Chromatophores and their rôle in color change in the marine isopod idotea montereyensis (Maloney)

Abstract

Chromatophore response in Idotea montereyensis (Maloney) is closely linked to color variety. When green animals with chromatophores that have fully dispersed pigment are placed on differently colored backgrounds they concentrate the pigment in their chromatophores, maximal concentration occurring within 30 min. The degree of concentration is dependent on the level of light reflected from the substratum. Pigment dispersion is exceedingly slow in these animals. The overall result is the maintenance of highly punctate chromatophores when on a green substratum. Red animals likewise respond to reflected light and, like green animals, concentrate their chromatophore pigments so that the fullest concentration occurs within 30 min but soon after, the chromatophore pigment re-disperses to a stage not far distant from the original state. In both color varieties, chromatophores may also change relative to incident light, but the change is small compared to the influence of reflected light. The chromatophore changes that occur under natural conditions are discussed. The chromatophore differences seen in the two color varieties are highly adaptive allowing green animals to show their green cuticular coloration to full advantage and allowing red animals to closely adapt their color to a wide variety of different shades of red algae. The difference in mechanism provides a means of keeping the color varieties of the population separate and allowing only those exchanges that are highly adaptive to the population as a whole.