The kissing bug, Rhodnius prolixus, likely has a single functional photoreceptor in their eyes

Kissing bugs are blood-sucking hemipteran insects, serving as the vector of Chagas disease in the Americas. Around 8 million people are infected with Chagas disease yearly, and 20-30% of infected individuals develop life-threatening conditions. Vision is one of the vital sensory aspects for host searching and other roles in triatomine life. The role of kissing bug vision in their nocturnal lifestyle, including host-seeking, resting time, and emergence from harborage, has yet to be fully examined. Opsins are the main photoreceptor molecules in animals and are essential for phototransduction. Therefore, an in-depth examination of the visual system of kissing bugs is required. Transcriptomics, phylogenetic, and extracellular electroretinogram (ERG) analyses were used to identify and characterize the opsins and visual processes in the compound eyes for Rhodnous prolixus. RNA-seq of the eyes and phylogenetic analysis confirmed three visual opsin genes, one is highly expressed in eyes and is likely a blue-green sensitive. Electroretinogram analyses of adult R. prolixus to measure the spectral response to monochromatic light stimuli found the highest response at the blue (480 nm) region. Photoreceptor bleaching experiments with UV (365nm), blue (460nm), and orange (605nm) LED lights found that bleaching with specific wavelengths attenuated the entire response, suggesting a single functional opsin. Our result suggests that one blue-green opsin is responsible for the response to light stimuli by kissing bugs. Knowing the spectral classes of photoreceptors in kissing bugs is critical to understanding their vision and could provide novel targets to alter the behavior of these pests.