Avian Feathers Research Articles

Feathers of Bulbulcus ibis (L.) as a non-destructive biomonitoring tool for assessment of lead pollution: A case study from various severely contaminated wetland habitats

Present study aims to determine the lead (Pb) concentrations in the feather samples of cattle egret (Bulbulcus ibis) found in different contaminated wetland habitats present in the state Odisha, India. This study also focused on the heavy metal concentrations of top layer soil and on the level of metal accumulation in prey samples (i.e. small fishes) preferred by cattle egrets for explaining the level of amplification of Pb in different polluted wetland habitats. Moreover, reasons behind the variations of Pb concentrations within the sampled wetland habitats are explained. Feathers, Prey samples and sediments from their foraging habitats were collected from eight different heronries. Determination of Pb concentrations in samples has undergone acid digestion followed by elemental analysis (i.e. Pb) in Atomic Absorption Spectrophotometer (AAS). The results indicated that Pb concentration was varied significantly in soil (15.13-56.26µg/g), Prey (0.21-55.76µg/g) and feathers (5.6-49.86µg/g) in different sites. The highest concentration was found at Hirakud in soil and prey. However, feather samples showed the highest concentrations of lead in Talcher may be due to the mining activities in and around the sampling location. Present study found the positive correlation (p<0.05) between soil, prey and feather samples of cattle egret among the eight sampling locations may be due to many of the mining, industrial and anthropogenic sources. The processes like geophagy and biomagnification may contribute to the positive correlation among the sampling habitats. Concluding this work, it might be confirmed that avian feathers can be used as non-destructive biomonitoring tool for assessment of the heavy metal contamination level in various segments of different ecosystems. Hence, based on the results of the study, the environmental management plan could be suggested and implemented for better conservation of the avian fauna.

Gust response of kite plane with the flexible wings inspired by avian feathers

Gust response of kite plane with the flexible wings inspired by avian feathers

Conserved gene signalling and a derived patterning mechanism underlie the development of avian footpad scales

BackgroundVertebrates possess a diverse range of integumentary epithelial appendages, including scales, feathers and hair. These structures share extensive early developmental homology, as they mostly originate from a conserved anatomical placode. In the context of avian epithelial appendages, feathers and scutate scales are known to develop from an anatomical placode. However, our understanding of avian reticulate (footpad) scale development remains unclear.ResultsHere, we demonstrate that reticulate scales develop from restricted circular domains of thickened epithelium, with localised conserved gene expression in both the epithelium and underlying mesenchyme. These domains constitute either anatomical placodes, or circular initiatory fields (comparable to the avian feather tract). Subsequent patterning of reticulate scales is consistent with reaction–diffusion (RD) simulation, whereby this primary domain subdivides into smaller secondary units, which produce individual scales. In contrast, the footpad scales of a squamate model (the bearded dragon, Pogona vitticeps) develop synchronously across the ventral footpad surface.ConclusionsWidely conserved gene signalling underlies the initial development of avian reticulate scales. However, their subsequent patterning is distinct from the footpad scale patterning of a squamate model, and the feather and scutate scale patterning of birds. Therefore, we suggest reticulate scales are a comparatively derived epithelial appendage, patterned through a modified RD system.

Bioinspired avian feather designs.

Avian flight feathers have developed, through evolution, an intricate architecture with multi-functional structures that are essential for flight. These lightweight and resilient appendages motivate the invention of bioinspired designs. Here we fabricate various structures inspired by significant concepts identified in the feather vane and shaft. Bioinspired prototypes based on the feather vane's unique adhesive mechanism and directional permeability are explored, and feather-shaft inspired designs motivated by the highly ordered hierarchical fiber-matrix structure in the feather are fabricated. The exquisite architecture of the rachis, consisting of a hollow tube filled with foam, is simulated in a bioinspired design that demonstrates the synergy of the two components in enhancing the flexural strength. These structures provide an enhanced understanding of the mechanisms operating in feathers and suggest highly efficient solutions which can contribute to creating innovative materials inspired by the feather.

Characterization of melanosomes involved in the production of non-iridescent structural feather colours and their detection in the fossil record.

