Variation In Coloration Research Articles

Performance of visual vs. software-assisted photo-identification in mark-recapture studies: a case study examining different life stages of the Pacific Horned Frog (Ceratophrys stolzmanni)

Abstract The use of individual phenotypic features as non-invasive marks through photo-identification (photo-ID) has many advantages for individual-based field studies. However, since error rates vary between species, matching techniques, and image qualities, it is important to assess error rates to evaluate the reliability of photo-ID. We tested the performance of this method in the Pacific Horned Frog, Ceratophrys stolzmanni, a threatened anuran with a variable dorsal coloration. We compared the effectiveness of visual (i.e. human recognition) versus software-assisted recognition techniques (Wild-ID and APHIS), and assessed the potential applicability of these techniques to identify post-metamorphic individuals (froglets). The three techniques differed in their performance. The visual technique was the only one to produce type I errors between pairs of images (i.e. matching images which are not true matching pairs), however it also produced fewer type II errors (i.e. not identifying true matching pairs of images) than the software-assisted techniques. For froglets, we found that similarity scores calculated by photo-ID software did not differ significantly between groups of froglets and older individuals, supporting the idea that colour patterns in this species remain stable after metamorphosis. The lack of type I errors and the substantial reduction in required time achieved through the use of software, make software-assisted techniques (particularly Wild-ID) a valid and convenient matching technique for C. stolzmanni. We propose that photo-ID can also be applied to froglets of this species, since the pattern at this stage appears to be as variable as in adults and maintained through life.

Male preference for conspecific females depends on male size in the splendid darter, Etheostoma barrenense

Mating preferences vary among individuals in response to a number of factors, such as the age and phenotype of the choosing individual. However, studies addressing variation in mating preferences generally focus on female preferences and usually are limited to choice within a species. Variation in preferences likely also exists at the species boundary, affecting an individual’s propensity to mate with heterospecific individuals. In darters (Percidae: Etheostoma), male mating preferences are thought to prevent interbreeding between species, with male preferences for conspecifics sometimes as strong as, or stronger than, females’. In the current study, we tested whether male size and coloration predicts preference for conspecific females in Etheostoma barrenense. Previous studies have shown that males of this species strongly prefer conspecific females relative to females of the sympatric congener, the banded darter, Etheostoma zonale; however, those studies did not consider whether variation in male size or coloration affected preferences. Comparing large and small males of E. barrenense in dichotomous choice assays, we found that larger males exhibited stronger preferences for conspecific females and had proportionally more red coloration than smaller males. The proportion of red coloration did not significantly predict male preferences, suggesting that male size rather than male coloration predicts variation in male mating preferences for conspecific females in E. barrenense. Male size is often considered an indicator of individual quality. Alternatively, size might better reflect age in the focal species, suggesting that experience and learning may shape male preferences for conspecific females.

Canaries changing colors

Sexual Dimorphism Many animals are sexually dimorphic, with different phenotypes in males and females. To identify the genetic basis of sexual differences in bird coloration, Gazda et al. investigated red coloration in mosaic canaries and related species (see the Perspective by Chen). Using a combination of genetic crosses, genomic mapping, transcriptomics, and comparative analyses, the authors show that trans-regulation of the carotenoid-processing gene BCO2 is involved in sexual dichromatism. Although such variation in coloration among the sexes is common, particularly in birds, there are few candidate genes known to be involved. This study helps to elucidate the molecular mechanisms that underlie the evolution of dichromatism and may aid in uncovering sexually selected traits. Science , this issue p. [1270][1]; see also p. [1185][2] [1]: /lookup/doi/10.1126/science.aba0803 [2]: /lookup/doi/10.1126/science.abc2242

A genetic mechanism for sexual dichromatism in birds.

Sexual dichromatism, a difference in coloration between males and females, may be due to sexual selection for ornamentation and mate choice. Here, we show that carotenoid-based dichromatism in mosaic canaries, a hybrid phenotype that arises in offspring of the sexually dichromatic red siskin and monochromatic canaries, is controlled by the gene that encodes the carotenoid-cleaving enzyme β-carotene oxygenase 2 (BCO2). Dichromatism in mosaic canaries is explained by differential carotenoid degradation in the integument, rather than sex-specific variation in physiological functions such as pigment uptake or transport. Transcriptome analyses suggest that carotenoid degradation in the integument might be a common mechanism contributing to sexual dichromatism across finches. These results suggest that differences in ornamental coloration between sexes can evolve through simple molecular mechanisms controlled by genes of major effect.

