Biotechnological applications of research on animal pigmentation

Effects of different types of xanthophyll extracted from marigold on pigmentation of yellow-feathered chickens

OBJECTIVE

This study aimed to explore the effects of different types of xanthophyll extracted from marigold on the growth performance, skin color, and carcass pigmentation.

METHODS

A total of 192 healthy 60-day-old yellow-feathered broilers weighing an average of 1,279±81 g were randomly allocated to 4 groups, each with 6 replicates and 8 broilers. The 4 treatments were as follows: i) CON group, fed with basal diet; ii) LTN group, supplemented with lutein; iii) MDP group, supplemented with monohydroxyl pigment including dehydrated lutein, β-cryptoxanthin, and α-cryptoxanthin; iv) LTN+MDP group, supplemented with lutein and monohydroxyl pigment in proportion to 1:1. The supplementary content of LTN, MDP, and LTN+MDP was 2 g/kg. Skin color was measured after 7, 14, 21, and 28 days of feeding the dietary treatments. The breast, thigh, and abdominal fat of slaughtered chickens were stored in cold storage at 4°C for 24 hours and then the meat color of lightness (L*), redness (a*), and yellowness (b*) values was determined.

RESULTS

The results showed that all treatments enhanced the yellow scores of subwing skin on day 14, 21, and 28 (p<0.05), and the mixture of lutein and monohydroxyl pigment promoted the yellow scores of shanks on day 14, 21, and 28 (p<0.05). The mixture of lutein and monohydroxyl pigment increased the yellow scores of beaks and all treatments enhanced the yellow of shanks on day 28 (p<0.05). In addition, all treatments improved the yellow (b*) values of breast and thigh muscle, moreover, the monohydroxyl pigment and the mixture of lutein and monohydroxyl pigment enhanced the values of redness (a*) and yellow (b*) of abdominal fat (p<0.05).

CONCLUSION

In summary, different types of xanthophyll extracted from marigold significantly increased the yellow scores of skin color and the yellow (b*) values of carcass pigmentation. Especially, the mixture of lutein and monohydroxyl pigment was more efficient on skin color.

Brightened body coloration in female guppies (Poecilia reticulata) serves as an in vivo biomarker for environmental androgens: The example of 17β-trenbolone

In vivo testing systems for environmental androgens are scarce. The aim of this study was to evaluate the potential of male-specific brightened body coloration in female guppies (Poecilia reticulata) to serve as an in vivo biomarker of environmental androgens using 17β-trenbolone as an example. The high bioaccumulation of 17β-trenbolone in the skin of female guppies suggests that it is a potential target tissue of environmental androgens. The coloration index, pigment cell ultrastructure, pigment levels, sexual attractiveness, and reproductive capability of female guppies were analyzed following 28 days of exposure to 20 ng/L, 200 ng/L, and 2000 ng/L 17β-trenbolone. Increases in the coloration index caused by 17β-trenbolone exposure were attributable to increased pteridine and melanin levels. Decreases in the sexual attractiveness, number of offspring, and survival rate of offspring suggested that the changes in body coloration translated into adverse outcomes. Finally, mRNA sequencing indicated that 17β-trenbolone increased pteridine levels by activating genomic effects of androgen receptor on xanthine dehydrogenase and increased melanin levels by exerting non-genomic effects targeting microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein 1 that were mediated by mitogen-activated protein kinase and calcium signaling pathways. We have derived a robust adverse outcome pathway of environmental androgens, and our findings suggest that indicators at different biological levels related to brightened body coloration in female guppies can serve as less-invasive or noninvasive in vivo biomarkers of short-term exposure to environmental androgens.

