Filter-Mediated Color Vision with One Visual Pigment

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Abstract
The compound eye of the grasshopper Phlaeoba has alternating bands that appear clear or brown. Electroretinograms recorded from the individual bands have different action spectra: The spectrum of the clear band peaks at 525 nanometers and that of the brown band at 545 nanometers. Spectrally selective whole-eye adaptation with light of either long or short wavelength yields identical action spectra. This evidence suggests that this eye has only one visual pigment, whose spectrum is altered in the brown bands by a screening pigment. In behavioral tests of spontaneous choices between stimuli that appear green to the normal human and those that appear red, the green stimuli are preferred even when the relative intensity is varied by 0.9 log units around the equal-brightness level (determined by the electroretinogram). When some red light is mixed with the green light, the preference for the mixture is less than for the green light alone, even though the mixture is more intense. True color vision therefore seems to exist. Painting the bands shows that behavioral color vision requires the presence of both types. These data suggest that Phlaeoba has true color vision mediated by one visual pigment and suitable optical filters.