A worn path summary and analysis

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a worn path summary and analysis

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Phase relationships of wavelengths scattered by two different objects (x and y) are given by the differences in the path lengths of light scattered by the first object (x: 11 and a second object (y: 22 as measured from planes perpendicular to the incident (a). Left, In constructive interference (coherent scattering two light waves (on bottom) are in phase so the combined waveform (top) is enhanced. Right, In destructive interference, two light waves (bottom) out of phase so they cancel out (top). In some groups of birds (e.g., Phasianidae, eurylaimidae, cotingidae, paradisaeidae, and Cnemophilidae sexual selection is likely responsible for the structurally colored skin of males because most species are polygynous. In other groups of birds, including Ardeidae, cariamidae, bucerotidae, ramphastidae, meliphagidae, and Monarchidae, both sexes have integumentary structural colors, suggesting that such coloration may be important in both inter- and intrasexual communication (Prum and Torres 2003). Many birds with structurally colored skin are found in rainforests. For example, nearly all species with structurally colored skin in the orders Casuariiformes, galliformes, Opisthocomiformes, cuculiformes, Trogoniformes, coraciiformes, piciformes, and Passeriformes occur in tropical forests. The quality of ambient light in tropical forest habitats may favor the evolution of communication signals in the shorter wavelength portion of the visible spectrum (blue and green) and, if so, selection might favor structural colors because vertebrates, including birds, have no pigments that generate.

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In bird skin, this light-absorbing layer consists of a thick layer of melanin granules (melanosomes; Figure 7). Light micrographs of structurally colored, white and pigmented bird skin showing differences between structurally colored and non-structurally colored skin in the thickness of collagen layers : (A) Chaemapetes unicolor, dark blue; (B) Numida meleagris, dark blue; (C) Tragopan temminckii, light blue; (D) Opisthocomus hoazin, dark. All specimens stained with Masson's trichrome, which stains collagen blue and cells red. All scale bars represent 100 µm, except in c, which represents. Abbreviations: c, collagen macrofibrils; cc, the collagenocytes; cp, capillaries; e, epidermis; m, melanosomes (From: Prum and Torres 2003). Transmission electron micrographs showing the very regular nanostructured arrays of dermal collagen fibers from: (A) Oxyura jamaicensis, light blue; (B) Numida meleagris, dark blue; (C) Tragopan satyra, dark blue; (D) Tragopan caboti, dark blue; (E) Tragopan caboti, light blue; (F) Tragopan caboti, orange; (G) Syrigma. All images were taken at 30000. All scale bars represent 200 nm (From: Prum and Torres 2003). Coherent scattering is differential interference or reinforcement of wavelengths scattered by multiple light-scattering objects (x, y). Coherent scattering of specific wavelengths is determined by the phase relationships among the scattered waves. Scattered wavelengths that are out of phase will cancel each other out, but scattered wavelengths that are in phase will be constructively reinforced and coherently scattered.

Scattering, in this case, simply means that light deviates from a straight path. Visible light is, of kites course, composed of many colors of light with distinct wavelengths. Red light has a long wavelength (700 nm whereas violet and blue light has a much shorter wavelength (400 nm). When visible light encounters particles with the same or larger diameter than its component wavelengths, those specific light photons are reflected. For example, particles that are 400 nm or slightly larger will selectively reflect blue light photons while allowing other light photons to pass. In the skin of birds light is reflected by collagen fibers (long, string-like protein molecules) that are arranged in a much more highly organized manner than in normal skin. For patches of skin that are a particular color (e.g., blue or green) all collagen fibers are the same thickness (Figure 8). As a result, each fiber scatters wavelengths of light that are in phase (Figure 10) and, therefore, are reinforced, producing very bright colors even more saturated than typical pigment-based colors. In addition to the reflection of light of certain wavelengths, skin structural coloration also requires a means to prevent the reflection or scattering of white light by deeper tissues below the color-producing nanostructures.

