Mutations in SLC45A2 lead to loss of melanin in parrot feathers

Bird plumage coloration is a complex and multifactorial process that involves both genetic and environmental factors. Diverse pigment groups contribute to plumage variation in different birds. In parrots, the predominant green color results from the combination of 2 different primary colors: yellow and blue. Psittacofulvin, a pigment uniquely found in parrots, is responsible for the yellow coloration, while blue is suggested to be the result of light scattering by feather nanostructures and melanin granules. So far, genetic control of melanin-mediated blue coloration has been elusive. In this study, we demonstrated that feather from the yellow mutant rose-ringed parakeet displays loss of melanosome granules in spongy layer of feather barb. Using whole genome sequencing, we found that mutation in SLC45A2, an important solute carrier protein in melanin synthetic pathway, is responsible for the sex-linked yellow phenotype in rose-ringed parakeet. Intriguingly, one of the mutations, P53L found in yellow Psittacula krameri is already reported as P58A/S in the human albinism database, known to be associated with human OCA4. We further showed that mutations in SLC45A2 gene affect melanin production also in other members of Psittaculidae family such as alexandrine and plum-headed parakeets. Additionally, we demonstrate that the mutations associated with the sex-linked yellow phenotype, localized within the transmembrane domains of the SLC45A2 protein, affect the protein localization pattern. This is the first evidence of plumage color variation involving SLC45A2 in parrots and confirmation of associated mutations in the transmembrane domains of the protein that affects its localization.

Utility of Feathers for Avian Influenza Virus Detection in Commercial Poultry

The present study evaluated the potential utility of feather samples for the convenient and accurate detection of avian influenza virus (AIV) in commercial poultry. Feather samples were obtained from AIV-negative commercial layer facilities in Iowa, USA. The feathers were spiked with various concentrations (106 to 100) of a low pathogenic strain of H5N2 AIV using a nebulizing device and were evaluated for the detection of viral RNA using a real-time RT-PCR assay immediately or after incubation at -20, 4, 22, or 37 °C for 24, 48, or 72 h. Likewise, cell culture medium samples with and without the virus were prepared and used for comparison. In the spiked feathers, the PCR reliably (i.e., 100% probability of detection) detected AIV RNA in eluates from samples sprayed with 103 EID50/mL or more of the virus. Based on half-life estimates, the feathers performed better than the corresponding media samples (p < 0.05), particularly when the samples were stored at 22 or 37 °C. In conclusion, feather samples can be routinely collected from a poultry barn as a non-invasive alternative to blood or oropharyngeal-cloacal swab samples for monitoring AIV.

The feather epithelium contributes to the dissemination and ecology of clade 2.3.4.4b H5 high pathogenicity avian influenza viruses in ducks

Immature feathers are known replication sites for high pathogenicity avian influenza viruses (HPAIVs) in poultry. However, it is unclear whether feathers play an active role in viral transmission. This study aims to investigate the contribution of the feather epithelium to the dissemination of clade 2.3.4.4b goose/Guangdong/1996 lineage H5 HPAIVs in the environment, based on natural and experimental infections of domestic mule and Muscovy ducks. During the 2016-2022 outbreaks, H5 HPAIVs exhibited persistent and marked feather epitheliotropism in naturally infected commercial ducks. Infection of the feather epithelium resulted in epithelial necrosis and disruption, as well as the production and environmental shedding of infectious virions. Viral and feather antigens colocalized in dust samples obtained from poultry barns housing naturally infected birds. In summary, the feather epithelium contributes to viral replication, and it is a likely source of environmental infectious material. This underestimated excretion route could greatly impact the ecology of HPAIVs, facilitating airborne and preening-related infections within a flock, and promoting prolonged viral infectivity and long-distance viral transmission between poultry farms.

Autofluorescence microscopy as a non-invasive probe to characterize the complex mechanical properties of keratin-based integumentary organs: A feather paradigm

Integumentary organs exhibit diverse morphologies and functions. The complex mechanical property of the architecture is mainly contributed by the ingenious multiscale assembly of keratins. A cross-scale characterization on keratin integration in an integument system will help us understand the principles on how keratin-based bio-architecture are built and function in nature. In this study, we used feather as a model integument organ. We develop autofluorescence (AF) microscopy to study the characteristics of its keratin assemblies over a wide range of length scales. The AF intensity of each feather component, following the hierarchy from the rachis to barb to barbule, decreased with the physical dimension. By combining the analysis of AF signal and tensile testing, we can probe regional material density and the associated mechanical strength in a composite feather. We further demonstrated that the AF micro-images could resolve subtle variations in the defective keratin assembly in feathers from frizzled chicken variants with a mutation in α-keratin 75. The distinction between AF patterns and the morphological features of feather components across different length scales indicated a synergetic interplay between material integration and complex morphogenesis during feather development. The work shows AF microscopy can serve as an easy and non-invasive approach to study multiscale keratin organizations and the associated bio-mechanical properties in diverse integumentary organs. This approach will facilitate our learning of many bio-inspired designs in diverse animal integumentary organs/appendages.

Evo Devo of the Vertebrates Integument

All living jawed vertebrates possess teeth or did so ancestrally. Integumental surface also includes the cornea. Conversely, no other anatomical feature differentiates the clades so readily as skin appendages do, multicellular glands in amphibians, hair follicle/gland complexes in mammals, feathers in birds, and the different types of scales. Tooth-like scales are characteristic of chondrichthyans, while mineralized dermal scales are characteristic of bony fishes. Corneous epidermal scales might have appeared twice, in squamates, and on feet in avian lineages, but posteriorly to feathers. In contrast to the other skin appendages, the origin of multicellular glands of amphibians has never been addressed. In the seventies, pioneering dermal-epidermal recombination between chick, mouse and lizard embryos showed that: (1) the clade type of the appendage is determined by the epidermis; (2) their morphogenesis requires two groups of dermal messages, first for primordia formation, second for appendage final architecture; (3) the early messages were conserved during amniotes evolution. Molecular biology studies that have identified the involved pathways, extending those data to teeth and dermal scales, suggest that the different vertebrate skin appendages evolved in parallel from a shared placode/dermal cells unit, present in a common toothed ancestor, c.a. 420 mya.

Transglutaminase Activity Is Conserved in Stratified Epithelia and Skin Appendages of Mammals and Birds

The cross-linking of structural proteins is critical for establishing the mechanical stability of the epithelial compartments of the skin and skin appendages. The introduction of isopeptide bonds between glutamine and lysine residues depends on catalysis by transglutaminases and represents the main protein cross-linking mechanism besides the formation of disulfide bonds. Here, we used a fluorescent labeling protocol to localize the activity of transglutaminases on thin sections of the integument and its appendages in mammals and birds. In human tissues, transglutaminase activity was detected in the granular layer of the epidermis, suprabasal layers of the gingival epithelium, the duct of sweat glands, hair follicles and the nail matrix. In the skin appendages of chickens, transglutaminase activity was present in the claw matrix, the feather follicle sheath, the feather sheath and in differentiating keratinocytes of feather barb ridges. During chicken embryogenesis, active transglutaminase was found in the cornifying epidermis, the periderm and the subperiderm. Transglutaminase activity was also detected in the filiform papillae on the tongue of mice and in conical papillae on the tongue of chickens. In summary, our study reveals that transglutaminase activities are widely distributed in integumentary structures and suggests that transglutamination contributes to the cornification of hard skin appendages such as nails and feathers.

