Formation of pigment cell patterns in Triturus alpestris embryos

The distribution of melanophores and xanthopores in developing tailbud stages of Triturus alpestris was investigated. In stage 27 embryos (curved tailbuds), melanophores are distributed evenly but sparsely over the entire dorsolateral trunk. With progressive development melanophores arrange themselves into compact dorsal and lateral bands present in stage 34 embryos (9 to 10-mm-long larvae). On the inner surface of detached pieces of skin from early tailbuds which were investigated in the scanning electron microscope xanthophores were discovered in addition to and mixed with melanophores. Unlike melanophores they are invisible from outside. Later in development they occupy the zone between the melanophore bands and also the dorsal fin. Thus, formation of pigment cell patterns in Triturus embryos is a process which seems to depend on the differential sorting out of two populations of neural crest-derived chromatophore cell types.