Non-iridescent structural colour in avian feathers is produced by coherent light scattering through quasi-ordered nanocavities in the keratin cortex of the barbs. To absorb unscattered light, melanosomes form a basal layer underneath the nanocavities. It has been shown that throughout Aves, melanosome morphology reflects broad categories of melanin-based coloration, as well as iridescence, allowing identification of palaeocolours in exceptionally preserved fossils. However, no studies have yet investigated the morphology of melanosomes in non-iridescent structural colour. Here, we analyse a wide sample of melanosomes from feathers that express non-iridescent structural colour from a phylogenetically broad range of extant avians to describe their morphology and compare them with other avian melanosome categories. We find that investigated melanosomes are typically wide (approx. 300 nm) and long (approx. 1400 nm), distinct from melanosomes found in black, brown and iridescent feathers, but overlapping significantly with melanosomes from grey feathers. This may suggest a developmental, and perhaps evolutionary, relationship between grey coloration and non-iridescent structural colours. We show that through analyses of fossil melanosomes, melanosomes indicative of non-iridescent structural colour can be predicted in an Eocene stem group roller ( Eocoracias: Coraciiformes) and with phylogenetic comparative methods the likely hue can be surmised. The overlap between melanosomes from grey and non-iridescent structurally coloured feathers complicates their distinction in fossil samples where keratin does not preserve. However, the abundance of grey coloration relative to non-iridescent structural coloration makes the former a more likely occurrence except in phylogenetically bracketed specimens like the specimen of Eocoracias studied here.

Unveiled feather microcosm: feather microbiota of passerine birds is closely associated with host species identity and bacteriocin-producing bacteria

The functional relevance of microbiota is a key aspect for understanding host–microbiota interactions. Mammalian skin harbours a complex consortium of beneficial microorganisms known to provide health and immune-boosting advantages. As yet, however, little is known about functional microbial communities on avian feathers, including their co-evolution with the host and factors determining feather microbiota (FM) diversity. Using 16S rRNA profiling, we investigated how host species identity, phylogeny and geographic origin determine FM in free-living passerine birds. Moreover, we estimated the relative abundance of bacteriocin-producing bacteria (BPB) and keratinolytic feather damaging bacteria (FDB) and evaluated the ability of BPB to affect FM diversity and relative abundance of FDB. Host species identity was associated with feather bacterial communities more strongly than host geographic origin. FM functional properties differed in terms of estimated BPB and FDB relative abundance, with both showing interspecific variation. FM diversity was negatively associated with BPB relative abundance across species, whereas BPB and FDB relative abundance was positively correlated. This study provides the first thorough evaluation of antimicrobial peptides-producing bacterial communities inhabiting the feather integument, including their likely potential to mediate niche-competition and to be associated with functional species-specific feather microbiota in avian hosts.

Duplications in Corneous Beta Protein Genes and the Evolution of Gecko Adhesion.

Corneous proteins are an important component of the tetrapod integument. Duplication and diversification of keratins and associated proteins are linked with the origin of most novel integumentary structures like mammalian hair, avian feathers, and scutes covering turtle shells. Accordingly, the loss of integumentary structures often coincides with the loss of genes encoding keratin and associated proteins. For example, many hair keratins in dolphins and whales have become pseudogenes. The adhesive setae of geckos and anoles are composed of both intermediate filament keratins (IF-keratins, formerly known as alpha-keratins) and corneous beta-proteins (CBPs, formerly known as beta-keratins) and recent whole genome assemblies of two gecko species and an anole uncovered duplications in seta-specific CBPs in each of these lineages. While anoles evolved adhesive toepads just once, there are two competing hypotheses about the origin(s) of digital adhesion in geckos involving either a single origin or multiple origins. Using data from three published gecko genomes, I examine CBP gene evolution in geckos and find support for a hypothesis where CBP gene duplications are associated with the repeated evolution of digital adhesion. Although these results are preliminary, I discuss how additional gecko genome assemblies, combined with phylogenies of keratin and associated protein genes and gene duplication models, can provide rigorous tests of several hypotheses related to gecko CBP evolution. This includes a taxon sampling strategy for sequencing and assembly of gecko genomes that could help resolve competing hypotheses surrounding the origin(s) of digital adhesion.