Optimization of feather degradation by a Bacillus thuringiensis isolate using response surface methodology and investigation of the feather protein hydrolysate structure

Valorization of chicken feather is a long-sought approach for its sustainable disposal. Being protein rich, hydrolyzed chicken feather has a wide range of applications, not limited to formulation of microbiological culture media, animal feed, and biofertilizers, but extends to synthesis of bioplastic films, cosmetics, and biomedicals. In this study, a potent keratinolytic isolate was recovered from soil and identified by 16S rRNA as Bacillus thuringiensis. Feather degradation by the isolate was optimized through response surface methodology. First, one-variable-at-a-time technique to assign the factors that affect feather degradation, then Box-Behnken central composite design model were employed. The model, involving three independent variables (initial pH, inoculum size, and concentration of supplementary glucose), was significant (R²  = 0.9716). According to the model, complete feather degradation is obtained at an inoculum size of B. thuringiensis B4 equal to 1 × 10¹⁰  CFU/ml, when feather meal broth is supplemented with 1.5% (w/v) glucose and pH adjusted to 8.5. Protein content of the lysate was 327.8 ± 25 μg/ml, and no carbohydrates were detected. SEM/EDX analysis has shown that the hydrolysate consisted mainly of O, P, S, and Se in addition to carbon, while FTIR images assured the presence of carboxyl and amino groups characteristic of peptides and amino acids.

Feather characteristics of loral zone in an insectivorous passerine: The Iberian gray shrike Lanius meridionalis, in southern France

In the French Mediterranean plain, the northern extreme of its native range, the Iberian gray shrike, Lanius meridionalis, predominantly feeds on arthropods. Its type of loral plumage plays a key role in protecting its eyes while transporting large prey. The aims are to understand the role played by feathers in protecting the animal from various types of defensive prey. I combine an inspection of large insect prey types found on larders with a review of bird specimens found in museum collections to examine the morphometric characteristics of rictal feathers and culmen. In addition, precision photographs are used to observe the posture of the plumage in natura. I could identify four categories of protective feathers: clustered bristles, semi-bristles, semi-plumes distributed in the loral area, and semi-plumes above the eyes. My results suggest that the Iberian gray shrike has a complex structure of loral feathers, specific to its foraging activity and prey types. The presence of these rictal bristles is probably a protection against the movements of larger prey items, which might damage loral zone of Lanius meridionalis.

Fluid drag reduction by penguin-mimetic laser-ablated riblets with yaw angles

The bodies of penguins, which swim underwater to forage, are densely covered with feathers, in which the barbs are oriented in the longitudinal direction. We hypothesize that these barbs act as riblets and reduce friction drag during swimming. Considering various real-world swim conditions, the drag reduction effect is expected to be robust against changes in the flow speed and yaw angle relative to the flow. To test this hypothesis, we created trapezoidal riblets based on the morphology of these barbs and measured the drag of flat plates with these fabricated riblets in a water tunnel. The spacing, width, and height of the barbs were found to be approximately 100, 60, and 30 μm, respectively. This spacing resulted in a nondimensional spacings⁺of 5.5 for a typical penguin swimming speed of 1.4 m s^-1. We fabricated four types of riblets on polyimide films by ultraviolet laser ablation. The first was a small-scale riblet for which the spacing was decreased to 41 μm to simulate the surface flow condition of the usual and slower swim behaviors in our water tunnel. The other three were manufactured to the actual scale of real barbs (spacing of 100 μm) with three different rib ridge widths: 10, 25, and 50 μm. Yaw angles of 0°, 15°, 30°, and 45° were also tested with the actual-scale riblets. The drag reduction rate of the small-scale riblet was maximized to 1.97% by the smallests⁺of 1.59. For all three actual-scale riblets, increasing the yaw angle from zero to 15° enhanced the drag reduction rate for the full range ofs⁺up to 13.5. The narrow-ridge riblet reduced drag at an even higher yaw angle of 45°, but the drag increased with zero yaw angle. Overall, the medium-ridge riblet, which was representative of the barbs, was well-balanced.

[Research advances in the impacts of oil pollutants on birds and the cleaning and repairing techniques]

Oil and its pollutants, which enter environment through natural oil seepage and many human activities, have considerable impacts on birds. We summarized the research advances in how oil pollutants influence birds and the cleaning technology of polluted birds and their habitats. The toxicity and destruction to feather structure are the major impacts of oil pollution on birds. Oil pollution can lead to birds' death, and also produce many chronic harms, including causing hemolytic anemia, reducing their immunity, disrupting thermal insulation and waterproo-fing performance of feather. It is an important way to reduce the impacts of oil pollution on birds by timely cleaning up the oil in bird habitats as well as carrying out the clean and repair work to the polluted birds. As a big oil-consuming country, China has been left behind by foreign countries in the studies of the effects of oil pollution on birds. More attention should be paid on the short-term and long-term impacts of oil pollution on birds and the cleaning and remediation technologies of the polluted birds and their habitats.

Biodegradable Nonwovens with Poultry Feather Addition as a Method for Recycling and Waste Management

Geotextiles are used for separation, drainage, filtration and anti-erosion protection sealing, as well as to improve plant vegetation conditions. The research objective of this study was to verify the influence of the addition of poultry feathers on accelerating the biodegradation of nonwovens in cultivated soil. The tests were carried out in laboratory conditions and were based on the assessment of weight loss. The experiments confirmed the positive effects of the presence of waste that was rich in keratin on the time required for the biodegradation of the tested materials (the period of biodegradation was 8–24 weeks). Additionally, the influence of the biodegradation of the tested materials on the ecotoxicity was investigated and showed no negative effects on the microbiological activity (10⁶ cfu). The research also included the determination of the carbon to nitrogen ratio of the test medium (blank, 12–14:1; with feather addition, 19–20:1). A statistical analysis revealed a correlation between the mechanical properties and the period of biological decomposition. This research was an important step for the management of poultry feather waste in agricultural applications. The tested materials could be seen an alternative that meets all ecological criteria, which seems to be a golden solution that not only allows the delivery of important nutrients to the soil, but also manages waste in an environmentally safe manner.

Primary Cell Lines From Feathers and Blood of Free-Living Tawny Owls (Strix aluco): A New In Vitro Tool for Non-Lethal Toxicological Studies

The validation of the use of primary cell lines from non-lethal matrixes of feathers and blood of nestlings of a wild bird species, the tawny owl (Strix aluco) is described. Tawny Owl Feather Fibroblast (TOFF) cells and peripheral blood mononuclear cells (PBMCs) were isolated and cultured from the pulp of the secondary wing feathers and whole blood respectively from free-living tawny owl nestlings. Cell growth was registered up until 48 h for both the PBMC cells and the TOFFs. The validation of these primary cell lines in free-living birds has the potential to advance the assessment of immunotoxicological effects in wildlife via non-lethal manner. They provide a key tool with which to study cell toxicity and responses to environmental stressors on a cellular level in wild bird species of interest.

