Scientists find genetic switch that expanded butterflies’ colour vision

A butterfly's world is not simply brighter or more colourful than ours. It is built from a richer visual vocabulary, one shaped by an evolutionary tweak hidden deep inside its compound eyes. While most insects have spent hundreds of millions of years working with a familiar visual blueprint, butterflies took a different route, adding an extra light-sensing cell to every tiny visual unit. Now, researchers at the University of California San Diego have identified the genetic switch that made this unusual upgrade possible.The eye that broke the mouldAccording to the UC San Diego website, compound eyes are made up of hundreds of tiny units, each containing a cluster of photoreceptors that detect light. In most insects, including flies, each unit contains eight such cells, arranged in a remarkably conserved pattern. Butterflies are different. Their eye units contain nine photoreceptors, giving them access to a broader range of colour information.