PIGMENT CELL SIGNALING FOR PHYSIOLOGICAL COLOR-CHANGE

The cellular signalling pathways participating in physiological color change are reviewed, particularly in crustaceans, teleosts, amphibians , and reptiles. This review is an attempt to summarize what is known a nd to raise some hypotheses about basic questions still to be elucidat ed. The first picture that emerges from the literature is that the tra nsduction pathways are identical in the various types of chromatophore s of a single species, except for the iridophore. The cAMP-dependent p athway has been well conserved throughout evolution; cAMP increase is the pigment dispersion signal whereas the nucleotide decrease leads to granule aggregation. On the other hand, the Ca+2-dependent pathways e voke pigment aggregation in teleosts and crustaceans, and dispersion i n amphibians and probably reptiles as well. Another interesting point is the ultimate convergence of the signalling pathways of different ag onists inducing the same response in one chromatophore type. A hypothe sis is raised about why different chromatophores behave differently in the absence of agonists, that is, why some are punctate, whereas othe rs are stellate. (C) 1997 Elsevier Science Inc.