Blue-green opponency and trichromatic vision in the greenhouse whitefly (Trialeurodes vaporariorum)

Abstract

Visual orientation in the greenhouse whitefly (Trialeurodes vaporariorum Westwood, Hemiptera: Aleyrodidae) is the result of wavelength-specific behaviours. Green-yellow elicits settling behaviour while ultraviolet (UV) radiation initiates migratory behaviour. Electroretinograms of the photoreceptors spectral efficiency showed peaks in the green and the UV range and whitefly vision was said to be dichromatic.\n\nIn order to study the visual behaviour of T. vaporariorum, nineteen narrow-bandwidth LEDs covering the UV-A and visible range were used in combination with light scattering acrylic glass screens in a small-scale choice arena under greenhouse conditions. Multiple-choice and dual-choice assays were performed, resulting in LED-based behavioural action spectra of settling (green) and migratory behaviour (UV). A potential inhibitory blue-green chromatic mechanism was studied by combining yellow with different blueish LEDs. Intensity dependencies were illustrated by changing LED intensities.\n\nRegarding the settling response, highest attraction was achieved by a green LED with a centroid wavelength of 550 nm, while a blue LED with 469 nm proved to be most inhibitory. Behaviour was distinctly intensity dependent. Migratory behaviour was elicited the most by the UV LED with the shortest available wavelength of 373 nm. The results clearly prove the presence of a green and a yet undescribed blue sensitive photoreceptor and a blue-green opponent mechanism. Furthermore, empirical colour choice models were built and receptor peaks were estimated around 510 - 520 nm (green), 480 - 490 nm (blue) and 340 - 370 nm (UV). Consequently, Trialeurodes vaporariorum possesses a trichromatic receptor setup.\n\nSummary statementLED based choice experiments and empirical colour choice models reveal a yet undescribed blue sensitive photoreceptor and an inhibitory interaction with a green sensitive receptor.