Pteridines as Reflecting Pigments and Components of Reflecting Organelles in Vertebrates

Abstract

This paper reviews evidence for the presence of pteridines in iridophores, leucophores, and xanthophores in a wide variety of vertebrate chromatophores, and argues that the chemical and functional distinction between pterinosomes and reflecting platelets is not as clear-cut as previously believed. Observations indicate that: (1) Pteridines may, either alone or in conjunction with purines, form pigment granules that reflect light, (2) these pigment granules are highly variable ranging from fibrous pterinosomes to typical reflecting platelets and may be colored, reflect white light, or be iridescent, and (3) many "leucophores" probably contain typical pterinosomes and presumed associated colorless pteridines and are therefore more closely related to erythrophores and xanthophores than to iridophores with which they are usually classified. We propose that the classification of pigment cells should be modified to reflect these facts.

Structural colouration of avian skin: convergent evolution of coherently scattering dermal collagen arrays

“…These results confirm the conclusion that birds, like mammals, have evolutionarily lost integumentary iridophores (Oliphant et al, 1992;Bagnara, 1998), although birds retain iridophores as an important mechanism of structural colour production in the iris (Oehme, 1969;Ferris and Bagnara, 1972;Oliphant, 1981Oliphant, , 1987aOliphant et al, 1992;Oliphant and Hudon, 1993).…”

Multiple Pigment Cell Types Contribute to the Black, Blue, and Orange Ornaments of Male Guppies (Poecilia reticulata)

“…Interestingly, some larval chromatophores of medaka contain reddish pigment that they lose during further development, thereby becoming whitish leucophores [32], [56]. This raises the possibility that some organelles can contain several pigment types and might change in the course of development [56], [57]. Moreover, pigment cells containing two types of pigment organelles, so-called ‘dichromatic chromatophores’, have been described in some vertebrates.…”

New perspectives in gaze sensitivity research

“…Several hypotheses have suggested that eye coloration may be related to ecology (Craig & Hulley, 2004;Amat, 2013), aggression and dominance (e.g., Martin & Hengstebeck, 1981;Craig, 1988;Volpato et al, 2003), mate recognition and/or sexual selection (e.g., Smith, 1967;Amat, 2013). In support of the sexual selection hypothesis, it has been proposed that the intensity of iris color in birds may be an honest indicator of metabolic efficiency through the anti-oxidant activities of hemoglobin or pterins present in red-colored irides (McGraw, 2006;Oliphant & Hudon, 1993). To date, the most convincing evidence for a potential function of iris color in non-primates is that conspicuous eyes may be linked to nest guarding in jackdaws, to signal to competitors to keep away from occupied cavities (Davidson, Clayton, & Thornton, 2014).…”