Explore the vast range of titles available.

The rational of conservation and sustainable use of indigenous chicken (IC) resources requires their morphobiometrical characterisation. This study morphobiometrically characterised the IC ecotypes in Rwanda. The morphological features and zoometric measurement data were randomly collected on 1670 mature IC of both sexes from five ecotypes of Rwanda. The nonparametric Kruskal–Wallis and Mann–Whitney U test were used in evaluating the effect of ecotypes on the qualitative morphological variables. Zoometric measurements were analysed with the PROC GLM of SAS. The findings showed that the feather morphology and distribution were mainly normal (98.3 and 84.40%, respectively) while feather colour was dominated with multicoloured (38.10%). The majority of the birds had red earlobe (49.20%), yellow shanks (53.80%) and single comb-type (71.70%). These parameters were different (p < 0.05) between the ecotypes. Bodyweight and linear body measurements were highly different (P < 0.001) between ecotypes. Differences associated with sex (P < 0.001) were observed in body weight and linear body measurements. The interaction between ecotype and sex significantly (P < 0.001) influenced body weight, body length, shank length, comb length, comb height, wattle length, chest circumference, neck length and wingspan. The IC ecotypes in Rwanda were found to be diverse morphobiometrically both in quantitative and qualitative traits. These variations provide a foundation for classification of the chicken into breeds.

Feathers are important economic products. Anser cygnoide (AC) is superior in reproduction, growth and feather quality, while Anser anser (AA) has an advantage in feather yield. Understanding the development of feather follicles facilitates deliberate crossbreeding. Here, we compared feather follicles morphogenesis between AC and AA. Feathers and dorsal skin were sampled at multiple embryonic days to investigate feather phenotypes, feather follicle morphology and the expression of hub molecules (FZD4, β-catenin, LEF1, TCF4 and c-Myc) in the Wnt signalling pathway. We found a marked difference in plumage colour between the two breeds. Feather colour in AA has undergone a 'black dorsum' stage and cavity formation in AC was earlier. Furthermore, different trends in molecular hub expression helped explain the phenotypical and morphological differences: the upregulated Wnt signals in AC at E12 and/or E15, as well as in AA at E18, were associated with early epidermal placode formation and cavity formation in AC, also, related to the development of the secondary feather follicles and 'black dorsum' in AA. Summarily, breed-specific expression patterns of Wnt signalling pathway between AC and AA might participate in the shaping of breed-specific feather follicles morphogenesis and feather phenotypes. This work provides references for feather follicles development in geese.

Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05–0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display. Physical structure is known to contribute to the appearance of bird plumage through structural color and specular reflection. Here, McCoy, Feo, and colleagues demonstrate how a third mechanism, structural absorption, leads to low reflectance and super black color in birds of paradise feathers.

Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur Anchiornis were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur–bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.

The spacing of hair in mammals and feathers in birds is one of the most apparent morphological features of the skin. This pattern arises when uniform fields of progenitor cells diversify their molecular fate while adopting higher-order structure. Using the nascent skin of the developing chicken embryo as a model system, we find that morphological and molecular symmetries are simultaneously broken by an emergent process of cellular self-organization. The key initiators of heterogeneity are dermal progenitors, which spontaneously aggregate through contractility-driven cellular pulling. Concurrently, this dermal cell aggregation triggers the mechanosensitive activation of β-catenin in adjacent epidermal cells, initiating the follicle gene expression program. Taken together, this mechanism provides a means of integrating mechanical and molecular perspectives of organ formation.

