TEMPERATURE-SENSITIVE, PHYSIOLOGICALLY ACTIVE IRIDOPHORES IN THE LIZARD UROSAURUS-ORNATUS - AN ULTRASTRUCTURAL ANALYSIS OF COLOR-CHANGE

Iridophores, pigment cells that structurally reflect the blue color in belly-patch scales of the lizard Urosaurus ornatus, are shown to be p hysiologically active. The wavelengths of light reflected by these cel ls change in response to temperature and osmolarity. Transmission elec tron micrographs show that these color changes result from quantifiabl e changes in spacing between layers of reflecting platelets (crystal-c ontaining organelles) within these cells. Changes in reflecting platel et spacing at various temperatures and osmolarities explain observed c hanges in skin color. This is the first report of temperature-sensitiv e, physiologically active iridophores and a mechanism for rapid change of structurally derived color in an amniote.