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    The evolution of carotenoid-based plumage colours in passerine birds
    (John Wiley and Sons Ltd on behalf of British Ecological Society, 2023-01-04) Delhey K; Valcu M; Dale J; Kempenaers B; Willink B
    1. Many birds use carotenoids to colour their plumage yellow to red. Because birds cannot synthesise carotenoids, they need to obtain these pigments from food, although some species metabolise dietary carotenoids (which are often yellow) into derived carotenoids (often red). 2. Here, we study the occurrence of yellow and red carotenoid-based plumage colours in the passerines, the largest bird radiation and quantify the effects of potential ecological and life-history drivers on their evolution. 3. We scored the presence/absence of yellow and red carotenoid-based plumage in nearly 6,000 species and use Bayesian phylogenetic mixed models to assess the effects of carotenoid-availability in diet, primary productivity, body size, habitat and sexual selection. We also test the widespread assumption that red carotenoid-based colours are more likely to be the result of metabolization. Finally, we analyse the pattern of evolutionary transitions between yellow and red carotenoid-based plumage colours to determine whether, as predicted, the evolution of yellow carotenoid-based colours precedes red. 4. We show that, as expected, both colours are more likely to evolve in smaller species and in species with carotenoid-rich diets. Yellow carotenoid-based plumage colours, but not red, are more prevalent in species that inhabit environments with higher primary productivity and closed vegetation. In general, females were more likely to have yellow and males more likely to have red carotenoid-based plumage colours, closely matching the effects of sexual selection. Our analyses also confirm that red carotenoid-based colours are more likely to be metabolised than yellow carotenoid-based colours. Evolutionary gains and losses of yellow and red carotenoid-based plumage colours indicate that red colours evolved more readily in species that already deposited yellow carotenoids, while the reverse was rarely the case. 5. Our study provides evidence for a general, directional evolutionary trend from yellow to red carotenoid-based colours, which are more likely to be the result of metabolization. This may render them potentially better indicators of quality, and thus favoured by sexual selection.
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    Validity and reliability of Raman spectroscopy for carotenoid assessment in cattle skin
    (Elsevier BV, 2021-09) Mehta M; Naffa R; Zhang W; Schreurs NM; Waterland M; Cooper S; Holmes G
    Carotenoids are powerful antioxidants capable of helping to protect the skin from the damaging effects of exposure to sun by reducing the free radicals in skin produced by exposure to ultraviolet radiation, and they may also have a physical protective effect in human skin. Since carotenoids are lipophilic molecules which can be ingested with the diet, they can accumulate in significant quantities in the skin. Several studies on humans have been conducted to evaluate the protective function of carotenoids against various diseases, but there is very limited published information available to understand the mechanism of carotenoid bioavailability in animals. The current study was conducted to investigate the skin carotenoid level (SCL) in two cattle skin sets - weaners with an unknown feeding regime and New Generation Beef (NGB) cattle with monitored feed at three different ages. Rapid analytical and sensitive Raman spectroscopy has been shown to be of interest as a powerful technique for the detection of carotenoids in cattle skin due to the strong resonance enhancement with 532 nm laser excitation. The spectral difference of both types of skin were measured and quantified using univariate and linear discriminant analysis. SCL was higher in NGB cattle than weaners and there is a perfect classification accuracy between weaners and NGB cattle skin using carotenoid markers as a basis. Further work carried out on carotenoid rich NGB cattle skin of 8, 12 and 24 months of age identified an increasing trend in SCL with age. The present work validated the ability of Raman spectroscopy to determine the skin carotenoid level in cattle by comparing it with established HPLC methods. There is an excellent correlation of R2 = 0.96 between the two methods that could serve as a model for future application for larger population studies.
