PLoS Biology: Are fish aware of themselves?

The cleaner wrasse responds to a mirror reflection as self—but does this mean that fish are self-aware?

The ability to perceive and recognise a reflected mirror image as self is considered a hallmark of cognition across species. Now researchers from the Max Planck Institute for Ornithology in Radolfzell, the University of Konstanz, and Osaka City University report that cleaner wrasse respond to their reflection and attempt to remove marks on its body during the mirror test.