Meeting Abstract
Dynamic coloration is the ability of certain animals to rapidly change the color of the body. Physiological investigation of this system has led to the hypothesis that color change, often for the purpose of camouflage, may at least be partially mediated by a light-sensing mechanism in the skin. The present work is the first to show that instead of serving as an environmental sensor, light reception by the skin may instead underlie a sensory feedback mechanism for color change. Here, the functional organization of dermal photoreception was investigated in the hogfish (Lachnolaimus maximus), a reef fish that undergoes dynamic coloration. In part, hogfish achieve skin color change via well-characterized movements of pigment granules within specialized cells called chromatophores. These pigment granules absorb short-wavelength light, dispersing and aggregating along a two-dimensional plane, giving hogfish their reddish-brown and pale-white color morphs, respectively. Here, transcriptomics revealed the expression of genes that could support distinct, yet complete phototransduction cascades in the retina and skin of L. maximus. In contrast to the genes encoding five opsin classes and a cGMP-dependent phototransduction cascade in the retina, a single short-wavelength sensitive opsin (SWS1) and putative cAMP-dependent phototransduction cascade were found in the skin. Anti-opsin immunofluorescence localized the SWS1 opsin underneath the layer of pigment within chromatophore cells. As such, aggregated pigment would allow incident light to activate the skin’s SWS1 opsin, while dispersed pigment would obscure incident light, causing deactivation of the opsin during the skin’s color-change response. This feedback mechanism could provide information about how the skin appears, in lieu of the animal observing its own body, to optimize color-change performance.
