3, 4). The degree of suppression of the reaction to progressive movement is variable in individual flies and differs for the three mutants of the opm 2-group (Table 1).
In a simple example the use of these mutants for system analysis experiments is demonstrated.