Effect of Natural and Chemical Colorant Supplementation on Performance, Egg-Quality Characteristics, Yolk Fatty-Acid Profile, and Blood Constituents in Laying Hens

Natural and chemical colorants are attracting a lot of attention as sustainable feed additives due to their effect on food color and because presentation matters to consumers. Color also is a major sensory factor that helps consumers determine food quality and its possible health benefits. For example, highly colored egg yolks can only come from healthy laying hens fed a well-balanced, nutrient-rich diet. Consumers associate an intense yolk color with healthy, nutrient-rich food. There is a growing market request for eggs with rich yolk coloring. The purpose of the current study was to evaluate the impact of natural (paprika) and chemical (carmoisine) colorant supplementation on the performance, egg-quality characteristics, yolk fatty-acid profile, and blood constituents in laying hens. A total of 240 Bovans laying hens were randomly distributed in a completely randomized design in four treatments according to four experimental diets: a control diet (without supplementation of any colorants), a control diet supplemented with 4 kg/ton paprika, a control diet supplemented with 150 g carmoisine/ton, and a control diet supplemented with a combination of 4 kg/ton paprika plus 150 g carmoisine/ton, fed from 42 to 54 weeks of age. Each treatment consisted of 10 replications with six hens. Dietary inclusion of paprika colorant improved (p < 0.05) the feed-conversion ratio and egg-production rate, while final body weight, weight change, feed intake, and egg weight and mass were not affected. The degrees of egg yolk and white were increased (p < 0.05) by the dietary supplements. Yolk color and shell thickness were enhanced (p < 0.05) by adding paprika and/or carmoisine colorants. Supplementation of the paprika colorant alone or in combination with carmoisine increased (p < 0.05) linolenic acid, oleic acid, and vitamin E concentrations in egg yolks. In contrast, egg yolk palmitic acid and liver malondialdehyde contents were decreased (p < 0.05). Paprika and carmoisine colorants and their combination improved (p < 0.05) blood lipid profile in treated hens. We concluded that the dietary supplementation of natural (paprika) colorants has an influential role in improving egg yolk color, production performance, and egg yolk fatty-acid profile in laying hens.

Metabolism of Carotenoids in Mammals

Pathways for xanthophyll metabolism have been proposed on the basis of several oxidation products of dietary xanthophylls detected in the tissues of fish, birds, and human subjects. No enzyme reaction had been characterized as responsible for the pathways until a mouse liver homogenate was found to oxidize the 3-hydroxy β-end of xanthophylls to a 3-oxo ε-end in the presence of a cofactor, NAD⁺. This oxidation consists of dehydrogenation to an unstable intermediate having a 3-oxo β-end group and the subsequent migration of a double bond. β,ε-Caroten-3'-one, a metabolite of β-cryptoxanthin, was found in human plasma, indicating that the same oxidative activity as that found in the mouse liver works in human tissues.The oxidative cleavage of carotenoids is mediated by two dioxygenases: a central cleavage enzyme and an asymmetric cleavage enzyme. In mice, the latter enzyme was suggested to eliminate carotenoids in tissues, while in humans, this enzyme is inactivated, resulting in carotenoid accumulation. In this chapter, carotenoid metabolism in mammals is described in terms of the oxidation of functional groups and cleavage of the carbon skeleton.

Triphenyltin exposure affects mating behaviors and attractiveness to females during mating in male guppies (Poecilia reticulata)

The impacts of triphenyltin (TPT) on ecological health have been of great concern due to their widespread use and ubiquity in aquatic ecosystems. However, little is known about the effects of TPT on the reproductive behaviors of fishes. Therefore, the present study was conducted to investigate the effects of TPT at environmentally relevant concentrations (0, 1 and 10 ng Sn/L) on the mating behaviors and the attractiveness to females during mating in male guppies (Poecilia reticulata). The results showed that TPT exposure disturbed the mating behaviors; the TPT-exposed male fish performed more sneaking attempts, but no changes in sigmoid courtship were displayed. The increases in sneaking attempts might be related to increases in testosterone levels induced by TPT exposure. In the context of a competing male, the TPT-exposed males were less attractive to females during mating. The decreases in attractiveness might be related to decreases in carotenoid-based coloration, shown as decreases in caudal fin redness values and skin carotenoid contents. In addition, TPT-induced total antioxidant capacities, the activities of superoxide dismutase and catalase, and the contents of malondialdehyde in liver and intestinal tissues indicated increases in oxidative stress. Both oxidative stress and coloration are linked to carotenoids. Thus, we speculated that the TPT-exposed males might use carotenoids to cope with increases in oxidative stress at the expense of carotenoid-based coloration. The disruption of mating behaviors and the decrease in attractiveness to females in male fish could result in reproductive failure. The present study underscores the importance of using behavioral tests as a sensitive tool in assessing the impact of pollutants present in aquatic environments.

