Unraveling Iridescence: Molecular biologists clarify how specialized cells in squid skin are able to control the animal’s coloration
Flashing calamari? The California market squid (Doryteuthis opalescens) has amazing light-manipulating abilities. While this species shares the gift of camouflage with most other cuttlefish, octopus and squid in the cephalopod family, it can also communicate and signal underwater through intricate changes in the patterns of color flashing from its skin. New research conducted in the lab of MCDB professor Daniel Morse demonstrates that the squid’s ability to “tune” its colors is driven by neurotransmitter-activated changes in phosphorylation of specific sequences of reflectins, proteins unique to the light-reflecting tissue of cephalopods. The findings open a new path to protein-encoded tunable properties, and appear in the Journal of Biological Chemistry.
Image: Dynamically tunable color of cells in squid skin: Activation with a droplet of the neurotransmitter, acetylcholine, induced a wave of color to ripple through the skin from top to bottom. The individual cells progressively reflected first red, then orange, yellow, green, and then blue, as proteins in the intracellular Bragg lamellae condensed to drive the activation of reflectance and progressively shrink the thickness and spacing of the lamellae, thus changing the color of the reflected light. The squid can selectively tune the cells to reflect any color, with the process being quickly reversible and readily cyclable. (Each object shown is a single cell, ca. 10 micrometers long; the dark spot in the center of each cell corresponds to the position of the nucleus.)