1 2 3 Visual phototransduction components in cephalopod chromatophores suggest dermal 4 photoreception 5 6 Alexandra C. N. Kingston1, Alan M. Kuzirian2, Roger T. Hanlon2, and Thomas W. Cronin1 7 1Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop 8 Circle, Baltimore, Maryland 21250 USA 9 2Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA 10 11 Corresponding Author: 12 Thomas W. Cronin 13 Department of Biological Sciences 14 University of Maryland Baltimore County 15 Baltimore, MD 21250 16
[email protected] 17 410-455-3449 18 19 Key words: rhodopsin, retinochrome, extraocular photoreceptor, skin 20 21 Running title: Squid dermal phototransduction machinery 22 23 Abstract 24 Cephalopod molluscs are renowned for their colorful and dynamic body patterns, produced by an 25 assemblage of skin components that interact with light. These may include iridophores, 26 leucophores, chromatophores, and (in some species) photophores. Here, we present molecular 27 evidence suggesting that cephalopod chromatophores, small dermal pigmentary organs that 28 reflect various colors of light, are photosensitive. RT-PCR revealed the presence of transcripts 29 encoding rhodopsin and retinochrome within the retinas and skin of the squid Doryteuthis 30 pealeii, and the cuttlefish Sepia officinalis and Sepia latimanus. In D. pealeii, Gqα and squid 31 TRP channel transcripts were present in the retina and in all dermal samples. Rhodopsin, 32 retinochrome, and Gqα transcripts were also found in RNA extracts from dissociated 33 chromatophores isolated from D. pealeii dermal tissues. In D. pealeii, immunohistochemical 34 staining labeled rhodopsin, retinochrome, and Gqα proteins in several chromatophore 35 components, including pigment cell membranes, radial muscle fibers, and sheath cells.