Reef fish get riled when intruders glow red
Male fairy wrasses get feisty when a rival fluoresces
RED MESSAGE In the mostly blue world of a coral reef, a male fairy wrasse (left, illuminated with white light) will take note when one of its kind sports a fluorescent red glow (right, under blue light).
T. Gerlach et al/Proc. Roy. Soc. B. 2014