they can distinguish their own face from others
Cleaner fish have demonstrated an impressive level of intelligence by passing the mirror test, a test which only a handful of non-human animals, such as orcas, chimps and magpies, have been able to pass. Additionally, they are able to recognize their own faces in photos. Researchers believe that this ability is a result of their territorial nature, as they will attack intruders, but will not attack their own face regardless of the body it is on. This shows that they are able to distinguish their own face from others.