Interactions between colour-producing mechanisms and their effects on the integumentary colour palette

Abstract

Animal integumentary coloration plays a crucial role in visual communication and camouflage, and varies extensively among and within species and populations. To understand the pressures underlying such diversity, it is essential to elucidate the mechanisms by which animals have created novel integumentary coloration. Colours can be produced by selective absorption of light by skin pigments, through light scattering by structured or unstructured tissues, or by a combination of pigments and nanostructures. In this review, we highlight our current understanding of the interactions between pigments and structural integumentary tissues and molecules. We analyse the available evidence suggesting that these combined mechanisms are capable of creating colours and optical properties unachievable by either mechanism alone, thereby effectively expanding the animal colour palette. Moreover, structural and pigmentary colour mechanisms frequently interact in unexpected and overlooked ways, suggesting that classification of colours as being of any particular type may be difficult. Finally, we discuss how these mixtures are useful for investigating the largely unknown genetic, developmental and physical processes generating phenotypic diversity.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.

Three‐dimensional soft tissue preservation revealed in the skin of a non‐avian dinosaur

“…Colouration of the skin is generally determined by melanophores and chromatophores and the structural layering of the integument (McNamara et al . ; Shawkey & D'Alba ). Chromatophores and melanophores are usually stored at the interface between the epidermis and dermis in vertebrates (Prum & Torres , ; Chang et al .…”

“…; McNamara et al . ; Shawkey & D'Alba ). The innermost layer of the skin, the subcutaneous layer, separates the integument from the rest of the body.…”

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

“…Color is a major axis of phenotypic variation, particularly in birds, which produce diverse color signals through a combination of light absorption by pigments (pigment‐based colors) and light scattering from nanostructured feather tissues composed of melanin, keratin, and air (structural colors) (Stoddard and Prum ; Shawkey and D'Alba ). In general, birds with more complex nanostructures have more variable structural colors (Maia et al.…”

It's Not a Bug, It's a Feature: Functional Materials in Insects

“…[277] Numerous recent reviews discuss the physical aspects of insect displays, [273,[277][278][279][280][281][282][283][284][285][286] as well as their function in animal communication. [275,276,287] In general, there are two main classes of animal coloration: pigmentary coloration due to the wavelength-selective light absorption by chemical dyes and structural coloration due to the interaction of incident light with ordered, quasi-ordered or disordered nanostructures causing interference. [277,288,289] Both coloration mechanisms feature unique optical properties that can combine in nontrivial ways and modulate optical properties with potential applications ranging from displays, to brilliant durable paints, to adaptive camouflage and transparent materials.…”

“…[277,288,289] Both coloration mechanisms feature unique optical properties that can combine in nontrivial ways and modulate optical properties with potential applications ranging from displays, to brilliant durable paints, to adaptive camouflage and transparent materials. [287,[290][291][292][293] Interferometric modulator displays are a low-power microelectromechanical display technology based on structural coloration, enabling full visibility in direct sunlight, unlike conventional liquid-crystal display screens. [294,295] The concept is relatively simple: each pixel in the display contains a fixed, semitransparent membrane separated a distance (air-gap) of ≈1 µm above a reflective, moveable thin-film stack.…”