Abstract :
[en] Coral reef fishes provide classical examples of complex colour patterns exhibiting a huge diversity. Most of these species display spots, stripes, repeated lines, eyespots, grids, etc. This diversity in colour patterns might serve for species recognition, camouflage, mimicry and/or warning. To date, work have mainly been focused on the link between colour patterns, ecology and behavior, that is the ultimate role of these patterns. However, the underlying development and cellular mechanisms controlling these patterns and their evolution, that is their proximal mechanisms, are still largely unknown. To address this question, we are using a well-known coral-reef fish models, anemonefishes (Amphiprion and the monotypic Premnas). This tribe (Amphiprionini) within the Pomacentridae is composed of 30 species that display a relatively simple colour pattern made of 0-3 white stripes that are well visible on a yellow to red, brown or even black body background. This simple colour pattern offers a unique opportunity to better delineate the pattern and processes allowing the diversification of such diversity. Here, we focus on the vertical white stripes present in most species of Amphiprion. We first map their striped patterns on the anemonefish evolutionary tree and reconstruct the ancestral state. Our results provide evidences that the diversification in colour pattern in anemonefish results from successive losses of stripes during evolution. Then, by an ontogenetic study, we show that larvae stripes always appear from rostral to caudal. Interestingly, larvae of some species such as A. frenatus have surplus stripes (with a maximum of three stripes) which disappear caudo-rostrally during the juvenile phase to acquire their adult color pattern. The reduction of stripes number over ontogeny totally matches the sequences of stripe losses across evolution. This demonstrates that the diversification in colour pattern among anemonefish lineages results from changes in developmental processes. Finally, assuming that the number of stripes may be related to the species ecology, we further determined the links between the number of stripes and ecomorphological traits. Together, this innovative study allows to understand how developmental processes are shaping the diversification of color pattern of anemonefishes and how it may be related with ecomorphological traits evolution.