a worn path summary and analysis

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Birds cannot synthesize carotenoids so must acquire them in resume their diet. As a result, variation in carotenoid-based skin (or feather) coloration can provide conspecifics with information about individual quality and, specifically, the ability of different individuals to acquire a limited resource (Negro. For example, red-legged Partridges ( Alectoris rufa ) have bills and eye rings (bare skin not feathers) that are reddish due to the presence of carotenoids and individuals with redder bills and eye rings are in better physical condition (Pérez-rodríguez and viñuela 2008). Similarly, the yellow-orange skin on the legs, feet, and ceres all (skin at the base of the upper bill) of European Kestrels ( Falco tinnunculus ) is due to carotenoids and studies have revealed that male kestrels with more brightly colored skin are better hunters and. Red-legged Partridge for many birds, skin coloration is the result of optical interactions with biological nanostructures or, in other words, the microscopic structure of skin (Figure 7). Such structural colors occur in the skin, bill (ramphotheca legs and feet (podotheca) in about 129 avian genera in 50 families from 16 avian orders. Structurally colored skin is present in more than 250 bird species, or about.5 of all bird species (Prum and Torres 2003). Examination of the color, anatomy, and nanostructure of structurally colored skin, ramphotheca, and podotheca from several different species of birds indicates that color, including ultraviolet, dark blue, light blue, green and yellow hues, is produced by coherent scattering (i.e., constructive interference) of light from arrays.

(From: Negro. For those species of birds with bare skin on the head and neck and where skin coloration is altered by changes in blood flow (flushing thermoregulation was almost certainly the primary selective factor. However, in some species, flushing occurs in contexts unrelated to thermoregulation, such as during courtship or agonistic encounters. For example, the skin of turkeys becomes redder when courting females and when engaged in agonistic encounters with other males. This suggests that flushing can, for some species and in some contexts, also serve a signaling function. The ability to generate a deeper red coloration or maintain redder coloration for longer periods may be correlated with individual quality if doing so is energetically costly or potentially damaging to the body (Negro. The colored skin of many birds is due to pigments, molecules that differentially absorb and emit wavelengths of visible light. Carotenoids are the pigments responsible for colorful skin (as well as feathers) in many birds, and typically generate a red, orange, or yellow hue.

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a worn path summary and analysis

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Caracaras are relatively large birds with generally dark plumage that are typically found in relatively hot areas. When their body temperature increases, blood flow to the areas of bare skin myself increases as vessels dilate. This increased blood flow causes the skin to become deeper red in color, but, most importantly, enhances the loss of heat across the bare skin. Bare skin on the head and neck likely serves a similar function for many species of birds because many such birds are relatively large, dark-plumaged birds that occur at low latitudes where heat dissipation may be of great importance (Negro. A crested Caracara showing unfeathered (a) and feathered (b) areas of the head (From: Negro.

Micrographs of cross-sections of skin of a crested Caracara, a species with unfeathered areas on the head. (A) Unfeathered area (bare skin) on the face, and (B) feather-covered area on the head. Note the greater number of blood vessels in the unfeathered skin. Scale bars:. E, epidermis; c, collagen; er, erythrocytes; bv, blood vessels.

Chionis parrots, cuckoos, broadbills, bare-eyes (. Phlegopsis lyrebirds menura and helmet-shrikes prionops ) (Stettenheim 2000). More generally, patches of bare skin, other than the bill and legs, can be found in birds belonging to at least 19 different orders and 62 families (Negro. Colored unfeathered areas on the head and necks of birds may be important in (1) intra- and intersexual communication,. G., advertising status or quality, (2) thermoregulation, and (3) preventing the soiling of feathers for species that sometimes extend their heads into carcasses when feeding (e.g., vultures and condors).


Among birds with colorful skin (Figure 4 the coloration is due either to pigments, structural mechanisms in the epidermis, or to blood (and, specifically, hemoglogin in the red blood cells) in the superficial capillary network (Lucas 1970, Prum and Torres 2003). Structurally colored ornaments of a sample of the piciform and passeriform birds examined: (A). Selenidera reinwardtii, (B ramphastos vitellinus, (C ramphastos toco, (D neodrepanis coruscans, (E) Philepitta castanea, (F) Myrmeciza ferruginea, (G) Gymnopithys leucapsis, (H) Procnias alba, (I) Perissocephalus tricolor, (J) dyaphorophyia concreta, (K) Terpsiphone mutata and (L) leucopsar rothschildi. A, fj, reproduced with permission from vireo; b,c, l, reproduced with permission from Kenneth Fink; h, reproduced with permission from Nate rice; d, reproduced with permission from Steve zack; k, reproduced with permission from Tom Schulenberg (From: Prum and Torres 2003). Channel-billed toucan ( Ramphastos vitellinus ) Some species with bare skin on the head and neck alter skin color by changing blood flow to the area. For example, skin in the unfeathered areas of a crested Caracaras ( Polyborus plancus ) head has a much denser supply of blood vessels than skin in feathered areas (Figures 5 and 6). Although they sometimes feed on carrion, the bare skin of caracaras is most important for thermoregulation.