Plumage coloration and morphometrics of the Little Owl Athene noctua in the Western Palearctic

The Little Owl is a species with a wide range in the Palearctic. Thirteen subspecies have been described based on small coloration or size differences. Recently, genetic studies in the western portion of the European range have shown the presence of some well distinct clades. We examined the variation in structural size and coloration of Western Palearctic birds, with particular attention to the pattern of light and dark pigmentation on the tail, and we checked for the presence of UV reflection through reflectance spectroscopy. We did not find clear-cut differences in size or plumage between the currently accepted subspecies, nor between individuals pertaining to the different genetic clade areas. There is a trend for individuals from the western genetic clade (Iberia, France, England and central Europe) to have longer tarsus with smaller wings, while individuals from the eastern generic clade (Balkans) have an opposite pattern. Italian birds are intermediate. The tail of Balkan birds has a wider dark pigmentation, with reduced light spots. Little owl feathers do not show reflectance in the UV part of the spectrum. We found a very large variation of morphological and color patterns between individuals collected in the same geographical area. Currently, the arrangement of individuals to any Little owls' subspecies on morphological data appears to be a very difficult task.

Being red, blue and green: the genetic basis of coloration differences in the strawberry poison frog (Oophaga pumilio)

BackgroundAnimal coloration is usually an adaptive attribute, under strong local selection pressures and often diversified among species or populations. The strawberry poison frog (Oophaga pumilio) shows an impressive array of color morphs across its distribution in Central America. Here we quantify gene expression and genetic variation to identify candidate genes involved in generating divergence in coloration between populations of red, green and blue O. pumilio from the Bocas del Toro archipelago in Panama.ResultsWe generated a high quality non-redundant reference transcriptome by mapping the products of genome-guided and de novo transcriptome assemblies onto a re-scaffolded draft genome of O. pumilio. We then measured gene expression in individuals of the three color phenotypes and identified color-associated candidate genes by comparing differential expression results against a list of a priori gene sets for five different functional categories of coloration – pteridine synthesis, carotenoid synthesis, melanin synthesis, iridophore pathways (structural coloration), and chromatophore development. We found 68 candidate coloration loci with significant expression differences among the color phenotypes. Notable upregulated examples include pteridine synthesis genes spr, xdh and pts (in red and green frogs); carotenoid metabolism genes bco2 (in blue frogs), scarb1 (in red frogs), and guanine metabolism gene psat1 (in blue frogs). We detected significantly higher expression of the pteridine synthesis gene set in red and green frogs versus blue frogs. In addition to gene expression differences, we identified 370 outlier SNPs on 162 annotated genes showing signatures of diversifying selection, including eight pigmentation-associated genes.ConclusionsGene expression in the skin of the three populations of frogs with differing coloration is highly divergent. The strong signal of differential expression in pteridine genes is consistent with a major role of these genes in generating the coloration differences among the three morphs. However, the finding of differentially expressed genes across pathways and functional categories suggests that multiple mechanisms are responsible for the coloration differences, likely involving both pigmentary and structural coloration. In addition to regulatory differences, we found potential evidence of differential selection acting at the protein sequence level in several color-associated loci, which could contribute to the color polymorphism.

Red Coloration in an Anchialine Shrimp: Carotenoids, Genetic Variation, and Candidate Genes.

Red coloration is a widely distributed phenotype among animals, yet the pigmentary and genetic bases for this phenotype have been described in relatively few taxa. Here we show that the Hawaiian endemic anchialine shrimp Halocaridina rubra is red because of the accumulation of astaxanthin. Laboratory colonies of phylogenetically distinct lineages of H. rubra have colony-specific amounts of astaxanthin that are developmentally, and likely genetically, fixed. Carotenoid supplementation and restriction experiments failed to change astaxanthin content from the within-colony baseline levels, suggesting that dietary limitation is not a major factor driving coloration differences. A possible candidate gene product predicted to be responsible for the production of astaxanthin in H. rubra and other crustaceans is closely related to the bifunctional cytochrome P450 family 3 enzyme CrtS found in fungi. However, homologs to the enzyme thought to catalyze ketolation reactions in birds and turtles, CYP2J19, were not found. This work is one of the first steps in linking phenotypic variation in red coloration of H. rubra to genotypic variation. Future work should focus on (1) pinpointing the genes that function in the bioconversion of dietary carotenoids to astaxanthin, (2) examining what genomic variants might drive variation in coloration among discrete lineages, and (3) testing more explicitly for condition-dependent carotenoid coloration in crustaceans.