From Scale to Spine: Evolution and Developmental Diversity of Skin Spines in Pufferfishes

Teleost fishes develop a remarkable variety of skin ornaments. However, the developmental basis of these structures is poorly understood. The teleost order Tetraodontiformes includes diverse fishes such as the ocean sunfishes, triggerfishes and pufferfishes, which exhibit a vast assortment of scale derivatives. Pufferfishes and porcupine fishes possess some of the most extreme scale derivatives, dermal spines, which are erected during their characteristic puffing behavior. Here, we focus on pufferfishes and demonstrate that the spines develop through conserved gene interactions that underlie skin appendage formation throughout other vertebrates, including avian feathers and mammalian hair. Pufferfish spine development retains the conserved role of the EDA (ectodysplasin) signaling pathway, suggesting that EDA is an important molecule/pathway for the development of diverse vertebrate skin appendages, including these modified scale-less spines of the pufferfish lineage. Further modification of genetic signaling from both CRISPR-Cas9 and small molecule inhibition can lead to both loss or reduction of spine coverage in pufferfish, providing a mechanism for skin appendage diversification observed in the extant clade of pufferfishes (Tetraodontidae). Dermal spines are unique scale-derivatives that evolved through conserved gene network modification. In pufferfish they exhibit broad variation in coverage, enabling adaptation to diverse ecological niches.

I see your false colours: how artificial stimuli appear to different animal viewers.

The use of artificially coloured stimuli, especially to test hypotheses about sexual selection and anti-predator defence, has been common in behavioural ecology since the pioneering work of Tinbergen. To investigate the effects of colour on animal behaviour, many researchers use paints, markers and dyes to modify existing colours or to add colour to synthetic models. Because colour perception varies widely across species, it is critical to account for the signal receiver's vision when performing colour manipulations. To explore this, we applied 26 typical coloration products to different types of avian feathers. Next, we measured the artificially coloured feathers using two complementary techniques-spectrophotometry and digital ultraviolet--visible photography-and modelled their appearance to mammalian dichromats (ferret, dog), trichromats (honeybee, human) and avian tetrachromats (hummingbird, blue tit). Overall, artificial colours can have dramatic and sometimes unexpected effects on the reflectance properties of feathers, often differing based on feather type. The degree to which an artificial colour differs from the original colour greatly depends on an animal's visual system. 'White' paint to a human is not 'white' to a honeybee or blue tit. Based on our analysis, we offer practical guidelines for reducing the risk of introducing unintended effects when using artificial colours in behavioural experiments.

Facile Fabrication of Amorphous Photonic Structures with Non-Iridescent and Highly-Stable Structural Color on Textile Substrates.

Amorphous photonic structures with non-iridescent and highly-stable structural color were fabricated via a simple one-step spray-coating technique. With this strategy, the obtained films on textile substrates presented short-ordered and amorphous photonic structures (APSs) similar to the amorphous nanostructures of avian feathers. The structural color presented the same hue when viewed at different angles and could be well controlled by varying the diameters of the SiO2 nanospheres. The prepared fabrics with structural color exhibited high color stability due to stability in both the assembled physical structure and the refractive index. The high stability of the assembled physical structure was attributed to the cementing effect of Poly(methylmethacrylate-butylacrylate) P(MMA-BA) existing between textile substrate and SiO2 nanospheres and among SiO2 nanospheres, while the high stability in the refractive index was contributed by the liquid-resistance achieved by both the surface roughness and the low-surface-energy of the as-sprayed APSs. With the resistances to external forces and liquid invasion, the non-iridescent brilliant structural color of the as-prepared fabrics could be kept steady. In this study, an approach of fabricating APSs with non-iridescent and stable structural color was established to enhance its potential application in structural coloration of textiles, and other color-related smart textiles.

Bristle Scale As a Predecessor of Protofeather and Feather

The bristle scale is a skin appendage recognized in the ornithiscian dinosaurs Daurosaurus olovus and Kulindapteryx ukureica from the Kulinda locality (Transbaikalia, Russia). Morphologically, the bristle scale is a horn plate immersed in the dermis, with strands (bristles) diverging from its external edge. It is assumed that the filamentous protofeather of dinosaurs is the monobristle variant of the bristle scale and avian feather results from its tubular spatial modification. The bristle scale is considered to be intermediate between the reptilian scale and avian feather.

Comprehensive molecular and cellular studies suggest avian scutate scales are secondarily derived from feathers, and more distant from reptilian scales

Amniote skin appendages such as feathers, hairs and scales, provide thermoregulation, physical protection and display different color patterns to attract a mate or frighten an adversary. A long-standing question is whether “reptile scale” and “avian leg scales” are of the same origin. Understanding the relation between avian feathers, avian scales and reptilian scales will enhance our understanding of skin appendage evolution. We compared the molecular and cellular profiles in chicken feather, chicken scales and alligator scales and found that chicken scutate scales are similar to chicken feathers in morphogenesis at the early placode stage. When we compared the expression of the recently identified feather-specific genes and scale-specific genes in these skin appendages, we found that at the molecular level alligator scales are significantly different from both chicken feathers and chicken scales. Furthermore, we identified a similarly diffuse putative stem cell niche in morphologically similar chicken and alligator scales. These putative stem cells participate in alligator scale regeneration. In contrast, avian feathers have a more condensed stem cell niche, which may be responsible for cycling. Thus, our results suggest that chicken and alligator scales formed independently through convergent evolution.

