Salamander pigment patterns: how can they be used to study developmental mechanisms and their evolutionary transformation?

Neural crest cells of ectothermic vertebrates give rise to three types of pigment cells: melanophores, xanthophores, and iridophores. In early larval salamanders, these cells can combine to generate a variety of pigment patterns across taxa, including vertical bars and horizontal stripes. Such patterns offer an opportunity to study neural crest morphogenesis and differentiation, as well as the evolution of these processes and the morphologies that arise from them. This review examines the phylogenetic distribution of specific pigment patterns, our current understanding of the mechanisms underlying these patterns, and how evolutionary transformations of these mechanisms may have resulted in alternative pigment patterns across taxa.