Several years ago it was revealed that damselfish could see specially colored markings on the faces of other fish that only show up under ultraviolet light. Now a new study has demonstrated that the fish can not only see these UV face markings, but they can also recognize the unique pattern of those ultraviolet markings.
It was quite a surprise when we learned that our pugnacious aquarium damselfish can see certain wavelengths of ultraviolet light, and that they developed special ‘bridles’ of ultraviolet color on their faces. But now we know that those markings can be recognized, and it opens up a whole slew of more questions about the social lives of damselfishes.
Behavioral researchers studying the ambon damselfish, Pomacentrus amboinensis, trained some of their subjects to pick at unique facial markings to get a reward for food. The facial recognition system of damselfishes was also quite nuanced as they were able to distinguish between closely resembling facial markings.
These new findings about damselfish UV facial marking recognition is likely used for mate recognition and to generally build up a local social order between these non-roaming species of reef fish. More interestingly, many different species of damselfishes have very closely matching color patterns and only genetic analysis has been able to differentiate cryptic species any further.
So far the UV face markings has mostly been studied in Pomacentrus damselfishes which have blue to light purple face marks that are visible to the naked eye. Since sophisticated aquarium LED lights now include a nice healthy dose of UV light which is independently controllable. Us reefers could tap into this feature to recognize our own damselfish, but probably only with the use of special filters as humans can’t distinguish UV light. [NatGeo]