Color vision in insects: insights from Drosophila

Abstract

Color vision is an important sensory capability that enhances the detection of contrast in retinal images. Monochromatic animals exclusively detect temporal and spatial changes in luminance, whereas two or more types of photoreceptors and neuronal circuitries for the comparison of their responses enable animals to differentiate spectral information independent of intensity. Much of what we know about the cellular and physiological mechanisms underlying color vision comes from research on vertebrates including primates. In insects, many important discoveries have been made, but direct insights into the physiology and circuit implementation of color vision are still limited. Recent advances in Drosophila systems neuroscience suggest that a complete insect color vision circuitry, from photoreceptors to behavior, including all elements and computations, can be revealed in future. Here, we review fundamental concepts in color vision alongside our current understanding of the neuronal basis of color vision in Drosophila, including side views to selected other insects.

The use of light spectrum blocking films to reduce populations of Drosophila suzukii Matsumura in fruit crops

“…To reveal spectral sensitivity flies chose between a dark stimulus and a set waveband of light (Table 3 , 340 to 660 nm)with perceptible light triggering the animals innate phototactic approach behaviour 18 . D. suzukii females preferentially approached light in the near-UV range (340, 365, 405 nm) in common with D. melonagastor 30 that possess UV-sensitive photoreceptor R7p and R7y and true colour vision with photoreceptor rhodopsins Rh3 and Rh4 31 – 33 .…”

“…Then differential phototaxis experiments 18 were conducted which tested wavelength preference between the discrete wavebands listed above and a 365 nm control (Table 3 ). No significant preference was observed between 365 and 340 nm stimuli but D. suzukii showed a preference for 365 nm when presented in combination with higher wavebands (405 nm-660 nm) (Fig.…”

“…The first group, control was to ensure there was no bias between the arms of the equipment. The second group tested light vs dark (phototaxis 18 ) to ensure that D. suzukii responded to the different wavelengths in the absence of light in the other arm. Finally, the wavelengths were tested against 365 nm for preference to orientate (differential phototaxis 18 ).…”

“…Each ommatidium contains three families of photoreceptors; R1-R6, R7 and R8. All three photoreceptor sets are thought to be involved in both motion detection and colour vision 18 – 20 . Spectral sensitivity for motion shows two peaks, one at c.350 nm and a second at c.470 to 500 nm 21 , 22 .…”

Visual circuits in arthropod brains

“…In contrast to a wealth of studies on motion vision, the neural networks underlying color vision have been studied less well and principles of neural processing and interactions are just beginning to be elucidated. The section on color and polarization vision starts with a comprehensive review of current knowledge on neural mechanisms underlying color vision in Drosophila and other insects (Schnaitmann et al 2020). The authors review the role of color vision in insects and evidence for the emergence of color opponent pathways in the lamina and medulla.…”