I examine whether it is possible for the temporal resolution and reliability of a photoreceptor to vary across the eye. This possibility has not been addressed before in any animal and yet it is important for our understanding of how visual systems may be designed to register patterns of optic flow or to track moving targets. In the male blowfly, <I>Calliphora vicina, </I>I show that both spatial and temporal acuity are higher at the front of the eye and fall off with retinal eccentricity. The particular pattern of tuning observed emphasises the importance of tracking to the male fly, a behaviour commonly observed in flies prior to mating. To investigate this possibility further, in Chapter 3 I compare the responses of male and female photoreceptors to simulated target stimuli. For this purpose I use the housefly, <I>Musca domestica</I>, a species whose anatomical and behavioural sex-differences are well documented. The male photoreceptor responds much more powerfully to small moving targets than the female and response amplitude greatly exceeds that predicted from conventional models of photoreceptors dynamics. In particular, the male photoreceptor boosts the signals generated by targets moving within the behavioural regime of distances and speeds. These results allow the limits of male pursuit vision to be determined and demonstrate the impact of behaviour on retinal function. Adaptation of photoreceptor sensitivity and temporal resolution to ambient illumination is a well-known phenomenon. This process is usually considered to be complete within seconds. However, I show in <I>M. domestica</I> that significant improvements in temporal resolution and reliability can occur over a much longer period. These improvements are derived from a more consistent registration of the timing of photon absorption events and appear to be associated with a reduction in rhabdomeral surface area.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597151 |
| Date | January 2002 |
| Creators | Burton, B. G. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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