The thesis describes a study of the responses to light and temperature of the common blow fly <I>Calliphora vicina</I> Robineau-Desvoidy (Diptera: Cyclorrhapha: Calliphoridae). <I>C. vicina</I> shows a long-day photoperiodic response; long photoperiods lead to the production of developing offspring, short ones cause the flies to produce diapausing offspring. It also has an endogenous circadian rhythm that can be entrained to an external <I>Zeitgeber</I>, such as a light:dark cycle. The first part of the thesis examines the responses of strains of <I>C. vicina</I> from Finland (65<SUP>o</SUP>N), England (51<SUP>o</SUP>N) and Italy (44<SUP>o</SUP>N) to identical photoperiods and temperatures. Critical daylength (the photoperiod at which the response switched from diapause to development) and diapause duration were longer in the 65<SUP>o</SUP>N strain than in the two from further south. The 65<SUP>o</SUP>N strain's photoperiodic response was relatively insensitive to temperature. In contrast, the strain from 51<SUP>o</SUP>N was temperature-sensitive; raising the temperature decreased the amount of diapause at all photoperiods. Diapause incidence and duration in all strains were influenced by environmental factors but the parameters within which these could act were set by the genetic background of the fly. The pattern of increasing diapause incidence and duration with origin at higher latitudes probably reflects a history of differential selection. Crosses between the English and Finnish strains revealed that diapause incidence was induced solely by the adult female. Both parents contributed to diapause duration. Crosses between the Fl flies and backcrosses to the parental lines suggested that hybrid females were biased in their perception of a fixed photoperiod towards their maternal line. The second part of the thesis discusses various aspects of the response to light stimuli of flies fed carotenoid deficient or depleted diets. The response of the visual system was examined directly; that of extraretinal photoreceptors was measured indirectly via behavioural observations. The locomotor activity cycle of a majority of flies reared on a carotenoid-free artificial diet was not entrainable to a light:dark (LD) cycle. Flies reared on carotenoid-deficient heart did entrain to a LD cycle but other aspects of their response suggested reduced efficiency of the extraretinal photoreceptors compared with flies reared on carotenoid-rich liver.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:657654 |
| Date | January 1997 |
| Creators | McWatters, Harriet Goodchild |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15366 |
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