title: Structural colour in Chondrus crispus.
abstract: The marine world is incredibly rich in brilliant and intense colours. Photonic structures are found in many different species and provide extremely complex optical responses that cannot be achieved solely by pigments. In this study we examine the cuticular structure of the red alga Chondrus crispus (Irish Moss) using anatomical and optical approaches. We experimentally measure the optical response of the multilayer structure in the cuticle. Using finite-difference time-domain modelling, we demonstrate conclusively for the first time that the dimensions and organisation of lamellae are responsible for the blue structural colouration on the surface of the fronds. Comparison of material along the apical-basal axis of the frond demonstrates that structural colour is confined to the tips of the thalli and show definitively that a lack of structural colour elsewhere corresponds with a reduction in the number of lamellae and the regularity of their ordering. Moreover, by studying the optical response for different hydration conditions, we demonstrate that the cuticular structure is highly porous and that the presence of water plays a critical role in its ability to act as a structural light reflector.
authors.affiliation: Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, UK.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Chandler
authors.affiliation: Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
authors.forename: Bodo D
authors.initials: BD
authors.lastname: Wilts
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
authors.forename: Silvia
authors.initials: S
authors.lastname: Vignolini
authors.affiliation: Natural History Museum, Department of Life Sciences, Genomics and Microbial Diversity Division, Cromwell Road, London, SW7 5BD, UK.
authors.forename: Juliet
authors.initials: J
authors.lastname: Brodie
authors.affiliation: Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
authors.forename: Ullrich
authors.initials: U
authors.lastname: Steiner
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Rudall
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
authors.forename: Beverley J
authors.initials: BJ
authors.lastname: Glover
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gregory
authors.affiliation: Natural History Museum, Department of Life Sciences, Genomics and Microbial Diversity Division, Cromwell Road, London, SW7 5BD, UK.
authors.forename: Rachel H
authors.initials: RH
authors.lastname: Walker
mesh_terms: D044723:Chondrus / Q000378:metabolism / Q000648:ultrastructure*; D003890:Desiccation; D046529:Microscopy, Electron, Transmission; D010858:Pigmentation