Application of Paracoccus marcusii as a potential feed additive for laying hens

Carotenoids have been used for many years as an added pigment to enhance egg yolk color. One such carotenoid, astaxanthin, has a strong antioxidant activity and is produced by several microorganisms, including the bacterium Paracoccus marcusii, which has shown promise to be used as a feed additive. Therefore, this study investigated the use of P. marcusii as a possible source of pigmentation in layer hen feed to enhance egg yolk color. Paracoccus marcusii was fed to hens in a sucrose solution (10% m/v). The hens were fed daily and all eggs were collected for analysis. Dilutions of egg contents were plated onto selective media to detect the presence of known food pathogens (E. coli, Listeria, and Salmonella). In the feeding trial, there was no negative effect on hen body weight, egg production, or overall egg quality. There was a significant increase (P < 0.05) in yolk color as well as an increase in whole egg and yolk weight. There were also no known food pathogens detected in any of the egg samples. This study has shown promising results in using this bacterium as an effective feed additive for laying hens.

Effects of egg weight and in ovo injection of <i>α</i>-tocopherol on chick development, hatching performance, and lipid-soluble antioxidant concentrations in quail chick tissues

Abstract. Lipid-soluble antioxidants can be more effective for chick development when provided via in ovo (IO) injection than when supplemented to the maternal diet. This study was conducted to evaluate the effects of egg weight (EW) and IO injection of α-tocopherol on chick development, hatching performance and lipid-soluble antioxidant concentrations in residual yolk sac (RYS), liver and brain tissues of quail chicks. Eggs were obtained from quail breeders at days 72 and 128 of age and incubated at 37.8 ∘C and 60 % relative humidity. Each egg was numbered and weighed prior to incubation, and the average EW of all eggs was 11.76 ± 0.05 g. The eggs were divided into light (< 11.76 EW; EWL) and heavy (> 11.76 EW; EWH) groups (148 eggs per EW). Each EW group was divided into two IO groups: the control (non-injection) group and α-tocopherol group, in which 3.75 mg of α-tocopherol per egg was injected into the yolk sac followed by a 120 h incubation period. There were 64 eggs for each EW–IO treatment combination (16 eggs per EW per tray). The chick and RYS weights were significantly lower in the EWL group than in the EWH group. A significant EW by IO interaction suggested that IO increased the eggshell temperature of light quail eggs. The non-injected light eggs had a shorter hatching time due to the interaction of EW with IO. Hatchability, embryonic mortalities, and the cumulative hatching rate were not affected by EW or IO. The chick and middle toe lengths increased following IO administration (P < 0.05), which indicated that IO administration had positive effects on chick quality. However, shank length decreased following IO administration with an unchanged relative asymmetry (RA). IO significantly affected the absolute weights of the liver and heart and the relative weight of the heart, which was lower in the α-tocopherol group than in the control group. IO administration had no effect on total retinol and carotenoid concentrations in the RYS, liver and brain. Vitamin E, α-tocopherol and δ-tocopherol concentrations in the RYS, liver and brain were significantly higher in the α-tocopherol-treated chicks than in the control chicks. The highest brain α-tocopherol concentration was found in the α-tocopherol-treated chicks of the EWH group, indicating a significant interaction between EW and IO. The highest total lipid-soluble antioxidant concentrations were obtained following IO α-tocopherol treatment (P < 0.05), in the order brain < liver < RYS, but this pattern was not observed with δ-tocopherol. In conclusion, IO injection of α-tocopherol into the yolk sac affected the concentrations of tissue-specific lipid-soluble antioxidants in the RYS and tissues of newly hatched quail chicks, and EW had effects on various parameters.

