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How did jewel beetles’ visual systems evolve?

Jewel beetles are a striking species of insects that can be easily recognized by their metallic sheen and vivid colors. They possess a highly developed visual system that helps them engage in a variety of behaviors, such as finding mates and host plants, and their color vision is different from ours, with special genes allowing them to see ultraviolet (UV), as well as blue and green light. 

To shed more light on the complexity of these insects’ vision, a team of researchers led by the University of Minnesota has recently investigated their evolutionary history and discovered that jewel beetles have duplicated some of the ancestral genes responsible for color perception, allowing them to detect more complicated and diverse color signals.

The experts built on a previous study published in the journal Nature showing that, before the evolution of modern beetles, their ancestors lost the ability to see blue light around 300 million years ago, most likely because they became nocturnal or started living in low-light conditions. Later on, as they diversified, beetles evolved duplicates of the ancestral genes allowing them to detect the UV and green spectrum.

In the current study, the researchers set to find out whether these duplicate genes have evolved, allowing modern beetles to see colors that their ancestors were not able to detect. Since jewel beetles are notoriously difficult to keep and work with in the laboratory, the scientists copied the genes and inserted them into fruit flies, replacing their normal visual genes. Then, by using electrophysiology, they tested the color sensitivity these genes produced in the flies, focusing on genetic changes underlying the shifts in color sensitivity.

The analysis revealed that jewel beetles have evolved additional blue and orange sensitivity by duplicating their UV and green visual genes, enabling complex tetra-chromatic color sensitivity to UV, blue, green, and orange wavelengths (similar to the color sensitivity of various species of colorful birds). When visual genes were modified and retested, the newly evolved genetic changes related to color detection were not found to shift sensitivities.

In future studies, the scientists aim to better understand the molecular bases of beetles’ color sensitivity and – according to lead author Camilla Sharkey, an expert in Ecology, Evolution, and Behavior at Minnesota – “determine if specific types of color vision can be predicted from genes and how color vision is used by insects to better manage pest and pollinator insects, thus improving crop production.” 

The study is published in the journal Molecular Biology and Evolution.

By Andrei Ionescu, Staff Writer

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