How lizards got their skin colour patterns
Skin colour patterns in fishes, amphibians and reptiles are self-organised through interactions among three types of chromatophore cells. Surprisingly, multiple species of lizards exhibit a scale-by-scale colour pattern, some scales being black and other being green or yellow. Even more surprisingly, many scales switch from green/yellow to black and from black to green/yellow during the life of the animal.
In this new publication, Ebrahim Jahanbakhsh and Michel Milinkovitch in the Laboratory of Artificial & Natural Evolution (LANE) show that five divergent species of lizards have independently evolved dynamics of scale-by-scale skin colour patterning. These dynamics emerge from the superposition of the bumpy skin geometry (because of the presence of scales) with the self-organised segregation of chromatophore cells. The researchers further demonstrate that Reaction-Diffusion, Cellular Automaton and Lenz-Ising models predict, in all species, the statistical features of the patterns despite their substantially-different motifs, whereas Reaction-Diffusion better predicts exact scale-by-scale colours.
Finally, Jahanbakhsh and Milinkovitch show that residual scale-by-scale error is entirely explained by uncertainties in skin geometry and in colour measurements at the juvenile stage, making Reaction-Diffusion remarkably performant without the need to parametrise the profusion of variables at the nanoscopic and microscopic scales.
The article was published in the journal Current Biology on November 14, 2022 and made the cover of the Journal.
Five-minutes video abstract