, Volume 139, Issue 4, pp 261-266

Electrophysiologically determined spectral efficiencies of the compound eye and median ocellus in the bumblebeeBombus hortorum tarhakimalainen (hymenoptera, insecta)

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  1. Intracellular responses to 30 μs flashes of 11 different spectral lights have been recorded from 75 retinula cells belonging to the eyes of 12 blumblebees.

  2. Three basic types of retinula cells were found: 11 cells possessed a singular significant peak in the UV (353 nm), 10 cells had a clear peak in the blue (430 nm) and a secondary peak in the UV, and 54 cells exhibited greatest sensitivity in the green to light of 549 nm wavelength.

  3. Cells sensitive to green light possessed a secondary peak in the UV which reached 75% of the maximum amplitude at λmax, when the flash quantum content was 2.4 ± 0.06×1010. However, when the light intensity was reduced to 12% of this value, the secondary peak in the UV fell to 50% of the λmax response (obtained with the dimmer light).

  4. By using a method developed by Menzel (1975), it was possible to show that in the bumblebee eye all spectral cell types can occur in the same ommatidial group.

  5. ERG-recordings from the median ocellus resulted in a double-peaked spectral efficiency curve with a maximum at 353 nm and a secondary peak at 519 nm.

  6. The electrophysiologically determined spectral efficiency curves were compared with peaks obtained by optical means (Bernard and Stavenga, 1978). Congruity existed only for spectral response maxima from the UV receptor.

I wish to thank Professor Leo Hirvonen, Head of the Department of Physiology at the University of Oulu, for the assistance and hospitality I have received while carrying out this research in Oulu, Finland, and I am grateful to Dr Matti Järvilehto for allowing me to use his electrophysiological set-up.