Text Region Extraction From Scene Images Using AGF and MSER

The natural scene images contain text as an integral part of that image that supplies paramount knowledge about it. This information and knowledge can be used in the variety of purposes like image-based searching, automatic number plate recognition, robot navigation, etc. but text region extraction and detection in scenery images could be quite a challenging job due to image blur, distortion, noise, etc. In this paper, we discuss a method for extraction of text regions by generating prospective components by applying maximally stable extremal regions (MSER) and boundary smoothing by Alternating guided image filter, which is one of the newest filters to deal with noise and halo effect elimination. The separation of non-text & text components is achieved by AdaBoost classifier that separates text and non-text on the basis of the three text specific features namely maximum stroke width ratio, compactness, color divergence. The proposed method assist in extracting text regions from the blurred and low contrast natural scene images effectively. The ICDAR 2013 training and testing dataset is applied for the experiments and evaluation of the method. The evaluation is carried out using deteval software for calculating precision, f-measure, recall for the detected, and extracted text regions.

Variable colour patterns indicate multidimensional, intraspecific trait variation and ecological generalization in moths

Animal colour patterns long have provided information about key processes that drive the ecological and evolutionary dynamics of biological diversity. Theory and empirical evidence indicate that variation in colour patterns and other traits among individuals generally improves the performance of populations and species, for example by reducing predation risk, increasing establishment success, improving resilience to environmental change, and decreasing risk of extinction. However, little is known about whether and how variation in colour pattern among species is associated with variation in other phenotypic dimensions. To address this issue, we analysed associations of colour pattern with morphological, behavioural and life‐history traits on the basis of data for nearly 400 species of noctuid moths. We found that moths with more variable colour patterns had longer flight activity periods, more diverse habitats and a greater number of host plant species than species with less variable colour patterns. Variable coloration in adult noctuid moths therefore can be considered as indicative of broader niches and generalist diets. Colour pattern variability was not significantly associated with overwintering stage or body size (wing span), and it was independent of whether the colour pattern of the larvae was non‐variable, variable or highly variable. Colour pattern variation during the larval stage tended to increase as the duration of the flight activity period increased, but was independent of the length of the larval period, diet breadth and habitat use. The realization that information on colour pattern variation in adult moths, and possibly other organisms, offers a proxy for niche breadth and dietary generalization can inform management and conservation biology.

Morphological study of larval development and the transition to juvenile stage in thin-lipped mullet, Liza ramada

Introduction: The detailed description of larval and juvenile stages of L. ramada is so far lacking.Aim of the Work: The present study aimed to describe larval development and the morphological transition to the juvenile stage in L. ramada after artificial spawning.Material and Methods: In this study, we described early development of Liza ramada over the early rearing period of 63 days post-hatching.Results: The newly hatched larvae have closed mouth and anus. At seven days post-hatching, the larvae have opened mouth and both yolk sac and oil globules disappeared. At 14 days, larvae have a distinct fins and increased skin pigmentation. At 21 days post-hatching, the larvae have variable coloration with more density. At 28 days post-hatching, the body depth of larvae increased and the stomach contains some food indicating the larval ability to digest external food. In 35 days-old larvae, the eyes become fully pigmented. At 42 days post-hatching, the larvae have high density of pigmentation all over the body and transparent caudal fin with rays. At 49 days post-hatching, the body of juvenile is distinctly elongated and laterally compressed with obvious scales. By 56 days post-hatching, the fish is covered with scales and well-developed rays. At 63 days post-hatching, the body becomes large and completely covered with scales and high density of pigmentation. The larvae begin transformation to juvenile stage at 42 days post-hatching and then finished the transformation at 63 days post-hatching. Importantly, the juvenile stage of L. ramada can be handled safely at 63 days post-hatching.Conclusion: The juvenile’s production of L. ramada requires a period of 63.

