Circuit mechanisms for colour vision in zebrafish.

The use of spectral information in natural light to inform behaviour is one of the oldest and most fundamental abilities of visual systems. It long-predates animals' venture onto the land, and even the appearance of image-forming eyes. Accordingly, circuits for colour vision evolved under the surface of ancient oceans for hundreds of millions of years. These aquatic beginnings fundamentally underpin, and likely constrain, the organisation of modern visual systems. In contrast to our detailed circuit level understanding from diverse terrestrial vertebrates, however, comparatively little is known about their aquatic counterparts. Here, I summarise some of what is known about neural circuits for colour vision in fish, the most species-diverse group of vertebrates. With a focus on zebrafish, I will explore how their computational strategies are linked to the statistics of natural light in the underwater world, and how their study might help us understand vision in general, including in our own eyes.