Jewel beetles are amazing insects, easily recognizable by their bright colors and metallic luster. Jewel beetles, which have large, well-developed eyes, use vision and coloration for a range of different behaviors, including finding mates and host plants.
Color vision in insects is different from ours. Special genes allow many insects to see ultraviolet light as well as blue and green. New research led by Camilla Sharkey, a postdoctoral fellow in Wardle’s lab in the School of Biological Sciences, looks into the complex evolutionary history of jewel beetle vision. The research team included Jorge Blanco, formerly of Wardill’s lab and now at the University of Maryland, Nathan Lord of Louisiana State University, and Trevor Wardill, assistant professor at CBS.
Previous research by Dr. Sharkey showed that before modern beetles evolved, their ancestors lost the ability to see blue light about 300 million years ago. This may be the result of the beetle’s ancestor becoming nocturnal or living in low-light conditions. Later, as the beetles diversified, they evolved duplicates of their ancestral genes that allow them to see ultraviolet light and the green spectrum. These duplicate genes can evolve further, making new parts of the color spectrum visible and allowing more complex and diverse color cues to be seen.
The researchers wanted to see if duplicate genes had evolved, allowing the beetles to see colors their ancestors could not. Since jewel beetles are difficult to keep in the lab, they copied the genes and inserted them into fruit flies, replacing their normal visual genes. Using electrophysiology, they tested the color sensitivity of each gene produced in the flies. Then they looked for genetic changes that might underlie changes in color sensitivity using 3D protein modeling. The study found that:
- Jewel beetles have evolved additional sensitivity to blue and orange by replicating and upgrading their UV and green visible genes.
- This enables tetrachromatic complex color sensitivity to wavelengths of ultraviolet, blue, green and orange light, similar to the color sensitivity of colored birds.
- Newly developed genetic changes related to color detection were not found to change sensitivities as expected when visual genes were modified and retested.
All species of jewel beetles studied to date contain four different types of genes that were isolated in the research, suggesting that perhaps all jewel beetles have complex color sensitivity. According to Sharkey, “The next step is to determine whether specific types of color vision can be predicted from genes and how color vision is used by insects to better manage insect pests and pollinators, and thus improve crop production.” The researchers also hope to understand the molecular basis of jewel beetle color sensitivity, which would provide a basis for predicting insect color sensitivity from gene sequencing.
Funding was provided by the National Science Foundation and the University of Minnesota College of Biological Sciences.