Effects of Different Grain Sources in Both Maternal and Offspring Diets on Pigmentation and Growth Performance in Yellow-Skinned Chickens

This study aims at investigating the effects of different grain sources during pre-hatch (from diet of the breeders) and post-hatch (from the diet of broilers) on coloration (Roche color fan scores; L*, lightness; a*, redness; and b*, yellowness) as well as the growth performance in yellow-skinned chickens at market age (42 days old). In this experiment, six thousand yellow-skinned broiler breeders at 27 weeks were fed with a corn or sorghum and barley-based diet in which contained high (+) or low (-) xanthophyll levels, respectively. After the beginning of the trial, from day 41 to 42, eggs from two treatments were collected to artificial incubation. In this trial, 2×2 factorial designs were used and male chicks hatched from breeders fed with a corn or sorghum-based diet. According to the results, it demonstrated that hens fed with a corn-base diet were observed an elevated coloration both in the eggs and newly-hatched chicks (p<0.05). The dietary pigments improved pigment deposition in the egg yolk and the tissue of newly-hatched chicks. Besides, there was no difference in growth performance attributed to dietary grain sources both from hens or chicks. There showed no difference of coloration in abdominal fat, shank or breast skin (or kept at 4°C for 24 hours and 7 days) between two breeder grain sources (p>0.05). However, abdominal fat, shank and breast skin from the broiler chicks fed with the corn-based diet had a significantly higher RFC scores, a* and b* value than that fed with the sorghum and barley-based diet. The current results indicated that the broiler dietary grain sources (different xanthophyll contents), other than the breeder dietary grain sources influenced the pigmentation in abdominal fat, shank and breast skin, and the skins stored at 4°C in broiler. Therefore, it can be suggested that a low xanthophyll-containing diet (sorghum and barley-based diet) might be applied in yellow-skinned broiler breeders without causing negative effects of coloration or growth performance on their offspring at market age.

Disruptions in aromatase expression in the brain, reproductive behavior, and secondary sexual characteristics in male guppies (Poecilia reticulata) induced by tributyltin

Although bioaccumulation of tributyltin (TBT) in fish has been confirmed, information on possible effects of TBT on reproductive system of fish is still relatively scarce, particularly at environmentally relevant levels. To evaluate the adverse effects and intrinsic toxicological properties of TBT in male fish, we studied aromatase gene expression in the brain, sex steroid contents, primary and secondary sexual characteristics, and reproductive behavior in male guppies (Poecilia reticulata) exposed to tributyltin chloride at the nominal concentrations of 5, 50, and 500 ng/L for 28 days in a semi-static exposure system. Radioimmunoassay demonstrated that treatment with 50 ng/L TBT caused an increase in systemic levels of testosterone of male guppies. Gonopodial index, which showed a positive correlation with testosterone levels, was elevated in the 5 ng/L and 50 ng/L TBT treated groups. Real-time PCR revealed that TBT exposure had inhibiting effects on expression of two isoforms of guppy aromatase in the brain, and these changes at the molecular levels were associated with a disturbance of reproductive behavior of the individuals, as measured by decreases in frequencies of posturing, sigmoid display, and chase activities when males were paired with females. This study provides the first evidence that TBT can cause abnormalities of secondary sexual characteristics in teleosts and that suppression of reproductive behavior in teleosts by TBT is due to its endocrine-disrupting action as an aromatase inhibitor targeting the nervous system.

A 3-hydroxy β-end group in xanthophylls is preferentially oxidized to a 3-oxo ε-end group in mammals

We previously found that mice fed lutein accumulated its oxidative metabolites (3'-hydroxy-ε,ε-caroten-3-one and ε,ε-carotene-3,3'-dione) as major carotenoids, suggesting that mammals can convert xanthophylls to keto-carotenoids by the oxidation of hydroxyl groups. Here we elucidated the metabolic activities of mouse liver for several xanthophylls. When lutein was incubated with liver postmitochondrial fraction in the presence of NAD(+), (3'R,6'R)-3'-hydroxy-β,ε-caroten-3-one and (6RS,3'R,6'R)-3'-hydroxy-ε,ε-caroten-3-one were produced as major oxidation products. The former accumulated only at the early stage and was assumed to be an intermediate, followed by isomerization to the latter. The configuration at the C3' and C6' of the ε-end group in lutein was retained in the two oxidation products. These results indicate that the 3-hydroxy β-end group in lutein was preferentially oxidized to a 3-oxo ε-end group via a 3-oxo β-end group. Other xanthophylls such as β-cryptoxanthin and zeaxanthin, which have a 3-hydroxy β-end group, were also oxidized in the same manner as lutein. These keto-carotenoids, derived from dietary xanthophylls, were confirmed to be present in plasma of normal human subjects, and β,ε-caroten-3'-one was significantly increased by the ingestion of β-cryptoxanthin. Thus, humans as well as mice have oxidative activity to convert the 3-hydroxy β-end group of xanthophylls to a 3-oxo ε-end group.