Quantitative meta-analysis reveals no association between mercury contamination and body condition in birds

Mercury contamination is a major threat to the global environment, and is still increasing in some regions despite international regulations. The methylated form of mercury is hazardous to biota, yet its sublethal effects are difficult to detect in wildlife. Body condition can vary in response to stressors, but previous studies have shown mixed effects of mercury on body condition in wildlife. Using birds as study organisms, we provide the first quantitative synthesis of the effect of mercury on body condition in animals. In addition, we explored the influence of intrinsic, extrinsic and methodological factors potentially explaining cross-study heterogeneity in results. We considered experimental and correlative studies carried out in adult birds and chicks, and mercury exposure inferred from blood and feathers. Most experimental investigations (90%) showed a significant relationship between mercury concentrations and body condition. Experimental exposure to mercury disrupted nutrient (fat) metabolism, metabolic rates, and food intake, resulting in either positive or negative associations with body condition. Correlative studies also showed either positive or negative associations, of which only 14% were statistically significant. Therefore, the overall effect of mercury concentrations on body condition was null in both experimental (estimate ± SE = 0.262 ± 0.309, 20 effect sizes, five species) and correlative studies (-0.011 ± 0.020, 315 effect sizes, 145 species). The single and interactive effects of age class and tissue type were accounted for in meta-analytic models of the correlative data set, since chicks and adults, as well as blood and feathers, are known to behave differently in terms of mercury accumulation and health effects. Of the 15 moderators tested, only wintering status explained cross-study heterogeneity in the correlative data set: free-ranging wintering birds were more likely to show a negative association between mercury and body condition. However, wintering effect sizes were limited to passerines, further studies should thus confirm this trend in other taxa. Collectively, our results suggest that (i) effects of mercury on body condition are weak and mostly detectable under controlled conditions, and (ii) body condition indices are unreliable indicators of mercury sublethal effects in the wild. Food availability, feeding rates and other sources of variation that are challenging to quantify likely confound the association between mercury and body condition in natura. Future studies could explore the metabolic effects of mercury further using designs that allow for the estimation and/or manipulation of food intake in both wild and captive birds, especially in under-represented life-history stages such as migration and overwintering.

The Regulatory Microenvironment in Feathers of Chickens Infected with Very Virulent Marek's Disease Virus

Vaccines against Marek's disease can protect chickens against clinical disease; however, infected chickens continue to propagate the Marek's disease virus (MDV) in feather follicles and can shed the virus into the environment. Therefore, the present study investigated if MDV could induce an immunoregulatory microenvironment in feathers of chickens and whether vaccines can overcome the immune evasive mechanisms of MDV. The results showed an abundance of CD4+CD25+ and CD4+ transforming growth factor-beta (TGF-β)+ T regulatory cells in the feathers of MDV-infected chickens at 21 days post-infection. In contrast, vaccinated chickens had a lower number of regulatory T cells. Furthermore, the expression of TGF-β and programmed cell death receptor (PD)-1 increased considerably in the feathers of Marek's disease virus-infected chickens. The results of the present study raise the possibility of an immunoregulatory environment in the feather pulp of MDV-infected chickens, which may in turn favor replication of infectious MDV in this tissue. Exploring the evasive strategies employed by MDV will facilitate the development of control measures to prevent viral replication and transmission.

Systems for intricate patterning of the vertebrate anatomy

Periodic patterns form intricate arrays in the vertebrate anatomy, notably the hair and feather follicles of the skin, but also internally the villi of the gut and the many branches of the lung, kidney, mammary and salivary glands. These tissues are composite structures, being composed of adjoined epithelium and mesenchyme, and the patterns that arise within them require interaction between these two tissue layers. In embryonic development, cells change both their distribution and state in a periodic manner, defining the size and relative positions of these specialized structures. Their placement is determined by simple spacing mechanisms, with substantial evidence pointing to a variety of local enhancement/lateral inhibition systems underlying the breaking of symmetry. The nature of the cellular processes involved, however, has been less clear. While much attention has focused on intercellular soluble signals, such as protein growth factors, experimental evidence has grown for contributions of cell movement or mechanical forces to symmetry breaking. In the mesenchyme, unlike the epithelium, cells may move freely and can self-organize into aggregates by chemotaxis, or through generation and response to mechanical strain on their surrounding matrix. Different modes of self-organization may coexist, either coordinated into a single system or with hierarchical relationships. Consideration of a broad range of distinct biological processes is required to advance understanding of biological pattern formation. This article is part of the theme issue 'Recent progress and open frontiers in Turing's theory of morphogenesis'.

Evolution and development of parrot pseudoteeth

Parrot embryos carry peculiar appendages at their developing beak that have been described as pseudoteeth. To better characterize the pattern of development responsible for the emergence of these dental appendages, we examined parrot embryos combining conventional histology and microtomography approaches. Using immunohistochemistry, we observed the epithelial and mesenchymal expression of several proteins involved in tooth development in mammals. Parrot pseudoteeth arose by epithelial and mesenchymal evagination, and their early development was similar to the ontogeny of scales and feathers. There was no enamel tissue, and the evaginations were surrounded by the rhamphotheca. In adults, the rhamphotheca covers entirely the appendages, now represented by bone evaginations, which were more numerous in the lower than in the upper beak, being similar to the osseous teeth of the fossil Pelagornithidae. These embryonic pseudoteeth resembled reptile's first-generation teeth and dental appendages of chicken talpid² mutants. Proteins involved in mammalian odontogenesis, such as SHH, BMP4, PITX2, and PAX9, were found to be generally expressed in beak epithelium and mesenchyme during parrot pseudoteeth development, with clusters of high-level expression in the pseudoteeth rudiments. This suggests that a similar, highly conserved gene expression program gives rise to the appearance of odontode derivatives in numerous species, despite their divergent developmental paths. These results provide new insights into the development and evolution of odontode-derived structures in vertebrates.

Nutrient sources for offspring formation: diet-mother and mother-offspring isotope discrimination in domesticated gallinaceous birds

Stable isotope techniques can be used to assess nutrient acquisition and allocation strategies used to produce offspring. Before stable isotope techniques can be employed, researchers need reliable isotope discrimination values. In this context, isotope discrimination compares the difference in the isotope ratio between the maternal-offspring tissue that occurs during nutrient transfer prior to egg laying. Currently, isotope discrimination values are unknown between the maternal blood constituents - that reflect different temporal scales of integration - and downy feathers of their offspring. In this study, we experimentally derive isotope discrimination relationships between maternal diet-blood constituents for egg laying, and between maternal blood constituents-down feathers of offspring in an experiment with 3 types of domesticated gallinaceous birds raised on known diets. Our experiment is the first to report isotope discrimination values for maternal blood constituents-down of offspring in avian taxa and provides a new sampling technique that is less invasive than previously available as collecting down does not require sampling viable eggs or individuals. Future researchers can use these results to assist in identifying nutrient sources used by adult birds to produce young.

An Early Cretaceous enantiornithine bird with a pintail

Enantiornithes are the most successful group of Mesozoic birds, arguably representing the first global avian radiation,^1-4 and commonly resolved as the sister to the Ornithuromorpha, the clade within which all living birds are nested.^1,3 The wealth of fossils makes it feasible to comparatively test evolutionary hypotheses about the pattern and mode of eco-morphological diversity of these sister clades that co-existed for approximately 65 Ma. Here, we report a new Early Cretaceous enantiornithine, Yuanchuavis kompsosoura gen. et. sp. nov., with a rectricial fan combined with an elongate central pair of fully pennaceous rachis-dominated plumes, constituting a new tail plumage previously unknown among nonavialan dinosaurs and Mesozoic birds but which strongly resembles the pintail in many neornithines. The extravagant but aerodynamically costly long central plumes, as an honest signal of quality, likely evolved in enantiornithines through the handicap process of sexual selection. The contrasting tail morphotypes observed between enantiornithines and early ornithuromorphs reflect the complex interplay between sexual and natural selections and indicate that each lineage experienced unique pressures reflecting ecological differences. As in neornithines, early avialans repeatedly evolved extravagant structures highlighting the importance of sexual selection in shaping the plumage of feathered dinosaurs, even early in their evolutionary history.