An ancient Turing-like patterning mechanism regulates skin denticle development in sharks.

Vertebrates have a vast array of epithelial appendages, including scales, feathers, and hair. The developmental patterning of these diverse structures can be theoretically explained by Alan Turing's reaction-diffusion system. However, the role of this system in epithelial appendage patterning of early diverging lineages (compared to tetrapods), such as the cartilaginous fishes, is poorly understood. We investigate patterning of the unique tooth-like skin denticles of sharks, which closely relates to their hydrodynamic and protective functions. We demonstrate through simulation models that a Turing-like mechanism can explain shark denticle patterning and verify this system using gene expression analysis and gene pathway inhibition experiments. This mechanism bears remarkable similarity to avian feather patterning, suggesting deep homology of the system. We propose that a diverse range of vertebrate appendages, from shark denticles to avian feathers and mammalian hair, use this ancient and conserved system, with slight genetic modulation accounting for broad variations in patterning.

Humboldt penguins' feathers as bioindicators of metal exposure

Avian feathers have the potential to accumulate trace elements originating from contaminated food and polluted environments. In fact, in feathers, metals bind to keratin, a sulphur-containing protein for which several metals have a strong affinity. Here, the concentrations of 18 essential and non-essential elements were investigated in a Humboldt penguin (Spheniscus humboldti) colony housed at the Acquario di Cattolica (Italy). This species is listed as vulnerable in the Red List of the International Union for Conservation of Nature. According to the literature, there is usually a link between metal levels in the diet of birds and levels detected in their feathers. Thus, metals were also determined in the penguins' food (capelin, Mallotus villosus). We hypothesize that the controlled conditions in which birds are kept in captivity, and the homogeneous diet that they follow could allow a better understanding of metal bioaccumulation (such as mercury) or bio-dilution (such as arsenic) in the marine food chain, indicated by penguins' feathers.Moreover, comparisons with our previous investigations performed on an ex-situ African penguin (Spheniscus demersus) colony suggest that penguins living indoors have lower body burden of metals than those living outdoors. Indeed, environmental contaminants usually found in areas subjected to anthropogenic impact, where zoos and aquaria are often located, are not accumulated to levels of concern.

Comparative Analysis of Epidermal Differentiation Genes of Crocodilians Suggests New Models for the Evolutionary Origin of Avian Feather Proteins

The epidermis of amniotes forms a protective barrier against the environment and the differentiation program of keratinocytes, the main cell type in the epidermis, has undergone specific alterations in the course of adaptation of amniotes to a broad variety of environments and lifestyles. The epidermal differentiation complex (EDC) is a cluster of genes expressed at late stages of keratinocyte differentiation in both sauropsids and mammals. In the present study, we identified and analyzed the crocodilian equivalent of the EDC. The gene complement of the EDC of both the American alligator and the saltwater crocodile were determined by comparative genomics, de novo gene prediction and identification of EDC transcripts in published transcriptome data. We found that crocodilians have an organization of the EDC similar to that of their closest living relatives, the birds, with which they form the clade Archosauria. Notable differences include the specific expansion of a subfamily of EDC genes in crocodilians and the loss of distinct ancestral EDC genes in birds. Identification and comparative analysis of crocodilian orthologs of avian feather proteins suggest that the latter evolved by cooption and sequence modification of ancestral EDC genes, and that the amplification of an internal highly cysteine-enriched amino acid sequence motif gave rise to the feather component epidermal differentiation cysteine-rich protein in the avian lineage. Thus, sequence diversification of EDC genes contributed to the evolutionary divergence of the crocodilian and avian integuments.

Development of highly robust wing inspired by avian feathers

Development of highly robust wing inspired by avian feathers

Multiple Regulatory Modules Are Required for Scale-to-Feather Conversion.

