Figure 7
Model for evolutionary changes in danio pigment cell lineages. In embryos, neural crest cells differentiate into a diverse array of cell types including early larval melanophores (ELM) and early larval xanthophores (ELX). Additional cells are hypothesized to serve as stem cells (m) that can be recruited to differentiate during metamorphosis. During the larval-to-adult transformation of D. rerio, relatively few early larval melanophores persist into adult stripes and instead numerous metamorphic melanophores (MM) and metamorphic xanthophores (MX) are recruited. Interactions within and among pigment cell classes contribute to stripe formation (schematized by hatch marks on MX and MM), as do other presently unknown cues required for setting positions and orientations of stripes. In D. nigrofasciatus, more ELM persist and fewer MM develop owing to an early block in the metamorphic melanophore lineages that also affects undifferentiated melanoblasts (MB). In D. albolineatus, there are more xanthophores and fewer metamorphic melanophores than in D. rerio, as well as hypothesized differences in pigment cell interactions.