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs

Carotenoids are pigments responsible for most bright yellow, red, and orange hues in birds. Their distribution has been investigated in avian plumage, but the evolution of their expression in skin and other integumentary structures has not been approached in detail. Here, we investigate the expression of carotenoid-consistent coloration across tissue types in all extant, nonpasserine species (n = 4022) and archelosaur outgroups in a phylogenetic framework. We collect dietary data for a subset of birds and investigate how dietary carotenoid intake may relate to carotenoid expression in various tissues. We find that carotenoid-consistent expression in skin or nonplumage keratin has a 50% probability of being present in the most recent common ancestor of Archosauria. Skin expression has a similar probability at the base of the avian crown clade, but plumage expression is unambiguously absent in that ancestor and shows hundreds of independent gains within nonpasserine neognaths, consistent with previous studies. Although our data do not support a strict sequence of tissue expression in nonpasserine birds, we find support that expression of carotenoid-consistent color in nonplumage integument structures might evolve in a correlated manner and feathers are rarely the only region of expression. Taxa with diets high in carotenoid content also show expression in more body regions and tissue types. Our results may inform targeted assays for carotenoids in tissues other than feathers, and expectations of these pigments in nonavian dinosaurs. In extinct groups, bare-skin regions and the rhamphotheca, especially in species with diets rich in plants, may express these pigments, which are not expected in feathers or feather homologues.

Research Note: It's not just stress-fecal contamination of plumage may affect feather corticosterone concentration

The feather corticosterone concentration (fCORT) is increasingly used to assess long-term stress in birds as this indicator provides the potential to retrospectively evaluate the adrenocortical activity of a bird during the growth period of a feather over several weeks in one sample. However, there is still a lack of knowledge concerning external factors which can potentially influence fCORT in birds. The aim of the present study was to determine whether fCORT in laying hens is affected by previous fecal contamination of the plumage. Fully grown primaries 5 (P5s) of laying hens (n = 40) were used for the study. To test the effects of fecal contamination on fCORT, freshly defecated droppings from laying hens were collected and mixed manually. In order to simulate practical and at the same time standardized contamination, the upper surface of the previously determined middle third of the right P5 of each hen then was evenly coated with the paste prepared from fresh feces. The treated feathers were stored for 24 h protected from light at room temperature under a film cover to prevent evaporation. Thereafter, the applied layer of excreta was removed manually. Contralateral P5s of the same individuals were stored under identical conditions and served as controls. Both treatment and control feathers were washed in an aqueous soap solution, rinsed several times in pure water and air-dried subsequently. After pulverization and methanolic extraction, fCORT was analyzed by ELISA. The mean fCORT of treatment P5s (reference ‘feather length’: 12.88 ± 3.16 pg/mm; reference ‘feather weight’: 7.81 pg/mg ± 1.86 pg/mg) were significantly higher (P < 0.001) than those of control P5s (reference ‘feather length’: 9.76 ± 2.42 pg/mm; reference ‘feather weight’: 5.93 ± 1.44 pg/mg). Our results show that previous contamination with excreta can increase fCORT, which was detectable even after a washing procedure prior to analysis. In conclusion, fecal contamination of feathers is a significant influencing factor that has to be considered when applying fCORT measurements.

Regional Specific Differentiation of Integumentary Organs: Regulation of Gene Clusters within the Avian Epidermal Differentiation Complex and Impacts of SATB2 Overexpression

The epidermal differentiation complex (EDC) encodes a group of unique proteins expressed in late epidermal differentiation. The EDC gave integuments new physicochemical properties and is critical in evolution. Recently, we showed β-keratins, members of the EDC, undergo gene cluster switching with overexpression of SATB2 (Special AT-rich binding protein-2), considered a chromatin regulator. We wondered whether this unique regulatory mechanism is specific to β-keratins or may be derived from and common to EDC members. Here we explore (1) the systematic expression patterns of non-β-keratin EDC genes and their preferential expression in different skin appendages during development, (2) whether the expression of non-β-keratin EDC sub-clusters are also regulated in clusters by SATB2. We analyzed bulk RNA-seq and ChIP-seq data and also evaluated the disrupted expression patterns caused by overexpressing SATB2. The results show that the expression of whole EDDA and EDQM sub-clusters are possibly mediated by enhancers in E14-feathers. Overexpressing SATB2 down-regulates the enriched EDCRP sub-cluster in feathers and the EDCH sub-cluster in beaks. These results reveal the potential of complex epigenetic regulation activities within the avian EDC, implying transcriptional regulation of EDC members acting at the gene and/or gene cluster level in a temporal and skin regional-specific fashion, which may contribute to the evolution of diverse avian integuments.

Comparison of Feather Damage Associated With the Application of Pressure-sensitive Adhesive Tapes

Pressure-sensitive adhesive tapes are commonly used for the positioning of birds for radiography and securing bandages. The effect of 5 common tapes on feather structure was investigated with before-and-after comparisons. Each tape demonstrated a characteristic pattern of damage to the feather vane that involved separation of barbules and/or tearing of barbs. Tapes with rigid backing materials and strong adhesives were more likely to cause tearing and barbule separation, respectively, whereas flexible tapes with limited adhesion to feathers were more successful in securing feathers without causing irreparable damage. Consideration should be given to the appropriate selection of tape applied to the feathers of birds to prevent iatrogenic damage to their plumage.

Keratinases Produced by Aspergillus stelliformis, Aspergillus sydowii, and Fusarium brachygibbosum Isolated from Human Hair: Yield and Activity

Twenty fungal strains belonging to 17 species and isolated from male scalp hair were tested for their capacity to hydrolyze keratinous material from chicken feather. The identification of the three most efficient species was confirmed by sequencing of the internal transcribed spacer (ITS) region of rDNA. Activities of fungal keratinases produced by Aspergillus stelliformis (strain AUMC 10920), A. sydowii (AUMC 10935), and Fusarium brachygibbosum (AUMC 10937) were 113, 120, and 130 IU mg⁻¹ enzymes, respectively. The most favorable conditions were at pH 8.0 and 50 °C. Keratinase activity was markedly inhibited by EDTA and metal ions Ca⁺², Co⁺², Ni⁺², Cu⁺², Fe⁺², Mg⁺², and Zn⁺², with differences between the fungal species. To the best of our knowledge, this is the first study on the activity of keratinase produced by A. stelliformis, A. sydowii, and F. brachygibbosum. F. brachygibbosum keratinase was the most active, but the species is not recommended because of its known phytopathogenicty. Aspergillus sydowii has many known biotechnological solutions and here we add another application of the species, as producer of keratinases. We introduce A. stelliformis as new producer of active fungal keratinases for biotechnological solutions, such as in the management of keratinous waste in poultry industry.

Web databases of feather photographs are useful tools for avian morphometry studies

Wing area, wing loading, and aspect ratio are key variables for studies of avian comparative ecology, despite the complexity of measuring wing characteristics in living and museum specimens. The systematic databases of feather photographs available on the Internet may offer an alternative way of obtaining such morphometric data. Here, we evaluate whether measurements of scanned feathers from web photograph databases may offer reliable estimates of avian morphometry.Published data on wing area were obtained for 317 bird species and feather measurements from web photograph databases for 225 of them. A variable termed "lift generation area," a proxy for wing area, was calculated for each species on the basis of the mean length of the five distal secondary feathers and wingspan data from literature. The fit between this proposed variable and data extracted from the literature was examined by correlation, employing linear regression to explore the lack of fit among species."Lift generation area" proved to be highly informative as a proxy for wing area for the study species as a whole (R 2 > .98). Discrepancies observed between species were strongly negatively associated with the size of the original sample used to calculate wing area (p = .001) and, to a lesser extent, with bird size (p = .023), but not with aspect ratio. It was also found that the mean value of the mismatch between "lift generation area" and wing area (13.1%) among the study species as a whole was of similar magnitude to that found between sources of bibliographic wing area data for the 64 species for which two published estimates of this variable were available (15.3%).We conclude that measurements made from feather photograph databases are reliable for use in studies of avian comparative ecology, enabling the inclusion of biomechanical parameters of many more species than featured at present.

