LAUSR

Significance Some animals have the capacity for mirror self-recognition, but implications for self-awareness remain controversial. Here, we show that cleaner fish, Labroides dimidiatus, likely recognize their own mirror image using a mental image of the self-face comparable to humans. Mirror-naïve fish frequently attacked photographs of both themselves and strangers. In contrast, after passing the mirror test, aggression against their own photograph and composite photographs of own face/stranger body declined, but aggression remained toward unfamiliar and composite photographs of stranger face/own body. Our results suggest that cleaner fish with MSR ability can recognize their own mirror image based on a mental image of their own face, rather than by comparing body movements in the mirror. This study demonstrates how animals recognize self-images.