Diversity, physiology, and evolution of avian plumage carotenoids and the role of carotenoid-protein interactions in plumage color appearance

The diversity of vibrant plumage colors in birds has evolved as a direct result of social and environmental pressures. To fully understand these underlying pressures it is necessary to elucidate the mechanisms for the creation of novel plumage colors which include the metabolic transformations of dietary carotenoids and spectral tuning of the molecules within the feather protein environment. Recent advances in this field have greatly expanded the number and breadth of avian species for which plumage pigmentation has been characterized, making it possible to reconstruct the phylogenetic history of carotenoid usage in plumage. Resonance Raman and classical Raman spectroscopic techniques have been employed with great effect in the study of carotenoids in situ. The application of these methods have two benefits: to identify carotenoids in feathers that are unavailable for destructive sampling; and to study the spectral tuning resulting from the interaction between the carotenoids and the proteins to which they are bound. This review presents a summary of recent advances in the understanding of the molecular factors controlling the coloration of avian carotenoid plumage obtained through the application of both bioanalytical and spectroscopic methodologies.

Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids

Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total ß-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, ß-carotene and β-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p<0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal.

Appearance traits in fish farming: progress from classical genetics to genomics, providing insight into current and potential genetic improvement

Appearance traits in fish, those external body characteristics that influence consumer acceptance at point of sale, have come to the forefront of commercial fish farming, as culture profitability is closely linked to management of these traits. Appearance traits comprise mainly body shape and skin pigmentation. Analysis of the genetic basis of these traits in different fish reveals significant genetic variation within populations, indicating potential for their genetic improvement. Work into ascertaining the minor or major genes underlying appearance traits for commercial fish is emerging, with substantial progress in model fish in terms of identifying genes that control body shape and skin colors. In this review, we describe research progress to date, especially with regard to commercial fish, and discuss genomic findings in model fish in order to better address the genetic basis of the traits. Given that appearance traits are important in commercial fish, the genomic information related to this issue promises to accelerate the selection process in coming years.

Absorption and metabolism of dietary carotenoids

A number of carotenoids with diverse structures are present in foods and have beneficial effects on human health due to their common antioxidant activity and their respective biological activities. The major carotenoids found in human tissues, however, are limited to several including such as β-carotene, lycopene, and lutein. We have little knowledge of whether carotenoids are selectively absorbed in intestine and metabolized discriminately in the body. Moreover, the metabolic transformation of carotenoids in mammals other than vitamin A formation has not been fully elucidated. Here, the intestinal absorption and oxidative metabolism of dietary carotenoids are reviewed with a focus on dietary xanthophylls.

Flesh color association with polymorphism of the tyrosinase gene in different Chinese chicken breeds

In order to study genetic variation of tyrosinase gene in four different flesh color chicken breeds selected from special districts including Guyuan, Wenchang, Tibetan and Hisex chicken, five loci of the TYR gene exon-1 and one locus of 5' flanking region were analyzed in PCR-SSCP and DNA sequencing. The results indicated that there were polymorphisms only at TYR1 and TYR3 locus. At TYR1 locus located in exon-1, there were three genotypes (TT, CC, TC), respectively, in three Chinese chicken breeds, and Genotype CC had not been detected in Hisex chicken. At TYR3 locus located in 5' flanking region, there were three genotypes (GG, AA and GA) in Chinese local chicken breeds and genotype AA had not been detected in Hisex chicken breed. It was concluded that there were many variations of TYR gene in Chinese local chicken breeds. DNA sequencing of PCR products for different genotypes showed that there were two mutation sites, respectively, C to T at TYR1 locus and G to A at TYR3 locus. Mutation at TYR1 locus did not cause any amino acid variation. The chi-square analysis revealed that there were significant statistical differences generally between flesh color and the two loci among four chicken populations (P < 0.01). Our results suggested that the flesh color was related to genotype of TYR gene in Chinese chicken breeds. This study provided original information for elucidating the possible roles of exon-1 of TYR gene and 5' flanking region in chickens with different flesh color chicken.