Flexible Flaps Inspired by Avian Feathers Can Enhance Aerodynamic Robustness in low Reynolds Number Airfoils

Unlike rigid rotors of drones, bird wings are composed of flexible feathers that can passively deform while achieving remarkable aerodynamic robustness in response to wind gusts. In this study, we conduct an experimental study on the effects of the flexible flaps inspired by the covert of bird wings on aerodynamic characteristics of fixed-wings in disturbances. Through force measurements and flow visualization in a low-speed wind tunnel, it is found that the flexible flaps can suppress the large-scale vortex shedding and hence reduce the fluctuations of aerodynamic forces in a disturbed flow behind an oscillating plate. Our results demonstrate that the stiffness of the flaps strongly affects the aerodynamic performance, and the force fluctuations are observed to be reduced when the deformation synchronizes with the strong vortex generation. The results point out that the simple attachment of the flexible flaps on the upper surface of the wing is an effective method, providing a novel biomimetic design to improve the aerodynamic robustness of small-scale drones with fixed-wings operating in unpredictable aerial environments.

Acute exacerbation in chronic bird fancier's lung with pleuroparenchymal fibroelastosis

A 71-year-old non-smoker woman was admitted to our hospital complaining of a six-month history of dry cough. She had kept java sparrow for nine years and has been raising budgerigars for the previous eight months. High-resolution computed tomography (HRCT) images of the chest revealed reticulonodular lesions predominantly in the bilateral upper lobes. Surgical lung biopsy specimens showed non-caseous epithelioid cell granulomas in the alveolar spaces, including irregular and centrilobular fibrosis with pleuroparenchymal fibroelastosis. When she started using a duck feather duvet at home, she developed dyspnoea and chest HRCT abnormalities progressively deteriorated. The results of precipitation of antibodies against duck feather, java sparrow, and budgerigars dropping extracts were positive in sera. Consequently, the patient was diagnosed as having chronic bird fancier's lung with acute exacerbation caused by the use of a feather duvet. After combination treatments with corticosteroid and cyclosporine, her respiratory symptoms and reticulonodular shadow immediately improved.

Folding Keratin Gene Clusters during Skin Regional Specification

Regional specification is critical for skin development, regeneration, and evolution. The contribution of epigenetics in this process remains unknown. Here, using avian epidermis, we find two major strategies regulate β-keratin gene clusters. (1) Over the body, macro-regional specificities (scales, feathers, claws, etc.) established by typical enhancers control five subclusters located within the epidermal differentiation complex on chromosome 25; (2) within a feather, micro-regional specificities are orchestrated by temporospatial chromatin looping of the feather β-keratin gene cluster on chromosome 27. Analyses suggest a three-factor model for regional specification: competence factors (e.g., AP1) make chromatin accessible, regional specifiers (e.g., Zic1) target specific genome regions, and chromatin regulators (e.g., CTCF and SATBs) establish looping configurations. Gene perturbations disrupt morphogenesis and histo-differentiation. This chicken skin paradigm advances our understanding of how regulation of big gene clusters can set up a two-dimensional body surface map.

The effect of dietary energy and protein level on feather, skin and nodule growth of the ostrich (Struthio camelus)

Accurate diet formulations are required to fulfil the nutrient requirements of birds in order to achieve optimal production. Knowing how the skin, nodule and feather production characteristics vary with diets of different nutrient densities will help in least-cost modelling. Feather growth and nodule development are factors that were previously neglected in ostrich diet formulation, both of which are essential for the development of a predictive production model. In this trial, 120 birds were placed in 15 pens. Varying energy regimes (high, medium and low) and accompanying protein and amino acid profile levels (level 1–5) were assigned ad libitum to each pen. A randomly selected bird from each pen was slaughtered at 1, 35, 63, 103, 159, 168 and 244 days of age. During the slaughter, each bird was weighed, stunned, exsanguinated, defeathered and eviscerated. Feathers from four regions of the skin were plucked and weighed. The shaft diameter of the wing feathers was measured. The nodule size of the tanned skin was measured for each slaughter age. The data were transformed to natural logarithms and regressed against the total feather weight and the total featherless empty body protein weight to set up allometric growth equations. A prediction equation to determine nodule size of the live bird was proposed. Feed cost optimisation is paramount, and results from this study will aid in setting up least-cost optimisation (simulation) formulation models.

Monitoring Phytate Hydrolysis Using Serial Blood Sampling and Feather Myo-Inositol Levels in Broilers

Phytate forms insoluble precipitates with various cations that are recalcitrant to digestion in poultry. Dietary supplementation with exogenous phytase has been shown to improve phytate solubility and digestibility and, in turn, improve animal growth performance. Although the kinetics of phytate hydrolysis by exogenous phytase are well described in vitro, the progression of the reaction in vivo is still not well defined. The aim of the present study was, therefore, to monitor the kinetic variation of myo-inositol (myo-Ins) levels in both circulation and feather following exogenous phytase supplementation. In experiment 1, 4 week-old male broilers were individually housed with ad libitum access to water and a standard commercial diet. Birds were maintained under environmental temperature of 24°C and 30% RH. Birds were cannulated in the cutaneous ulnar vein on the right wing and remained untouched for 3 days. On the day of the experiment, birds were randomly divided into three body weight-matched groups and fed either the control diet, the control diet-supplemented with myo-Ins or Ronozyme HiPhos (0.06%, DSM Nutritional Products, Switzerland) for 10 h. In the experiment 2, birds were fed only HiPhos for 30 h. Growing feathers and blood were collected at baseline and then every 2 h for 10 h (experiment 1) and 30 h (experiment 2) post-prandially. Plasma and feather myo-Ins levels were determined by UHPLC-MS/MS. The relative expression of inositol polyphosphate-1-phosphatase (INPP1), inositol hexakisphosphate kinase 1-3 (IP6K1-3), inositol-3-phosphate synthase (ISYNA), and multiple inositol-polyphosphate phosphatase 1 (MNPP1) genes in blood and feathers was determined by real-time qPCR using 2^–ΔΔCt method. Plasma and feather myo-Ins levels were significantly increased by HiPhos at 6 h to 8 h post-prandial. The mRNA abundances of INPP1, IP6K1, and ISYNA in the circulation were significantly down regulated at all periods compared to the baseline levels. IP6K2, IP6K3, and MINPP1 gene expression, however, was up regulated at 8 h post-prandial and then returned to the baseline levels. In feathers, the expression of INPP1 was induced at 8 h post-prandial and remained higher compared to the baseline. The expression of IP6K2, IP6K3, and MINPP1 was down regulated during the first 10 h and then returned to baseline levels for the rest of the post-prandial period. Taken together, our data show that phytase modulates the expression of genes associated with myo-Ins metabolism and generates release of myo-Ins in both circulation and feather at 6–10 h post-feeding. Feather myo-Ins concentration could be used as a non-invasive method to monitor phytate hydrolysis in practice.