Anatomy and shell shape variability in a land snail Bostryx torallyi (Stylommatophora: Bulimulidae)

Introduction: The gastropod Bostryx torallyi shows high variability in shell shape and coloration. Subspecies of this organism have been described based on shell characters but, since they were slightly different, they were synonymized afterwards. Until now, shell variability has been analyzed only descriptively and its anatomy is still unknown. Objective: In this study, I provide anatomical information of B. torallyi and apply a geometric morphometric analysis to evaluate the shell shape variation among specimens. Methods: To accomplish this, type material and numerous lots were examined and dissected out. Additionally, relative warp analysis, based on 9 landmarks in ventral view of the shell, was performed using 80 specimens of 9 localities from Bolivia and Argentina. Results: According to our results, geometric morphometrics is a suitable method to evaluate differences in shell shape among localities; for instance, distinctions in the shell were noticeable between gastropods of low and high altitudes. On the other hand, it was established that the coloration of this species is independent of large-scale factors since the examined specimens came from environments with similar conditions. Furthermore, the sculpture of the protoconch and anatomy of B. torallyi coincided with the other Argentinian species of the genus. Conclusions: Therefore, I concluded that a geometric morphometric analysis of shell shape is a good complement to traditional qualitative description of the characteristics of the shell in this species.

Color characteristics, pigment accumulation and biosynthetic analyses of leaf color variation in herbaceous peony (Paeonia lactiflora Pall.).

Herbaceous peony (Paeonia lactiflora Pall.) is one of the color-leaved ornamental spring plants, with graceful appearance and splendid color. However, the underlying mechanism of this coloration variation from purple to green has not been studied in P. lactiflora. In th study, the leaves in purple, purple-green, and green stages were compared in terms of anatomical, physiological, and molecular. We found that the variation of leaf color from purple to green was mainly determined by the change in pigments distributed in the leaf surface. Physiological experiments showed a significant increase in chlorophyll contents and a notable reduction in anthocyanin contents in leaves from the purple to green stages. We further found that the anthocyanin biosynthesis-related dihydroflavonol 4-reductase (DFR) gene and anthocyanin synthase (ANS) gene as well as chlorophyll biosynthesis-related glutamyl-tRNA reductase (HEMA) gene showed a decreased trend in leaves from purple to green stages, whereas the chlorophyll degradation-related chlorophyll b reductase (NYC) gene showed a rising trend. Alteration of DFR and ANS gene expression might reduce anthocyanin accumulation, whereas increased HEMA gene expression would enhance chlorophyll biosynthesis and reduced NYC gene expression would inhibit chlorophyll degradation. Consequently, reduction in anthocyanins and enhanced deposition of chlorophylls resulted in leaf coloration variation from purple to green in P. lactiflora, which could improve our understanding of its mechanism for further studies.

Reduction of nitrate and nitrite in Iberian dry cured loins and its effects during drying process

Four batches of Iberian dry-cured loins were manufactured with reduced ingoing amounts of both nitrate and nitrite: 150 mg/kg, 75 mg/kg, 37.5 mg/kg and 0 mg/kg. The effect of reducing or removing nitrate and nitrite and time of drying on physicochemical parameters (moisture, pH, water activity, chloride and residual nitrate and nitrite contents), instrumental colour and nitrosylmyoglobin content, lipid and protein oxidation and on microbiological counts (L. monocytogenes, aerobic mesophilic bacteria and moulds and yeast counts) were investigated. Lipid oxidation increased during the drying process being higher for non-added NO3−/NO2−, meanwhile protein oxidation affected also those with 37.5 and 75 mg/kg of NO3−/NO2− added. The removal of these additives affected instrumental colour coordinates and total colour changes showing that the variation of coloration would be perceptible by the consumer. Nitrosylmyoglobin content was significantly higher for NO3−/NO2− added loins. Reduced levels of these additives up to 37.5 mg/kg did not show significant effects on their physico-chemical, microbiological and colour.

