http://ecoworldly.com/2008/10/07/sci...greatest-lake/In a report published in the journal Nature, researchers from Tokyo’s Institute of Technology and the Swiss Federal Institute of Aquatic Science and Technology have observed the cichlid evolve into a new species better adapted in sighting its prey and predator.
Researchers looked at two species, conspicuous by their red or blue colours. They determined through lab experiments that certain genetic mutations helped some fish adapt their vision at deeper levels to see the colour red and others in shallower water to recognise shades of blue.
The researchers showed that the eyes have adapted to this difference so that fish that live in deeper water have a pigment in their eyes that is more sensitive to red light, while shallow-water fish were sensitive to blue.
I thought DF would find this article interesting. I think Cichlid's are already interesting because of their close relationship with salt water fish.