Methionine improves feather follicle development in chick embryos by activating Wnt/β-catenin signaling

This study was conducted to explore the regulatory role of methionine (Met) in feather follicle and feather development during the embryonic period of chicks. A total of 280 fertile eggs (40 eggs/group) were injected with 0, 5, 10, 20 mg of L-Met or DL-Met/per egg on embryonic day 9 (E9), and whole-body feather and skin tissues were collected on E15 and the day of hatching (DOH). The whole-body feather weight was determined to describe the feather growth, and the skin samples were subjected to hematoxylin and eosin staining and Western blotting for the evaluation of feather follicle development and the expressions of Wingless/Int (Wnt)/β-catenin signaling pathway proteins, respectively. The results showed that L- or DL-Met did not affect the embryo weight (P > 0.05), but increased the absolute and relative whole-body feather weights. Specifically, 5 and 10 mg of L-Met and 5, 10, and 20 mg of DL-Met significantly increased the absolute feather weight at E15 (P < 0.05), and 10 mg of L-Met and 5 and 10 mg of DL-Met significantly increased the absolute and relative feather weight on the DOH (P < 0.05). Moreover, a main effect analysis suggested that changes in the embryo and feather weights were related to the Met levels (P < 0.05) but not the Met source (P > 0.05). The levels of L- and DL-Met were quadratically correlated with the absolute and relative feather weights of chicks on the DOH (P < 0.05). Correspondingly, all doses of L- and DL-Met significantly increased the diameter and density of feather follicles on the DOH (P < 0.05), as well as the activity of Wnt/β-catenin on E15 and the DOH (P < 0.05). In conclusion, injection of either L- or DL-Met can improve feather follicle development by activating Wnt/β-catenin signaling, and thereby promoting feather growth; furthermore, no difference in feather growth was found between L- and DL-Met treatments. Our findings might provide a nutritional intervention for regulating feather growth in poultry production.

The vertical transmission of antibiotic residues from parent hens to broilers

Imprudent and superfluous use of antibiotics contributes to the selection of resistant bacteria, which is a large threat to human health. Therefore analytical procedures have been implemented in the poultry production sector to check if antibiotic treatments are registered, aiming to achieve more prudent use of antibiotics. These methods rely on the analysis of feathers, a matrix in which antibiotic residues persist. However, other routes besides direct administration, through which poultry feathers could contain antibiotic residues, should also be taken into account. In this research the vertical transmission from parent hen to broiler was investigated through a controlled animal study for the antibiotics enrofloxacin, doxycycline and sulfachlorpyridazine. Vertical transmission was observed for all antibiotics to both egg and egg shell. Also it is demonstrated that the transferred antibiotics from parent hen to chick are subsequently excreted via the chick's droppings. Through this route, the broilers' environment is contaminated. If eggs are hatched that were taken during treatment of the parent hen, this indirect route and/or the direct vertical transmission can eventually result in the detection of low concentrations of antibiotic residues in the broilers' feathers at greater age: <50 µg kg^-1 for freely extractable residues and <10 µg kg^-1 for non-freely extractable residues. No antibiotics were detected in the broilers' muscle or kidney from 4 weeks of age. This research provides relevant information regarding the possible amount of residues originating from vertical transmission when monitoring matrices such as feathers and broiler droppings in order to stimulate correct use and registration of antibiotics in the poultry sector.

Molecular Signaling and Nutritional Regulation in the Context of Poultry Feather Growth and Regeneration

The normal growth and regeneration of feathers is important for improving the welfare and economic value of poultry. Feather follicle stem cells are the basis for driving feather development and are regulated by various molecular signaling pathways in the feather follicle microenvironment. To date, the roles of the Wnt, Bone Morphogenetic Protein (BMP), Notch, and Sonic Hedgehog (SHH) signaling pathways in the regulation of feather growth and regeneration are among the best understood. While these pathways regulate feather morphogenesis in different stages, their dysregulation results in a low feather growth rate, poor quality of plumage, and depilation. Additionally, exogenous nutrient intervention can affect the feather follicle cycle, promote the formation of the feather shaft and feather branches, preventing plumage abnormalities. This review focuses on our understanding of the signaling pathways involved in the transcriptional control of feather morphogenesis and explores the impact of nutritional factors on feather growth and regeneration in poultry. This work may help to develop novel mechanisms by which follicle stem cells can be manipulated to produce superior plumage that enhances poultry carcass quality.

Rectricectomy With Pygostylectomy for Resolution of Feather Trauma in an Umbrella Cockatoo (Cacatua alba)

Feather trauma is a common problem among pet birds, especially those with trimmed wing feathers, and often affects remiges and rectrices. Damage can become chronic if new feathers remain unprotected by fully formed adjacent feathers. The follicles can become damaged and poorly functional over time. A 6-month-old male umbrella cockatoo (Cacatua alba) was presented for examination because of feather damage that occurred shortly after receiving a wing trim by the owner. Over the next 18 months, various medical, behavioral, and husbandry methods failed to allow normal regrowth of the tail feathers. The bird presented 25 times over the 18-month period for problems associated with broken blood feathers in the tail. Feather imping was ruled out because of the lack of hollow adult shafts to serve as a base. Diagnostic tests included hematologic testing and biochemical analysis, circovirus testing, feather biopsy, and radiographs, results of which were unremarkable. Because of the chronic pain associated with the frequent rectrix damage, a complete rectricectomy was performed. All of the rectrical follicles as well as the pygostyle were surgically removed. Healing was uneventful and the bird has been clinically normal with no further blood feather injury for 24 months after surgery.

Feather HSP70: a novel non-invasive molecular marker for monitoring stress induced by heat exposure in broilers

Poultry well-being and economic burden due to heat stress (HS) are of great importance to the poultry industry. Efficient design and effective evaluation of any strategies to alleviate the adverse effects of HS on poultry production require an accurate measurement of stress. However, current methods for monitoring stress in poultry are less than ideal, as they are invasive or subjective, and therefore variable. Here, we demonstrated that HSP70, the well-established intracellular stress chaperone, is expressed in chicken feather and is responsive to HS, and could therefore be used as a stress marker. Growing feathers were collected from the same bird (Cobb500, n = 9) in the morning (barn temperature 24°C) and afternoon (barn temperature 29.5°C) in the summer (2016 June 21) in Arkansas, USA. In the afternoon, the birds were panting and their core body temperatures were significantly higher compared to the morning time, as illustrated by iButton data thermo-loggers. Concomitantly, blood HSP70 mRNA and feather HSP70 expression (mRNA and protein) were significantly increased in the afternoon compared to the morning time. Similarly, HSP70 protein expression in the duodenum was also significantly higher in the afternoon compared to the morning period. Together, these finding identify feather HSP70 as a novel non-invasive molecular signature that mirrors the intracellular and systemic stress, which can be useful to monitor well-being of chickens and other avian species under different challenges.

Of 11 candidate steroids, corticosterone concentration standardized for mass is the most reliable steroid biomarker of nutritional stress across different feather types

Measuring corticosterone in feathers has become an informative tool in avian ecology, enabling researchers to investigate carry-over effects and responses to environmental variability. Few studies have, however, explored whether corticosterone is the only hormone expressed in feathers and is the most indicative of environmental stress. Essential questions remain as to how to compare hormone concentrations across different types of feathers and whether preening adds steroids, applied after feather growth.We used liquid chromatography coupled to tandem mass spectrometry to quantify a suite of 11 steroid hormones in back, breast, tail, and primary feathers naturally grown at overlapping time intervals by rhinoceros auklet Cerorhinca monocerata captive-reared fledglings and wild-caught juveniles. The captive-reared birds were raised on either a restricted or control diet. Measured steroids included intermediates in the adrenal steroidogenesis pathway to glucocorticoids and the sex steroids pathway to androgens and estrogens.Corticosterone was detected in the majority of feathers of each type. We also detected cortisone in back feathers, androstenedione in breast feathers, and testosterone in primary feathers. Captive fledglings raised on a restricted diet had higher concentrations of corticosterone in all four feather types than captive fledglings raised on a control diet. Corticosterone concentrations were reliably repeatable across feather types when standardized for feather mass, but not for feather length. Of the seven hormones looked for in uropygial gland secretions, only corticosterone was detected in one out of 23 samples.We conclude that corticosterone is the best feather-steroid biomarker for detection of developmental nutritional stress, as it was the only hormone to manifest a signal of nutritional stress, and that exposure to stress can be compared among different feather types when corticosterone concentrations are standardized by feather mass.