Analyses of plumage coloration and genetic variation confirm the hybridization of Pipra fasciicauda and Pipra aureola in the Brazilian Amazon basin

The present study aimed to confirm the occurrence of a hybridization event between the band-tailed manakin (Pipra fasciicauda) and the crimson-hooded manakin (Pipra aureola), based on the existence of a specimen that presents morphological traits of both taxa. We analyzed 297 taxidermized skins of adult males of the two species, including the potential hybrid. We also analyzed the mitochondrial (ND2, ND3 e COI) and nuclear (FGB-I5, MB-I2 e GAPDH-I3) genes of 12 adult specimens of the two taxa, diagnosed phenotypically, in addition to the potential hybrid. The analyses of the plumage indicated that the potential hybrid has an intermediate pattern of white banding on the tail that is less extensive than that found in Pipra fasciicauda, but that its other phenotypic traits are characteristic of Pipra aureola. The molecular topologies revealed two clades, one that groups P. aureola together with the potential hybrid, and the other that corresponds to P. fasciicauda. These findings allowed us to confirm the occurrence of a process of hybridization and potential introgression through secondary events in the P. aureola lineage.

Disentangling Population History and Character Evolution among Hybridizing Lineages.

Understanding the origin and maintenance of adaptive phenotypic novelty is a central goal of evolutionary biology. However, both hybridization and incomplete lineage sorting can lead to genealogical discordance between the regions of the genome underlying adaptive traits and the remainder of the genome, decoupling inferences about character evolution from population history. Here, to disentangle these effects, we investigated the evolutionary origins and maintenance of Batesian mimicry between North American admiral butterflies (Limenitis arthemis) and their chemically defended model (Battus philenor) using a combination of de novo genome sequencing, whole-genome resequencing, and statistical introgression mapping. Our results suggest that balancing selection, arising from geographic variation in the presence or absence of the unpalatable model, has maintained two deeply divergent color patterning haplotypes that have been repeatedly sieved among distinct mimetic and nonmimetic lineages of Limenitis via introgressive hybridization.

Signal evolution and morphological complexity in hummingbirds (Aves: Trochilidae).

Understanding how animal signals are produced is critical for understanding their evolution because complexity and modularity in the underlying morphology can affect evolutionary patterns. Hummingbird feathers show some of the brightest and most iridescent colors in nature. These are produced by optically complex stacks of hollow, platelet-shaped organelles called melanosomes. Neither how these morphologies produce colors nor their evolution has been systematically studied. We first used nanoscale morphological measurements and optical modeling to identify the physical basis of color production in 34 hummingbird species. We found that, in general, the melanosome stacks function as multilayer reflectors, with platelet thickness and air space size explaining variation in hue (color) and saturation (color purity). Additionally, light rays reflected from the outer keratin surface interact with those reflected by small, superficial melanosomes to cause secondary reflectance peaks, primarily in short (blue) wavelengths. We then compared variation of both the morphological components and the colors they produce. The outer keratin cortex evolves independently and is more variable than other morphological traits, possibly due to functional constraints on melanosome packing. Intriguingly, shorter wavelength colors evolve faster than longer wavelength colors, perhaps due to developmental processes that enables greater lability of the shapes of small melanosomes. Together, these data indicate that increased structural complexity of feather tissues is associated with greater variation in morphology and iridescent coloration.

Male characteristics as predictors of genital color and display variation in vervet monkeys

In the animal kingdom, conspicuous colors are often used for inter- and intra-sexual communication. Even though primates are the most colorful mammalian taxon, many questions, including what potential information color signals communicate to social partners, are not fully understood. Vervet monkeys (Chlorocebus pygerythrus) are ideal to examine the covariates of color signals. Males have multi-colored genitals, which they present during distinctive male-male interactions, known as the “Red-White-and-Blue” (RWB) display, but the genitals are also visible across a variety of other contexts, and it is unclear what this color display signals to recipients. We recorded genital color presentations and standardized digital photos of male genitals (N = 405 photos) over one mating season for 20 adult males in three groups at the Samara Private Game Reserve, South Africa. We combined these with data on male characteristics (dominance, age, tenure length, injuries, and fecal glucocorticoid metabolite concentrations). Using visual modeling methods, we measured single colors (red, white, blue) but also the contrasts between colors. We assessed the frequency of the RWB genital display and male variation in genital coloration and linked this to male characteristics. Our data suggest that the number of genital displays increased with male dominance. However, none of the variables investigated explained the inter- and intra-individual variation in male genital coloration. These results suggest that the frequency of the RWB genital display, but not its color value, is related to dominance, providing valuable insights on covariation in color signals and their display in primates.Significance statementConspicuous colors in animals often communicate individual quality to mates and rivals. By investigating vervet monkeys, a primate species in which males present their colorful genitals within several behavioral displays, we aim to identify the covariates of such colorful signals and their behavioral display. Using visual modeling methods for the color analysis and combining behavioral display data and color data with male characteristics, we found that high-ranking males displayed their colorful genitals more frequently than lower-ranking ones. In contrast, color variation was not influenced by male dominance, age, tenure length, or health. Our results can serve as a basis for future investigations on the function of colorful signals and behavioral displays, such as a badge of status or mate choice in primates.