Viability of brown trout embryos positively linked to melanin-based but negatively to carotenoid-based colours of their fathers

‘Good-genes’ models of sexual selection predict significant additive genetic variation for fitness-correlated traits within populations to be revealed by phenotypic traits. To test this prediction, we sampled brown trout (Salmo trutta) from their natural spawning place, analysed their carotenoid-based red and melanin-based dark skin colours and tested whether these colours can be used to predict offspring viability. We produced half-sib families by in vitro fertilization, reared the resulting embryos under standardized conditions, released the hatchlings into a streamlet and identified the surviving juveniles 20 months later with microsatellite markers. Embryo viability was revealed by the sires' dark pigmentation: darker males sired more viable offspring. However, the sires' red coloration correlated negatively with embryo survival. Our study demonstrates that genetic variation for fitness-correlated traits is revealed by male colour traits in our study population, but contrary to predictions from other studies, intense red colours do not signal good genes.

Effects of maternal dietary supplementation with three sources of carotenoids on the retinyl esters of egg yolk and developing quail liver

The effects of supplementation of the maternal diet of quail with three natural sources of carotenoids (alfalfa nutrient concentrate (PX agrotrade mark), tomato powder and marigold extract) on the accumulation of retinol and retinyl esters in egg yolk and in the liver of the new hatchling and maternal were investigated. The present study showed that the vitamin A in quail egg yolk was present in 4 different forms, namely retinol (R 52-62%), retinyl linoleate (RL 9-11%), retinyl stearate (RS 4%), retinyl oleate (RO 11-15%) and retinyl palmitate (RP 13-22%). The retinyl ester profile of the liver of newly hatched quail (R 2-4%, RL 8-12%, RS 19-21%, RO 12-15%, RP 50-55%) differs from that of egg yolk but was similar to that of the liver of adult quail (R 1%, RL 5-6%, RS 21-28%, RO 9-12%, RP 54-63%). It has been shown that RO and RP concentrations in egg yolk and the liver of day old quail chick significantly increased as a result of carotenoid supplementation of the maternal diet.

Individual colour patches as multicomponent signals

Colour patches are complex traits, the components of which may evolve independently through a variety of mechanisms. Although usually treated as simple, two-dimensional characters and classified as either structural or pigmentary, in reality colour patches are complicated, three-dimensional structures that often contain multiple pigment types and structural features. The basic dermal chromatophore unit of fishes, reptiles and amphibians consists of three contiguous cell layers. Xanthophores and erythrophores in the outermost layer contain carotenoid and pteridine pigments that absorb short-wave light; iridophores in the middle layer contain crystalline platelets that reflect light back through the xanthophores; and melanophores in the basal layer contain melanins that absorb light across the spectrum. Changes in any one component of a chromatophore unit can drastically alter the reflectance spectrum produced, and for any given adaptive outcome (e.g. an increase in visibility), there may be multiple biochemical or cellular routes that evolution could take, allowing for divergent responses by different populations or species to similar selection regimes. All of the mechanisms of signal evolution that previously have been applied to single ornaments (including whole colour patches) could potentially be applied to the individual components of colour patches. To reach a complete understanding of colour patch evolution, however, it may be necessary to take an explicitly multi-trait approach. Here, we review multiple trait evolution theory and the basic mechanisms of colour production in fishes, reptiles and amphibians, and use a combination of computer simulations and empirical examples to show how multiple trait evolution theory can be applied to the components of single colour patches. This integrative perspective on animal colouration opens up a host of new questions and hypotheses. We offer specific, testable functional hypotheses for the most common pigmentary (carotenoid, pteridine and melanin) and structural components of vertebrate colour patches.

