Phenotypic plasticity in anemonefishes: An Eco/Evo/Devo analysis

Abstract

Determining how plasticity of developmental traits respond to environmental conditions is a challenge that must combine evolutionary sciences, ecology and developmental biology. Developmental plasticity is defined as the ability of an organism to adjust its development depending on environmental signals, thus producing alternative phenotypes precisely adjusted to the environment. Yet the mechanisms underlying developmental plasticity are not fully understood yet. Determining how plastic developmental changes that occur in response to environmental conditions are coordinated at the physiological, cellular, and molecular levels is a challenge that must combine ecology with developmental biology. The mechanisms that underlie the development of alternative phenotypes are still unclear for many systems and is one major goal of ecological developmental biology or Eco-Evo-Devo. We observed that clownfish (Amphiprion percula) young juveniles have a different rate of white bar formation depending on the sea anemone species, their obligate symbiotic partner, in which they are recruited: white bars develop more rapidly when fish are recruited in Stichodactyla gigantea than in Heteractis magnifica. Because the sister species A. ocellaris acquire their adult color pattern during metamorphosis under thyroid hormone (TH) control, we asked whether developmental plasticity in bar formation was associated with alteration in TH status as these are the main hormones triggering metamorphosis in vertebrates. We found that thyroid hormones regulate white bar formation and that a shift in hormone levels, associated with ecological differences, results in divergent color patterns in different sea anemone species in which the young fish is recruited. Taken together our results suggest that TH control the timing of adult color pattern formation and that shifts in gene expression and TH levels are associated with ecological differences resulting in divergent ontogenetic trajectories in color pattern development. We recently observed that the phenotypic change observed not only concerns pigmentation but also energy metabolism. The evolutionary implications of these observations will be discussed