Multilayer thin-film produces recurrent evolution of iridescence in mammals.

Iridescent coloration is a vibrant structural colour that is widespread in nature, but in mammals is thought to be limited. Although multiple rodent and Eulipotyphlan species have been anecdotally described as iridescent, empirical evidence outside of the Chrysochloridae (golden mole) family is lacking. As iridescence in golden moles is created through a thin-film mechanism from a compressed cuticle structure, and the structure of hair is highly conserved, we expect iridescence to be present, and produced by the same mechanism, in mammals that share similar hair properties.

Modular design of biomimetic electrospun keratin composites for tunable gaseous sorption inspired by reptile eggshells.

Biomimicry, the replication of natural structures, is an emerging strategy in materials engineering for developing advanced functional materials. Reptile eggshells serve as compelling models for tunable bioinspired material design due to their diversity in forms and functions. This study presents a modular approach to designing keratin-based composites with customizable vapor sorption behavior.

Now you see me, now you don't.

Nanostructured reflecting plates in squid cells enable a rapid switch between colored and near-transparent states.

Convergence in biomineralization patterns across animal eggshells.

Shelled eggs are key components of animal reproduction on land, evolving independently in distant lineages of terrestrial animals including nematodes, gastropods, annelids, arthropods and chordates. They perform critical functions such as the exchange of gases between embryo and the environment, desiccation avoidance and protection from harmful radiation, microbial infection and mechanical damage. A core mechanism behind eggshell multifunctionality is the incorporation of biominerals (mainly calcium carbonate and calcium phosphate) into the shell.

Habitat openness and squamate color evolution over deep time.

While the ecological roles of colored integument have been extensively studied, what regulates global patterns of color variation remains poorly understood. Here, using a global dataset of 1249 squamates, we evaluate whether and how six key eco-environmental variables and their interactions shaped the evolutionary history of their coloration. We show that only habitat openness consistently associates with brightness evolution, with brighter integuments favored in open habitats, possibly for enhanced heat reflection.

Mesozoic mammaliaforms illuminate the origins of pelage coloration.

Pelage coloration, which serves numerous functions, is crucial to the evolution of behavior, physiology, and habitat preferences of mammals. However, little is known about the coloration of Mesozoic mammaliaforms that coevolved with dinosaurs. In this study, we used a dataset of melanosome (melanin-containing organelle) morphology and quantitatively measured hair colors from 116 extant mammals to reliably reconstruct the coloration of six Mesozoic mammaliaforms, including a previously undescribed euharamiyidan.

Colorful photothermal photonic crystal cotton fabric based on melanin-like polycaffeic acid nanoparticles.

Photothermal materials have been extensively researched and utilized owing to their exceptional energy conversion capabilities. However, developing dual-functional materials with both vivid coloration and efficient photothermal performance remains a significant challenge, primarily because most photothermal materials have an undesirable black appearance. Herein, colorful photothermal polycaffeic photonic crystal (PCfA PC) cotton fabric was successfully created by assembling melanin-like polycaffeic acid nanoparticles (PCfA NPs) with adjustable size and high monodispersity.

Transitions between colour mechanisms affect speciation dynamics and range distributions of birds.

Several ecogeographical 'rules' have been proposed to explain colour variation at broad spatial and phylogenetic scales but these rarely consider whether colours are based on pigments or structural colours. However, mechanism can have profound effects on the function and evolution of colours. Here, we combine geographic information, climate data and colour mechanism at broad phylogenetic (9,409 species) and spatial scales (global) to determine how transitions between pigmentary and structural colours influence speciation dynamics and range distributions in birds.

The function and consequences of fluorescence in tetrapods.

Fluorescence, the optical phenomenon whereby short-wavelength light is absorbed and emitted at longer wavelengths, has been widely described in aquatic habitats, in both invertebrates and fish. Recent years have seen a stream of articles reporting fluorescence, ranging from frogs, platypus, to even fully terrestrial organisms such as flying squirrels, often explicitly or implicitly linking the presence of fluorescence with sexual selection and communication. However, many of these studies fail to consider the physiological requirements of evolutionary stable signaling systems, the environmental dependence of perception, or the possible adaptive role of fluorescent coloration in a noncommunicative context.

Interactions of Melanin with Electromagnetic Radiation: From Fundamentals to Applications.

Melanin, especially integumentary melanin, interacts in numerous ways with electromagnetic radiation, leading to a set of critical functions, including radiation protection, UV-protection, pigmentary and structural color productions, and thermoregulation. By harnessing these functions, melanin and melanin-like materials can be widely applied to diverse applications with extraordinary performance. Here we provide a unified overview of the melanin family (all melanin and melanin-like materials) and their interactions with the complete electromagnetic radiation spectrum (X-ray, Gamma-ray, UV, visible, near-infrared), which until now has been absent from the literature and is needed to establish a solid fundamental base to facilitate their future investigation and development.