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    Investigating patterns of avian ornamental colouration : intraspecific and interspecific approaches : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Zoology at Massey University, Albany, New Zealand
    (Massey University, 2019) Ahlstrom, Millie Beatrice May
    Research into the evolutionary function of elaborated colouration in birds is continually ongoing. Novel approaches to addressing various aspects of this broad research area may help us consider this topic in a new light. This thesis aimed to consider two different aspects of avian colouration research using novel methods and testing relatively new hypotheses. Firstly, I consider the cost of carotenoid pigmented ornamental colouration - an area of research that is currently under intense debate. Classically carotenoid-based pigmentation has considered carotenoids to function as indicators of sexual quality, with costs being due to carotenoids being diet dependent in birds. Recent research however has argued that carotenoid pigmented colour traits function in agonistic social contexts, and that the cost of using carotenoid pigmentation as an honest indicator of quality is a social one. In this study I test this hypothesis using blackbirds (Turdus merula) and their natural variation in carotenoid-based bill colouration. I replicate a study using model presentations to simulate territory intrusions. Additionally, I examine the feasibility of using three-dimensionally printed models in avian behavioural studies. This study was unsuccessful due to a lack of response rates from territorial males, however it was successful in questioning several differing aspects between my study and the study I replicated. Secondly, I explore the spatial organisation of colouration on the bodies of birds as a way of potentially inferring different functions of elaborate colour traits. In the third chapter I develop a novel method that allows objective analysis of the spatial organisation of colour on the bodies of birds, by removing morphological variation between species. Using this method I present a case study on the spatial organisation of colour elaboration in 2,471 species of passerines. This case study uses a difference in sexual dichromatism as a proxy for colour elaboration and determined where signaling hotspots occur on the bodies of birds. These results demonstrate that conspicuous colouration is most common in the supercilium, chin, and upper breast of passerine birds. In chapter four, I used this method to determine correlations between different life-history traits and different regions of the body. This study aimed to infer the function of different regions of the head in signaling. My results show that the irises in species with tropical life-histories and cooperative breeding strategies are more likely to be elaborately coloured; bills of larger bodied species are more likely to be elaborately coloured than are smaller species; and the spatial organisation of colour effects females more than it does males.
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    Regulation of the carotenoid biosynthetic pathway in petals of California poppy (Eschscholzia californica) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Zhou, Jun
    Carotenoids are essential plant pigments. They function in a wide range of processes including light harvesting in the photosynthetic apparatus, photoprotection against light damage, and pigmentation in flowers and fruits to attract pollinators and seed-dispersal herbivores. Carotenogenesis has been studied extensively in the last century in both photosynthetic and non-photosynthetic tissues of many plant species. Although most of the enzymes and their metabolites of the pathway have been identified, little is still known about how carotenoid production is regulated. Previous studies have proposed that regulation of the carotenoid pathway is through metabolite feedback occurring at both transcriptional and post transcriptional levels. This thesis examines the evidence for carotenogenesis gene transcription being feedback regulated by changes in carotenoid metabolites in petals of California poppy (Eschscholzia californica), and if so, by which metabolite(s). Virus-induced gene silencing (VIGS) was used to silence carotenoid biosynthetic genes in the petals of orange California poppy. High efficacy of silencing was achieved by first infiltrating and then drenching the California poppy seedlings with the Agrobacterium tumefaciens strain GV3101 containing the VIGS vectors. The VIGS vectors included portions of carotenoid gene fragments isolated from California poppy. qRT-PCR confirmed that transcript abundance of the targeted carotenogenesis genes EcaPDS, EcaZDS, EcaLCYb, EcaCHYb and EcaZEP was significantly reduced in the flower petals. Reduced transcript abundance of all genes apart from EcaLCYb altered flower colour. HPLC analyses revealed that the colour altered flower petals with knocked-down expression of each targeted gene resulted in a reduction of total carotenoid content and an altered profile of carotenoids. This manifested as an accumulation of higher amounts of intermediates including phytofluene, ζ-carotene, β-carotene and zeaxanthin, some of which are not usually seen in the flowers, and a reduction of the end products such as retro-carotene-triol and eschscholtzxanthin. However, these alterations in carotenoid profiles were not associated with any dramatic changes in transcript abundance of the non-TRV-targeted endogenous genes in the pathway. Therefore, little evidence was found for metabolite feedback regulation of transcriptional activity in the carotenoid biosynthetic pathway from this study. Other possible mechanisms for controlling carotenogenesis are discussed.
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    Studies on carotenoid metabolism : being a thesis submitted to the University of New Zealand in partial fulfilment of the requirements for the degree of Doctor of Philosophy
    (Massey University, 1957) Worker, N. A.
    Studies on various aspects of carotenoid metabolism have been carried out in the Biochemistry Department now for a number of years. A considerable fillip was given this work in 1954 with the return of Dr. W.A. McGillivray from study leave overseas spent at the National Institute for Research in Dairying at Shinfield, Working in collaboration with Dr. S.K. Kon and Dr. S.Y. Thompson, two senior British workers in the field; and again in 1955 with the reciprocal visit of the latter worker to this laboratory for a period of some nine months. The work reported in this thesis was carried out in the department between April 1955 and June 1957 during which time two separate investigations on different aspects of carotenoid metabolism were undertaken. The first of these was concerned with a study of the utilization of parenterelly administered carotenoids, Particularly in small animals, and the other with experiments on factors affecting the carotenoid and vitamin A contents of milk fat, in particular, on factors affecting the summer decline in the carotenoid and vitamin A contents of New Zealand milk fat. In order to facilitate the presentation of the results of these investigations, the work is reported in two separate sections.