The origin of feathers is an important question in Evo-Devo studies, with the eventual evolution of vaned feathers which are aerodynamic, allowing feathered dinosaurs and early birds to fly and venture into new ecological niches. Studying how feathers and scales are developmentally specified provides insight into how a new organ may evolve. We identified feather-associated genes using genomic analyses. The candidate genes were tested by expressing them in chicken and alligator scale forming regions. Ectopic expression of these genes induced intermediate morphotypes between scales and feathers which revealed several major morphogenetic events along this path: Localized growth zone formation, follicle invagination, epithelial branching, feather keratin differentiation, and dermal papilla formation. In addition to molecules known to induce feathers on scales (retinoic acid, β-catenin), we identified novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce one or more regulatory modules guiding these morphogenetic events. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, whereas others exhibit characteristics of modern avian feathers. We propose these morpho-regulatory modules were used to diversify archosaur scales and to initiate feather evolution. The regulatory combination and hierarchical integration may have led to the formation of extant feather forms. Our study highlights the importance of integrating discoveries between developmental biology and paleontology.

Biological monitoring of exposure to ambient lead and cadmium using avian feathers: A study from Northern India

ABSTRACTBiological monitoring of exposure to ambient environmental lead and cadmium was performed using feathers of 26 species of birds native to Western Uttar Pradesh in Northern India. The rationale of this study was to address three questions. First, is there any avian species that can be treated as a suitable bioindicator of lead or cadmium present in the environment? Second, do the birds selectively accumulate lead and cadmium in their feathers and exhibit interspecies variation? Third, is there any threat to endangered species of this region from metal pollution? Average concentration of lead in the feathers of selected birds ranged from 3.40 µg/g in parrot to 301.6 µg/g in golden pheasant, whereas cadmium concentration was higher ranging from 40.20 µg/g in red crow to 450 µg/g in blue macaw. A comparison of results made through ANOVA revealed a significant difference in the concentration of lead (df = 25; F = 3965.54) and cadmium (df = 25; F = 8537.27) in their feathers. We hypothesize that feathers of synanthropic birds may be treated as suitable noninvasive tool to monitor the ambient environmental contamination by lead and cadmium. Their accumulation in endangered birds may lead to population decline causing serious ecological disturbances in the region.

Technical note: Induction of pluripotent stem cell-like cells from chicken feather follicle cells.

Pluripotent stem cells including embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are regarded as representative tools for conservation of animal genetic resources. Although ESC have been established from chicken, it is very difficult to obtain enough embryos for isolation of stem cells for avian conservation in most wild birds. Therefore, the high feasibility of obtaining the pluripotent cell is most important in avian conservation studies. In this study, we generated induced pluripotent stem cell-like cells (iPSLC) from avian Feather Follicular cells (FFC). Avian FFC are one of the most easily accessible cell sources in most avian species, and their reprogramming into pluripotent stem cells can be an alternative system for preservation of avian species. Intriguingly, FFC had mesenchymal stromal cells (MSC)-like characteristics with regard to gene expression, protein expression, and adipocyte differentiation. Subsequently, we attempted to generate iPSLC from FFC using retroviral vectors. The FFC-iPSLC can proliferate with the stem pluripotent property and differentiate into several types of cells in vitro. Our results suggest that chicken FFC are an alternative cell source for avian cell reprogramming into pluripotent stem cells. This experimental strategy should be useful for conservation and restoration of endangered or high-value avian species without sacrificing embryos.

Comparative aerodynamics of synthetic badminton shuttlecocks

Badminton synthetic shuttlecocks are known to have significantly different aerodynamic behaviours compared to feathered shuttlecocks due to the difference in designs and use of materials. Given the fragility of avian feathers used for feathered shuttlecocks and the constantly increasing cost of purchase, the interest to assess the current synthetic shuttlecock design as a feasible alternative has re-emerged. The single-piece injection-moulded synthetic shuttlecock has been the mainstream design for the past 50 years; however, little evidence has supported that the design mimics the aerodynamics of feathered shuttlecocks. Recently, a two-part skirt design has emerged proclaiming to have surpassed its synthetic predecessor in regard to matching the aerodynamics of feathered shuttlecocks. In the current study, two different synthetic designs (injection-moulded vs two-part skirt) were benchmarked against a feathered shuttlecock. A wind tunnel test was conducted between 30 and 145 km/h. The drag coefficients of both synthetic shuttlecocks were similar to the feathered shuttlecock up to 105 km/h. Thereafter, the drag coefficient of the injection-moulded design dropped from 0.62 to 0.5 and showing no signs of levelling at speeds over 105 km/h, while the coefficient for two-part skirt design stabilised at approximately 0.55. It was concluded that the two-part skirt design better mimicked the aerodynamics of the feathered shuttlecock.