Carotenoid Pigments in Male House Finch Plumage in Relation to Age, Subspecies, and Ornamental Coloration

Like males of many bird species, male House Finches (Carpodacus mexicanus) have patches of feathers with ornamental coloration that are due to carotenoid pigments. Within populations, male House Finches vary in expression of ornamental coloration from pale yellow to bright red, which previous research suggested was the result of variation in types and amounts of carotenoid pigments deposited in feathers. Here we used improved analytical techniques to describe types and amounts of carotenoid pigments present in that plumage. We then used those data to make comparisons of carotenoid composition of feathers of male House Finches at three levels: among individual males with different plumage hue and saturation, between age groups of males from the same population, and between males from two subspecies that differ in extent of ventral carotenoid pigmentation (patch size): large-patched C. m. frontalis from coastal California and small-patched C. m. griscomi from Guerrero, Mexico. In all age groups and populations, the ornamental plumage coloration of male House Finches resulted from the same 13 carotenoid pigments, with 3-hydroxy echinenone and lutein being the most abundant carotenoid pigments. The composition of carotenoids in feathers suggested that House Finches are capable of metabolic transformation of dietary forms of carotenoids. The hue of male plumage depended on component carotenoids, their relative concentrations, and total concentration of all carotenoids. Most 4-keto (red) carotenoids were positively correlated with plumage redness, and most yellow carotenoid pigments were negatively associated with plumage redness, although the strength of the relationship for specific carotenoid pigments varied among age groups and subspecies. Using age and subspecies as factors and concentration of each component carotenoid as dependent variables in a MANOVA, we found a distinctive pigment profile for each age group within each subspecies. Among frontalis males, hatch-year birds did not differ from adults in mean plumage hue, but they had a significantly lower proportion of red pigments in their plumage, and significantly lower levels of the red piments adonirubin and astaxanthin, but significantly higher levels of the yellow pigment zeaxanthin, than adult males. Among griscomi males, hatch-year birds differed from adults in plumage hue but not significantly in pigment composition, though in general their feathers had lower concentrations of red pigments and higher concentrations of yellow pigments than adult males. Both adult and hatch-year frontalis males differed from griscomi males in having significantly higher levels of most yellow carotenoid pigments and significantly lower levels of most red carotenoid pigments. Variation in pigment profiles of subspecies and age classes may reflect differences among the groups in carotenoid metabolism, in dietary access to carotenoids, or in exposure to environmental factors, such as parasites, that may affect pigmentation.

Fatty acid, carotenoid and vitamin A composition of tissues of free living gulls

The aim of this study was to investigate fatty acid and carotenoid profile as well as vitamin A (retinol and retinol esters) content in gull (Larus fucus) tissues. Palmitic (16:0) and stearic (18:0) fatty acids were major saturates in all the tissues studied. Oleic acid (18:1n-9) was the major monounsaturate in the tissue phospholipids varying from 11.9% (liver) up to 18.2% (lung). Arachidonic acid (20:4n-6) was the major unsaturate in the phospholipid fraction in all the tissues. Liver contained the highest total carotenoid concentration which was 5 and 7 fold higher compared to kidney and pancreas. In the liver beta-carotene was major carotenoid. In contrast, in all other tissues beta-carotene was minor fraction with lutein being major carotenoid. Zeaxanthin, canthaxanthin, beta-cryptoxanthin and echinenone were also identified in the gull tissues. Liver and kidney were characterised by the highest vitamin A concentrations (1067.5 and 867.5 microg/g, respectively). Retinol comprised from 55.3% (pancreas) down to 8% (kidney) of the total vitamin A but was not detected in the abdominal fat. Retinyl palmitate was the major retinyl ester in the liver, kidney and heart (44.2; 38.1 and 46.0% of total retinyl esters). In muscles and abdominal fat retinyl stearate was the major retinyl ester fraction. Therefore high proportions of beta-carotene were found in gull liver and peripheral tissues were enriched by lutein and zeaxanthin compared to the liver, a very high concentration of retinyl esters in the kidney was observed and tissue-specificity in retinyl ester proportions in peripheral tissues was found.