Feathers are arranged in a precise pattern in avian skin. They first arise during development in a row along the dorsal midline, with rows of new feather buds added sequentially in a spreading wave. We show that the patterning of feathers relies on coupled fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) signalling together with mesenchymal cell movement, acting in a coordinated reaction-diffusion-taxis system. This periodic patterning system is partly mechanochemical, with mechanical-chemical integration occurring through a positive feedback loop centred on FGF20, which induces cell aggregation, mechanically compressing the epidermis to rapidly intensify FGF20 expression. The travelling wave of feather formation is imposed by expanding expression of Ectodysplasin A (EDA), which initiates the expression of FGF20. The EDA wave spreads across a mesenchymal cell density gradient, triggering pattern formation by lowering the threshold of mesenchymal cells required to begin to form a feather bud. These waves, and the precise arrangement of feather primordia, are lost in the flightless emu and ostrich, though via different developmental routes. The ostrich retains the tract arrangement characteristic of birds in general but lays down feather primordia without a wave, akin to the process of hair follicle formation in mammalian embryos. The embryonic emu skin lacks sufficient cells to enact feather formation, causing failure of tract formation, and instead the entire skin gains feather primordia through a later process. This work shows that a reaction-diffusion-taxis system, integrated with mechanical processes, generates the feather array. In flighted birds, the key role of the EDA/Ectodysplasin A receptor (EDAR) pathway in vertebrate skin patterning has been recast to activate this process in a quasi-1-dimensional manner, imposing highly ordered pattern formation.

Developmental processes extend beyond embryogenesis to support lifelong tissue adaptations. Avian feather follicles, with their resident stem cells and capacity for cyclic regeneration, provide a dynamic model for postnatal tissue remodeling. Here, we propose the Mandarin duck ( Aix galericulata ) as an ideal model to study lifelong developmental modulation, focusing on the sexually dimorphic “sail feather”—a secondary flight feather in males that undergoes seasonal transformation into a strikingly asymmetric, ornamented phenotype during the breeding season. We identified asymmetric morphogen expression in regenerating male sail feathers and used transcriptome and H3K27ac ChIP-seq to uncover male and female signaling pathways and regulatory elements. Comparative epigenomic profiling reveals enriched estrogen receptor binding motifs in females. Hormone profiling shows seasonal variation, with a marked rise in female estrogen levels preceding the mating season. These results imply Mandarin duck sail feathers integrate local morphogenetic programs, epigenetic regulation, and systemic hormonal cues to orchestrate sexually dimorphic and seasonally dynamic feather morphogenesis. This work establishes a framework for further mechanistic study of the interplay between regeneration, regional identity, and hormonal plasticity in a vertebrate integumentary system.

A recently discovered fossil belonging to the Scansoriopterygidae, a group of bizarre dinosaurs closely related to birds, represents a new scansoriopterygid species and preserves evidence of a membranous aerodynamic surface very different from a classic avian wing. Taking flight by the wrist At the base of the dinosaur lineage that eventually led to birds there is a small group of bizarre dinosaurs called scansoriopterygids. They were very small, often with long digits and are usually reconstructed as tree-dwelling lemur-like creatures. Here Xing Xu and colleagues present what is possibly the strangest scansoriopterygid so far discovered. Named Yi qi , the tiny animal, from 160 million-year-old sediments in China, has an unusual assortment of stiff filamentous feathers and also two long bony elements attached to the wrists, unlike anything seen previously in any dinosaur. These structures, resembling extraneous bones seen in a variety of tetrapods, may have supported a membrane that might have sustained gliding flight. Traces of such a membrane are preserved with the specimen. The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component 1 , 2 , 3 . Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle–Upper Jurassic period Tiaojishan Formation of Hebei Province, China 4 . Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes 5 . Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods 6 , 7 , 8 , 9 , 10 , suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds.

A new specimen of Archaeopteryx with extensive pennaceous feather preservation. Feathers prominent on latest Archaeopteryx fossil The discovery of numerous feathered dinosaurs and early birds has set the iconic 'Urvogel' (or 'first bird') Archaeopteryx in a broader context. But this venerable taxon still has the capacity to surprise. A newly discovered specimen from the Solnhofen limestone in Bavaria — only the eleventh since 1861 — shows a generous covering of feathers all over the body. Of particular note is a hindlimb covering resembling feathered 'trousers'. Analysis of feather distribution on the limbs and tail strongly suggests that pennaceous feathers — the type we are familiar with on birds today — evolved for reasons other than flight, perhaps for display. Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx 1 into context 2 , 3 , 4 , 5 , 6 and have yielded important new data on the origin and early evolution of feathers 7 . However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations 8 , 9 are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies 10 , 11 , 12 . Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.