The Early Origin of Feathers

Feathers have long been regarded as the innovation that drove the success of birds. However, feathers have been reported from close dinosaurian relatives of birds, and now from ornithischian dinosaurs and pterosaurs, the cousins of dinosaurs. Incomplete preservation makes these reports controversial. If true, these findings shift the origin of feathers back 80 million years before the origin of birds. Gene regulatory networks show the deep homology of scales, feathers, and hairs. Hair and feathers likely evolved in the Early Triassic ancestors of mammals and birds, at a time when synapsids and archosaurs show independent evidence of higher metabolic rates (erect gait and endothermy), as part of a major resetting of terrestrial ecosystems following the devastating end-Permian mass extinction.

Self-assembly of biological networks via adaptive patterning revealed by avian intradermal muscle network formation

Networked structures integrate numerous elements into one functional unit, while providing a balance between efficiency, robustness, and flexibility. Understanding how biological networks self-assemble will provide insights into how these features arise. Here, we demonstrate how nature forms exquisite muscle networks that can repair, regenerate, and adapt to external perturbations using the feather muscle network in chicken embryos as a paradigm. The self-assembled muscle networks arise through the implementation of a few simple rules. Muscle fibers extend outward from feather buds in every direction, but only those muscle fibers able to connect to neighboring buds are eventually stabilized. After forming such a nearest-neighbor configuration, the network can be reconfigured, adapting to perturbed bud arrangement or mechanical cues. Our computational model provides a bioinspired algorithm for network self-assembly, with intrinsic or extrinsic cues necessary and sufficient to guide the formation of these regenerative networks. These robust principles may serve as a useful guide for assembling adaptive networks in other contexts.

How chemotherapy and radiotherapy damage the tissue: Comparative biology lessons from feather and hair models

Chemotherapy and radiotherapy are common modalities for cancer treatment. While targeting rapidly growing cancer cells, they also damage normal tissues and cause adverse effects. From the initial insult such as DNA double-strand break, production of reactive oxygen species (ROS) and a general stress response, there are complex regulatory mechanisms that control the actual tissue damage process. Besides apoptosis, a range of outcomes for the damaged cells are possible including cell cycle arrest, senescence, mitotic catastrophe, and inflammatory responses and fibrosis at the tissue level. Feather and hair are among the most actively proliferating (mini-)organs and are highly susceptible to both chemotherapy and radiotherapy damage, thus provide excellent, experimentally tractable model systems for dissecting how normal tissues respond to such injuries. Taking a comparative biology approach to investigate this has turned out to be particularly productive. Started in chicken feather and then extended to murine hair follicles, it was revealed that in addition to p53-mediated apoptosis, several other previously overlooked mechanisms are involved. Specifically, Shh, Wnt, mTOR, cytokine signalling and ROS-mediated degradation of adherens junctions have been implicated in the damage and/or reparative regeneration process. Moreover, we show here that inflammatory responses, which can be prominent upon histological examination of chemo- or radiotherapy-damaged hair follicle, may not be essential for the hair loss phenotype. These studies point to fundamental, evolutionarily conserved mechanisms in controlling tissue responses in vivo, and suggest novel strategies for the prevention and management of adverse effects that arise from chemo- or radiotherapy.

Integrated tool for microsatellite isolation and validation from the reference genome and their application in the study of breeding turnover in an endangered avian population

Accurate individual identification is required to estimate survival rates in avian populations. For endangered species, non-invasive methods of obtaining individual identification, such as using molted feathers as a source of DNA for microsatellite markers, are preferred because of less disturbance, easy sample preparation and high efficiency. With the availability of many avian genomes, a few pipelines isolating genome-wide microsatellites have been published, but it is still a challenge to isolate microsatellites from the reference genome efficiently. Here, we have developed an integrated tool comprising a bioinformatic pipeline and experimental procedures for microsatellite isolation and validation based on the reference genome. We have identified over 95 000 microsatellite loci and established a system comprising 10 highly polymorphic markers (PIC value: 0.49-0.93, mean: 0.79) for an endangered species, saker falcon (Falco cherrug). These markers (except 1) were successfully amplified in 126 molted feathers, exhibiting high amplification success rates (83.9-99.7%), high quality index (0.90-0.97) and low allelic dropout rates (1-9.5%). To further assess the efficiency of this marker system in a population study, we identified individual sakers using these molted feathers (adult) and 146 plucked feathers (offspring). The use of parent and offspring samples enabled us to infer the genotype of missing samples (N = 28), and all adult genotypes were used to ascertain that breeding turnover is a useful proxy for survival estimation in sakers. Our study presents a cost-effective tool for microsatellite isolation based on publicly available reference genomes and demonstrates the power of this tool in estimating key parameters of avian population dynamics.

Ultraviolet Reflectance Structures of Peacock Feathers

Male peacock (Pavo cristatus) tail feathers have an eyespot pattern with an inconspicuous black or dark blue center surrounded by brilliant, structural colors, such as blue, light brown, and yellow-green. Under ultraviolet A (UVA), the central part of the eyespot reflects UVA better than the surrounding parts. Herein, I examined various areas of eyespots on paraffin sections of feathers using an optical microscope, and characterized positional relationships between barbs and barbules. These analyses confirmed that barbules in the central part of the eyespot are in a horizontal position with respect to the barb, and that light transmission from the central part is less than that from the other parts. In addition, I compared microstructures of barbules in the central part of eyespot with those in surrounding areas using transmission electron microscope analysis. The melanin rods in the barbules reflecting yellow-green color comprise several ordered lattice structures. In contrast, melanin rods in the central part of the eyespot were only distributed in 1-3 layers on a part of the front side of the barbules. I also demonstrated that keratin structures of barbules are homogeneous in the central part of the eyespot, but have fibrous structures with many voids in the yellow-green parts. Collectively, the present observations suggest that feathers in the central part of the eyespot reflect UVA depending on the direction of irradiation, and these properties are governed by configurations of barbules relative to barbs, melanin rod distributions, and the presence of keratin structures with gaps.

Repairable cascaded slide-lock system endows bird feathers with tear-resistance and superdurability

Bird feathers have aroused tremendous attention for their superdurability against tears during long flights through wind and even bushes. Although feathers may inevitably be unzipped, the separated feather vanes can be repaired easily by bill stroking. However, the mechanism underlying bird feathers' superdurability against tears remains unclear. Here, we reveal that the superdurability of bird feathers arises from their repairable cascaded slide-lock system, which is composed of hooklets, a slide rail, and spines at the end of the slide rail as terminating structures. Microscopy with a micronano manipulating system and 3D X-ray microscopy provided high-level visibility into the 3D fine structures and the entire unzipping process of feathers. The hooklets can slide along the slide rail reversibly when suffering external forces, and the sliding hooklet can be locked by the spine at the ends of barbules when larger pulling forces are applied and even slide farther away due to the unzipping of the interlocking structure with large deformation of the barbules. The elongation before separation of adjacent barbs can reach up to 270%, and the separation force can be maintained above 80% of the initial value even after 1,000 cycles of separating and repairing. These results prove that the cascaded slide-lock system ensures the superdurability of bird feathers against tears.

Biological responses to environmental contamination. How can metal pollution impact signal honesty in avian species?

