Chemoreception of an oviposition deterrent associated with eggs in pieris brassicae
1978
Behan, Mary | SCHOONHOVEN, L.M.
Electro-antennograms (EAG) in Pieris brassicae butterflies showed graded responses to the odour of intact conspecific eggs, and also to leaf and flower volatiles Contributing to this summated potential are at least two types of sensilla on each segment of the antenna, although the terminal 6-8 segments do not respond proportionately. Analysis of the activity profiles of single olfactory cells to these compounds shows a typical generalist spectrum, with 0-3 cells per sensillum responding to the stimulus by an increase or decrease in spike frequency. The pheromone associated with eggs and deterring other females from ovipositing is not present in ovaries, but is produced in the accessory glands. It is water-soluble, has a low volatility and causes an increase in spike frequency in tarsal contact chemoreceptors. Behavioural evidence for the presence of a three-tier discrimination (visual detection of eggs or larvae, olfactory detection of aversion pheromone during fluttering over the leaves: contact discrimination by tarsae after landing (Rothschild & Schoonhoven, 1977)) is supported by electrophysiological results, which indicate the involvement of olfactory and contact chemoreceptors in recognising the presence of eggs.
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