One of the most famous and interesting subfamilies of damselfish (Pomacentridae) are species of anemonefish. They form dominant hierarchies with one sexually matured pair and subdominant males; ones the dominant female dies, the most dominant male will become a female. Making use of modern molecular, neuroanatomical and physiological approaches, we study visual adaptation on the level of photoreceptors and their intrinsic light absorbing visual pigment genes (opsins) by comparing different anemonefish species:
Previous studies revealed that damselfish possess one rhodopsin (RH1) used for scotopic, and four cone opsins used for photopic vision being short- (SWS1 and SWS2B), medium- (RH2A and RH2B) and long-wavelength (LWS) sensitive. Using RNA sequencing, we compared the cone opsin expression in five species of anemonefish (Amphiprion akindynos, A. melanopus, A. percula, A. perideraion, and Premnas biaculatus): all species expressed SWS1, RH2B, RH2A, and LWS. Interestingly, the expression of LWS was prominent in all species but low in A. akindynos, possibly reflecting different foraging styles. By comparing a wider range of damselfish species, we could already demonstrate that an increased LWS-expression is correlated to herbivory. More strikingly, we found that the UV-sensitive SWS1 has duplicated in anemonefish with different species expressing different or both copies. Analysis now underway indicate that this duplication event is widespread across the damselfish phylogeny underpinning the importance of UV-vision in damselfish. Making use of FISH and state-of-the-art microscopy (Discovery Spinning Disc Confocal) we currently produce whole retinal maps visualizing expressed opsin genes to further examine visual adaptations in anemonefish.