Environmental pollution, for example with metals, can significantly affect the ecosystem balance leading to severe changes. Biologically active pigments are relevant for the appearance and condition of birds. Melanin and carotenoid particles are the most frequently deposited pigments in avian integument. They are responsible for the majority of colors of bird plumage. The phenotypic expression can be affected by metal contamination. It can be manifested as color bleaching or differences in the size of plumage badges. In this study, we performed a comprehensive review of related studies in order to estimate the underlying population effect of this potential dependency. The study is based on the review of the literature regarding several avian species. It was designed to identify an area where the effect of the exposure is still poorly known. The analysis was specifically conducted to investigate the correlation between trace element concentration and eumelanin deposition. Moreover, we searched for factors that could affect spectral properties of feathers with carotenoid-based pigmentation. As a result, we found carotenoid-based pigmentation to be of a good use in terms of visual condition assessment. Changes in melanin-based pattern should be analyzed separately for eu- and pheomelanin as well as for a range of essential and toxic elements. Comprehensive studies on the subject are still scarce. Therefore, the issue requires further investigation.

A Potential Role for MMPs during the Formation of Non-Neurogenic Placodes

The formation of non-neurogenic placodes is critical prior to the development of several epithelial derivatives (e.g., feathers, teeth, etc.) and their development frequently involves morphogenetic proteins (or morphogens). Matrix metalloproteinases (MMPs) are important enzymes involved in extracellular matrix remodeling, and recent research has shown that the extracellular matrix (ECM) can modulate morphogen diffusion and cell behaviors. This review summarizes the known roles of MMPs during the development of non-neurogenic structures that involve a placodal stage. Specifically, we discuss feather, hair, tooth, mammary gland and lens development. This review highlights the potential critical role MMPs may play during placode formation in these systems.

MC1R polymorphism associated with plumage color variations in Coturnix chinensis

The melanocortin 1 receptor (MC1R) gene was investigated as a candidate for plumage variations in Chinese painted quail, Coturnix chinensis. Four silent and two missense nucleotide polymorphisms were identified. The correspondent amino acid changes, p.Glu92Lys and p.Pro292Leu, were found in Blue Face and Red Breasted animals respectively. Blue Face is a melanic phenotype similar to the co-dominant Extended Brown of Japanese quail, and both share the p.Glu92Lys mutation. The association of p.Pro292Leu with the recessive Red Breasted was confirmed in 23 animals from an experimental F2 cross.

DETERMINING RAPTOR SPECIES AND TISSUE SENSITIVITY FOR IMPROVED WEST NILE VIRUS SURVEILLANCE

Raptors are a target sentinel species for West Nile virus (WNV) because many are susceptible to WNV disease, they are easily sighted because of their large size, and they often occupy territories near human settlements. Sick and dead raptors accumulate at raptor and wildlife rehabilitation clinics. However, investigations into species selection and specimen type for efficient detection of WNV are lacking. Accordingly, we evaluated dead raptors from north-central Colorado, US and southeast Wyoming, US over a 4-yr period. Nonvascular mature feathers ("quill"), vascular immature feathers ("pulp"), oropharyngeal swabs, cloacal swabs, and kidney samples were collected from raptor carcasses at the Rocky Mountain Raptor Program in Colorado from 2013 through 2016. We tested the samples using real-time reverse transcriptase-PCR. We found that 11% (53/482) of raptor carcasses tested positive for WNV infection. We consistently detected positive specimens during a 12-wk span between the second week of July and the third week of September across all years of the study. We detected WNV RNA most frequently in vascular feather pulp from Cooper's Hawk ( Accipiter cooperii). North American avian mortality surveillance for WNV using raptors can obviate necropsies by selecting Cooper's Hawk and Red-tailed Hawk ( Buteo jamaicensis) as sentinels and targeting feather pulp as a substrate for viral detection.

Reflectance Spectra of Peacock Feathers and the Turning Angles of Melanin Rods in Barbules

I analyzed the association between the reflectance spectra and melanin rod arrangement in barbules of the eyespot of peacock feathers. The reflectance spectra from the yellow-green feather of the eyespot indicated double peaks of 430 and 540 nm. The maximum reflectance spectrum of the blue feather was 480 nm, and that of the dark blue feather was 420 nm. The reflectance spectra from brown feathers indicated double peaks of 490 and 610 nm. Transmission electron microscopic analysis confirmed that melanin rods were arranged fanwise in the outer layer toward the barbule tips. In addition, using polarized light microscope, I attempted to determine whether the turning angles of melanin rods in the barbules reflected different colors. The turning angle of the polarizing axis of the barbules was supported by that of the melanin rods, observed using transmission electron microscopic images. To compare the turning angle of melanin rods in the respective barbules, I calculated the opening width of the fanwise melanin rods by dividing the width of the barbules by the turning angle of the polarizing axis of barbules and obtained a positive correlation between the reflectance spectra and opening width of the fanwise melanin rods. Moreover, the widely spreading reflection from the barbules may occur because of the fanwise melanin rod arrangement.

Quantifying the dynamic wing morphing of hovering hummingbird

Animal wings are lightweight and flexible; hence, during flapping flight their shapes change. It has been known that such dynamic wing morphing reduces aerodynamic cost in insects, but the consequences in vertebrate flyers, particularly birds, are not well understood. We have developed a method to reconstruct a three-dimensional wing model of a bird from the wing outline and the feather shafts (rachides). The morphological and kinematic parameters can be obtained using the wing model, and the numerical or mechanical simulations may also be carried out. To test the effectiveness of the method, we recorded the hovering flight of a hummingbird (Amazilia amazilia) using high-speed cameras and reconstructed the right wing. The wing shape varied substantially within a stroke cycle. Specifically, the maximum and minimum wing areas differed by 18%, presumably due to feather sliding; the wing was bent near the wrist joint, towards the upward direction and opposite to the stroke direction; positive upward camber and the 'washout' twist (monotonic decrease in the angle of incidence from the proximal to distal wing) were observed during both half-strokes; the spanwise distribution of the twist was uniform during downstroke, but an abrupt increase near the wrist joint was found during upstroke.

Avian gametologs as molecular tags for sex identification in birds of prey of Iran

Global environmental change and rapid destruction of natural habitats necessitate the conservation of endangered and threatened birds of prey. Recently, molecular sex identification methods based on amplification of introns of chromodomain-helicase DNA binding protein1 (CHD1) have provided valuable tools for ecological study and conservation breeding programs of birds. These methods employ a primer pair flanking an intron which varies considerably in length between the avian gametologs CHD1Z and CHD1W. Herein, we test the applicability of CHD1Z and CHD1W as universal tags for molecular sex identification in birds of prey of Iran. We showed successful sex identification in 22 species of birds of prey using feathers as the source of DNA. The results suggest that the regions of CHD1W and CHD1Z amplified in this study are conserved among most of Falconiformes, enabling accurate sex identification in birds of prey.

Features of owl wings that promote silent flight

Owls are an order of birds of prey that are known for the development of a silent flight. We review here the morphological adaptations of owls leading to silent flight and discuss also aerodynamic properties of owl wings. We start with early observations (until 2005), and then turn to recent advances. The large wings of these birds, resulting in low wing loading and a low aspect ratio, contribute to noise reduction by allowing slow flight. The serrations on the leading edge of the wing and the velvet-like surface have an effect on noise reduction and also lead to an improvement of aerodynamic performance. The fringes at the inner feather vanes reduce noise by gliding into the grooves at the lower wing surface that are formed by barb shafts. The fringed trailing edge of the wing has been shown to reduce trailing edge noise. These adaptations to silent flight have been an inspiration for biologists and engineers for the development of devices with reduced noise production. Today several biomimetic applications such as a serrated pantograph or a fringed ventilator are available. Finally, we discuss unresolved questions and possible future directions.