title: Identification of Shell Colour Pigments in Marine Snails Clanculus pharaonius and C. margaritarius (Trochoidea; Gastropoda).
abstract: Colour and pattern are key traits with important roles in camouflage, warning and attraction. Ideally, in order to begin to understand the evolution and ecology of colour in nature, it is important to identify and, where possible, fully characterise pigments using biochemical methods. The phylum Mollusca includes some of the most beautiful exemplars of biological pigmentation, with the vivid colours of sea shells particularly prized by collectors and scientists alike. Biochemical studies of molluscan shell colour were fairly common in the last century, but few of these studies have been confirmed using modern methods and very few shell pigments have been fully characterised. Here, we use modern chemical and multi-modal spectroscopic techniques to identify two porphyrin pigments and eumelanin in the shell of marine snails Clanculus pharaonius and C margaritarius. The same porphyrins were also identified in coloured foot tissue of both species. We use high performance liquid chromatography (HPLC) to show definitively that these porphyrins are uroporphyrin I and uroporphyrin III. Evidence from confocal microscopy analyses shows that the distribution of porphyrin pigments corresponds to the striking pink-red of C. pharaonius shells, as well as pink-red dots and lines on the early whorls of C. margaritarius and yellow-brown colour of later whorls. Additional HPLC results suggest that eumelanin is likely responsible for black spots. We refer to the two differently coloured porphyrin pigments as trochopuniceus (pink-red) and trochoxouthos (yellow-brown) in order to distinguish between them. Trochopuniceus and trochoxouthos were not found in the shell of a third species of the same superfamily, Calliostoma zizyphinum, despite its superficially similar colouration, suggesting that this species has different shell pigments. These findings have important implications for the study of colour and pattern in molluscs specifically, but in other taxa more generally, since this study shows that homology of visible colour cannot be assumed without identification of pigments.
authors.affiliation: Natural History Museum, Department of Life Sciences, London, United Kingdom.
authors.forename: S T
authors.identifier: http://orcid.org/0000-0003-2995-5823
authors.initials: ST
authors.lastname: Williams
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Wakamatsu
authors.affiliation: Natural History Museum, Imaging and Analysis Centre, London, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Goral
authors.affiliation: School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: N P
authors.initials: NP
authors.lastname: Edwards
authors.affiliation: School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: R A
authors.initials: RA
authors.lastname: Wogelius
authors.affiliation: School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Henkel
authors.affiliation: NEEM Núcleo de Espectroscopia e Estrutura Molecular, Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil.
authors.forename: L F C
authors.initials: LF
authors.lastname: de Oliveira
authors.affiliation: NEEM Núcleo de Espectroscopia e Estrutura Molecular, Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil.
authors.forename: L F
authors.initials: LF
authors.lastname: Maia
authors.affiliation: Natural History Museum, Imaging and Analysis Centre, London, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Strekopytov
authors.affiliation: Natural History Museum, Imaging and Analysis Centre, London, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Jeffries
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, United States of America.
authors.forename: D I
authors.initials: DI
authors.lastname: Speiser
authors.affiliation: Viapath, Reference Biochemistry Laboratories, King's College Hospital, London, United Kingdom.
authors.forename: J T
authors.initials: JT
authors.lastname: Marsden
mesh_terms: D060105:Animal Shells / Q000378:metabolism*; D000818:Animals; D010858:Pigmentation; D010860:Pigments, Biological / Q000378:metabolism; D012908:Snails / Q000033:anatomy & histology* / Q000378:metabolism*
chemical_list: D010860:Pigments, Biological