Is the membrane voltage amplifier of drone photoreceptors useful at physiological light intensities?
✍ Scribed by A. M. Vallet; J. A. Coles
- Publisher
- Springer
- Year
- 1993
- Tongue
- English
- Weight
- 606 KB
- Volume
- 173
- Category
- Article
- ISSN
- 0340-7594
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✦ Synopsis
Free-flying drones (Apis mellifera) were attracted by pheromone to an elevated observation site where they looked for small distant objects, a visual task similar to nuptial pursuit. The brightness of the sky against which drones performed this task was measured as the radiance over a range of wavelengths covering the absorbance spectra of the principal drone rhodopsin and its metarhodopsin. This brightness varied relatively little, by just over one log unit. In laboratory experiments on the intact drone, the amplitude of photoreceptor responses to small decrements in intensity showed a marked maximum when the background intensity depolarized the cells to about -35 mV. The radiance of this optimal background was only 0.2 log units greater than the sky radiance at which most drones were seen. It is argued that because of probable systematic errors the true difference may be less. It is known that in superfused retinal slices voltage-dependent sodium channels amplify small signals under these stimulus conditions. We therefore conclude that this amplification is useful for the major visual activity of the drone.