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(a) Typical non-breeding plumage. (b) daubing behavior; applying the pigment to plumage on the head, neck, and back. (c) Cosmetically colored ibis. (d) After post-breeding universities molt (From: Wingfield. Japanese Crested Ibis, among many species of birds, student the integument exhibits specialized modifications. For example, the skin on the head is unfeathered to varying degrees and distinctively colored in guineafowl, vultures, colies (. Colius and many storks, ibises, spoonbills, and cranes. The skin around the eyes is unfeathered and distinctively colored in other birds, such as cariamas, falcons, sheathbills (.

a worn path summary and analysis

Cross-section through the skin and of a bird or mammal (From: Lillywhite 2006). Besides forming a dynamic barrier that regulates water loss through the skin, epidermal lipids may also have antimicrobial properties and offer protection against ultraviolet light (Menon 1984). In addition, epidermal lipids are used for cosmetic coloration in the japanese Crested Ibis (. Nipponia nippon ; Wingfield. Before breeding, the skin of the neck and head starts secreting a black substance that the ibises apply to their white plumage (Figure 3). The extent of the secretory skin area and how much of the plumage is covered by the cosmetic varies among individuals and this variation plays a role in mate choice. Young birds do not produce the black secretion at all. Plumages of the japanese Crested Ibis.

temperatures of birds, increased heat production during flight, insulation by plumage and the lack of sweat glands, require a higher rate of evaporative cooling through a relatively "leaky" epidermal permeability barrier. Importantly, however, the relatively permeability of the avian epidermis can be modified. For example, menon. (1996) found that, within 16 hours of water deprivation, adult Zebra finches can reduce water loss via the epidermis by 50 by the rapid secretion of epidermal lipids. A similar ability to influence water loss by regulating secretion of epidermal lipids has been reported in larks (Haugen. 2003 house Sparrows (. Passer domesticus ; muñoz-garcia and Williams 2008 and the tropical Dusky antbird (. Cercomacra tyrannina ; muñoz-garcia and Williams 2007). Feathered (feather tracts) and unfeathered (apteria) areas of the avian integument (From: Chuong.

The outer layer, the epidermis, is generally very thin and pliable. The dermis is thicker than the epidermis and contains blood vessels, fat deposits, nerves and free nerve endings, several types of neuroreceptors, and smooth muscles that move the feathers (Lucas and Stettenheim1972). The epidermis, the most superficial layer of the skin, is thinner in birds than in mammals of comparable size, flexible, and smooth, and this is due, at least part, to selective pressures to minimize body weight for more efficient flight (Spearman 1966). The epidermis is thinnest in areas covered by feathers (both feather tracts and apteria; Figure 1) and thickest in exposed, featherless areas, including metamorphosis the covering of the beak (rhamphotheca) and feet (podotheca). The epidermis has two main layers a superficial stratum corneum and a deeper strateus germinativium (Figure 2). The stratum corneum consists of flattened, keratinized cells. These cells are called keratinized because they contain a protein called keratin (and, specifically, beta keratin) that, along with extracellular lipids (fats) produced by epidermal cells, provide a tough, permeability barrier that prevents excessive evaporative water loss. The stratum corneum can be viewed as having a brick-and-mortar organization, with the keratin-enriched cells forming the bricks and the extracellular lipids the mortar (Elias and Menon 1991).

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Avian integument, bIO 554/754, ornithology, avian Integument, epidermis. Integement modifications, skin color, skin color - structural, claws. Rhamphotheca, literature cited, the functions of bird skin are the same as for other vertebrates to keep out pathogens and other potentially harmful substances, retain vital fluids and gases, and serve as a sensory organ. The continual vegetarianism renewal of the skin acts to repel parasitic microorganisms. The skin of birds also produces and supports feathers. With feathers, the skin also plays an important role in thermoregulation. Although largely covered by feathers, the integument is unfeathered on the beak, feet, and, in some species, other areas. In contrast to mammals, avian skin does not have sweat glands and sebaceous glands. Avian skin consists of two layers, the epidermis and dermis.


A worn path summary and analysis
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