Hydric Environment and Chemical Composition Shape Non-avian Reptile Eggshell Absorption.

The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution.

The Evolution of Multiple Color Mechanisms Is Correlated with Diversification in Sunbirds (Nectariniidae).

How and why certain groups become speciose is a key question in evolutionary biology. Novel traits that enable diversification by opening new ecological niches are likely important mechanisms. However, ornamental traits can also promote diversification by opening up novel sensory niches and thereby creating novel inter-specific interactions.

Back in black: melanin-rich skin colour associated with increased net diversification rates in birds.

Evolutionary biologists have long been interested in understanding the factors that promote diversification in organisms, often focussing on distinct and/or conspicuous phenotypes with direct effects on natural or sexual selection such as body size and plumage coloration. However, multiple traits that potentially influence net diversification are not conspicuous and/or might be concealed. One such trait, the dark, melanin-rich skin concealed beneath the feathers, evolved more than 100 times during avian evolution, frequently in association with white feathers on the crown and UV-rich environments, suggesting that it is a UV-photoprotective adaptation.

Body size and substrate use affect ventral, but not dorsal, brightness evolution in lizards.

Substrate properties can affect the thermal balance of organisms, and the colored integument, alongside other factors, may influence heat transfer via differential absorption and reflection. Dark coloration may lead to higher heat absorption and could be advantageous when substrates are cool (and vice versa for bright coloration), but these effects are rarely investigated. Here, we examined the effect of substrate reflectance, specific heat capacity (cp), and body size on the dorso-ventral brightness using 276 samples from 12 species of cordylid lizards distributed across 26 sites in South Africa.

Biomimetic pheomelanin to unravel the electronic, molecular and supramolecular structure of the natural product.

Herein, we investigate synthetic routes to a close mimic of natural pheomelanin. Three different oxidative polymerization routes were attempted to generate synthetic pheomelanin, each giving rise to structurally dissimilar materials. Among them, the route employing 5-cysteinyl-dihydroxyphenylalanine (5-CD) as a monomer was verified as a close analogue of extracted pheomelanin from humans and birds.

Hydrophobic Melanin via Post-Synthetic Modification for Controlled Self-Assembly.

Allomelanin is a class of nitrogen-free melanin mostly found in fungi and, like all naturally occurring melanins, is hydrophilic. Herein, we develop a facile method to modify synthetic hydrophilic allomelanin to yield hydrophobic derivatives through post-synthetic modifications. Amine-functionalized molecules of various kinds can be conjugated to allomelanin nanoparticles under mild conditions with high loading efficiencies.

A combination of red structural and pigmentary coloration in the eyespot of a copepod.

While the specific mechanisms of colour production in biological systems are diverse, the mechanics of colour production are straightforward and universal. Colour is produced through the selective absorption of light by pigments, the scattering of light by nanostructures or a combination of both. When copepods were fed a carotenoid-limited diet of yeast, their orange-red body coloration became faint, but their eyespots remained unexpectedly bright red.

Pterosaur melanosomes support signalling functions for early feathers.

Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers. New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic, but the homology of these pterosaur structures with feathers is controversial. Reports of pterosaur feathers with homogeneous ovoid melanosome geometries suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation.

Enhanced photothermal absorption in iridescent feathers.

The diverse colours of bird feathers are produced by both pigments and nanostructures, and can have substantial thermal consequences. This is because reflectance, transmittance and absorption of differently coloured tissues affect the heat loads acquired from solar radiation. Using reflectance measurements and heating experiments on sunbird museum specimens, we tested the hypothesis that colour and their colour producing mechanisms affect feather surface heating and the heat transferred to skin level.

The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency.

Seabirds have evolved numerous adaptations that allow them to thrive under hostile conditions. Many seabirds share similar colour patterns, often with dark wings, suggesting that their coloration might be adaptive. Interestingly, these darker wings become hotter when birds fly under high solar irradiance, and previous studies on aerofoils have provided evidence that aerofoil surface heating can affect the ratio between lift and drag, i.

Morphogenesis of Iridescent Feathers in Anna's Hummingbird Calypte anna.

Color is a phenotypic trait of utmost importance, particularly in birds, which are known for their diverse color signals and color-producing mechanisms including pigment-based colors, light scattering from nanostructured feather tissues and combinations thereof. Bright iridescent plumage colors of hummingbirds are caused by light scattering by an organized array of flattened, pigment organelles, containing air-filled vesicles, called melanosomes. These hollow platelets are organized in multilayer arrays that contain numerous sharp air/melanin refractive index interfaces, producing brilliant iridescent colors.