Tuesday, March 8, 2016

[Ornithology • 2016] Nondestructive Raman Spectroscopy confirms Carotenoid-pigmented Plumage in the Pink-headed Duck Rhodonessa caryophyllacea


FIGURE 1. Dorsal view of a Pink-headed Duck (Rhodonessa caryophyllacea, USNM 608914), close view of the pink crown feathers, and a Raman spectrum collected from the pink feathers. The Raman spectrum was collected at 100 mW for 60 s through a 10× microscope objective. Each of the 3 carotenoid-identifying peaks in the spectrum has been labeled with the vibrational mode it represents.

ABSTRACT
A small group of pigment classes is responsible for the wide range of plumage colors in modern birds. Yellow, pink, and other “warm” feather colors of many species are attributed to carotenoid pigments, a plumage trait that has an uneven distribution across modern bird species. Carotenoid plumage pigments are especially rare among fowl (superorder Galloanseres), and until recently, the Pink-eared Duck (Malacorhynchus membranaceus) from Australia provided the only evidence that any species of waterfowl (order Anseriformes) exhibits carotenoid-pigmented plumage. We analyzed a Pink-headed Duck (Rhodonessa caryophyllacea) study skin using Raman spectroscopy, without plucking or otherwise damaging the specimen. Raman spectra confirmed that the pink feathers of Rhodonessa are pigmented with carotenoids. Spectra from Rhodonessa were similar to those from Malacorhynchus, which suggests that the same carotenoid is the primary plumage pigment in both species. Moreover, spectra from Rhodonessa were similar to spectra from other taxa pigmented with ketocarotenoids. Malacorhynchus and Rhodonessa are distant relatives within Anseriformes, so these findings indicate multiple evolutionary origins of plumage carotenoids within the waterfowl or (less likely) many losses of plumage carotenoids from duck species. Our results show that pigment chemistry can be studied in precious ornithological specimens without damaging the specimens, and provide new evidence that the (apparently extinct) Rhodonessa possessed what is evolutionarily an extremely rare trait among waterfowl.

Keywords: Anseriformes, coloration, feather, pigmentation, Raman spectroscopy, Rhodonessa


Female and male Pink-headed Duck Rhodonessa caryophyllacea
illustrated by Henrik Grönvold  wikipedia.org


Daniel B. Thomas and Helen F. James. 2016. Nondestructive Raman Spectroscopy confirms Carotenoid-pigmented Plumage in the Pink-headed Duck [La espectrometría Raman no destructiva confirma la pigmentación con carotenoides del plumaje de Rhodonessa caryophyllacea].  The Auk. 133(2) 147-154. DOI: 10.1642/AUK-15-152.1

Extinct pink-headed duck derived its unique color from carotenoids  http://phy.so/373134159 via @physorg_com
Carotenoid pigments make extinct duck a rare bird indeed http://smithsonianscience.si.edu/2016/03/red-headed-duck/

RESUMEN
Un pequeño grupo de clases de pigmentos es responsable del amplio rango de colores del plumaje en las aves modernas. Amarillo, rosa y otros colores “cálidos” de las plumas de muchas especies son atribuidos a los pigmentos carotenoides, un rasgo del plumaje que tiene una distribución desigual entre las especies de aves modernas. Los pigmentos carotenoides del plumaje son especialmente raros entre las aves de caza (superorden Galloanseres) y hasta hace poco, la especie Malacorhynchus membranaceus de Australia representaba la única evidencia de una especie de ave acuática (orden Anseriformes) con plumaje pigmentado con carotenoides. Analizamos una piel de estudio de Rhodonessa caryophyllacea usando espectrometría Raman sin perforar o dañar el espécimen. El espectro Raman confirmó que las plumas rosas de Rhodonessa están pigmentadas con carotenoides. Los espectros de Rhodonessa fueron similares a aquellos de Malacorhynchus, sugiriendo que el mismo carotenoide es el principal pigmento del plumaje en cada especie. Más aun, los espectros de Rhodonessa fueron similares a los espectros de otros taxa pigmentados con ceto-carotenoides. Malacorhynchus y Rhodonessa son parientes distantes adentro de los Anseriformes, indicando orígenes evolutivos múltiples de los carotenoides del plumaje adentro de las aves acuáticas, o (menos probable) muchas pérdidas de los carotenoides del plumaje en las especies de patos. Nuestros análisis muestran que la química de los pigmentos puede ser estudiada en especímenes ornitológicos valiosos sin dañarlos, y brinda nueva evidencia de que la especie (aparentemente extinta) Rhodonessa poseía lo que es un rasgo evolutivo extremadamente raro entre las aves acuáticas.

Palabras clave: Anseriformes, coloración, espectrometría Raman, pigmentación, plumas, Rhodonessa

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