Variable plastron coloration of the eastern painted turtles Chrysemys picta picta in a single locality of south-eastern Massachusetts, USA

Variable plastron coloration of the eastern painted turtles Chrysemys picta picta in a single locality of south-eastern Massachusetts, USA

Redness Variation in the Eurasian Scops-Owl Otus scops is Due to Pheomelanin But is Not Associated with Variation in the Melanocortin-1 Receptor Gene (MC1R)

Melanin-based colorations in birds constitute a paradigm for the study of the molecular basis of phenotypic variation. Variation in the melanocortin-1 receptor (MCR1) gene, a key regulator of melanin synthesis in feather melanocytes, can lead to changes in the production of melanin and hence in feather colour. Here we investigate the proximate mechanisms behind colour plumage polymorphism in the Eurasian Scops-owl Otus scops, a species showing pronounced variation in the degree of redness. Although eumelanin pigment was three times more abundant than pheomelanin pigments, the degree of plumage redness was more strongly associated with the amount of pheomelanin than eumelanin pigments. We detected only one synonymous substitution and one non-synonymous substitution in MC1R which were, however, not associated with variation in plumage coloration. Redness variation in Eurasian Scops-Owls is primarily due to variation in pheomelanin, and to genes or regulatory elements other than MCR1. —Aviles, J.M., Cruz-Miralles, A., Ducrest, A.-L., Simon, C., Roulin, A., Wakamatsu, K. & Parejo, D. (2020). Redness variation in the Eurasian Scops-owl Otus scops is due to pheomelanin but is not associated with variation in the melanocortin-1 receptor gene (mc1r). Ardeola, 67: 3-13.

Appearance before performance? Nutritional constraints on life-history traits, but not warning signal expression in aposematic moths.

Trade‐offs have been shown to play an important role in the divergence of mating strategies and sexual ornamentation, but their importance in explaining warning signal diversity has received less attention. In aposematic organisms, allocation costs of producing the conspicuous warning signal pigmentation under nutritional stress could potentially trade‐off with life‐history traits and maintain variation in warning coloration.We studied this with an aposematic herbivore Arctia plantaginis (Arctiidae), whose larvae and adults show extensive variation in aposematic coloration. In larvae, less melanic coloration (i.e. larger orange patterns) produces a more efficient warning signal against predators, whereas high amounts of melanism (smaller orange pattern) enhance thermoregulation, correlate with better immunity and make individuals harder to detect for naïve predators.We conducted a factorial rearing experiment with larvae originating from lines selected for either small or large orange signal size, which were reared on an artificial diet that had either low or high protein content. Protein content of the diet is critical for melanin production. We measured the effects of diet on individual coloration, life‐history traits, immune defence and reproductive output. We also compared the responses to dietary conditions between the small and large larval signal genotypes.Protein content of the diet did not affect warning coloration in the larval stage, but larval signal sizes differed significantly among selection lines, confirming that its variation is mainly genetically determined. In adults, signal line or diet did not affect coloration in hindwings, but males' forewings had more melanin on the high than on low protein diet. Contrary to coloration, diet quality had a stronger impact on life‐history traits: individuals developed for longer had smaller hindwing sizes in females and lower immune defence on the low protein content diet compared with the high. These costs were higher for more melanic larval signal genotypes in terms of development time and female hindwing size.We conclude that low plasticity in warning signal characteristics makes signal expression robust under varying dietary conditions. Therefore, variation in diet quality is not likely to constrain signal expression, but can have a bigger impact on performance.