Biology Letters
Restricted accessBiomechanics

Iridescent colour production in hairs of blind golden moles (Chrysochloridae)

Holly K. Snyder

Holly K. Snyder

Department of Biology and Integrated Bioscience Program, University of Akron, Akron, OH 44325-3908, USA

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Rafael Maia

Rafael Maia

Department of Biology and Integrated Bioscience Program, University of Akron, Akron, OH 44325-3908, USA

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Liliana D'Alba

Liliana D'Alba

Department of Biology and Integrated Bioscience Program, University of Akron, Akron, OH 44325-3908, USA

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Allison J. Shultz

Allison J. Shultz

Department of Biology, San Diego State University, San Diego, CA 92182, USA

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Karen M. C. Rowe

Karen M. C. Rowe

Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA

Sciences Department, Museum Victoria, Melbourne, Victoria 3001, Australia

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Kevin C. Rowe

Kevin C. Rowe

Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA

Sciences Department, Museum Victoria, Melbourne, Victoria 3001, Australia

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and
Matthew D. Shawkey

Matthew D. Shawkey

Department of Biology and Integrated Bioscience Program, University of Akron, Akron, OH 44325-3908, USA

[email protected]

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    Relative to other metazoans, the mammalian integument is thought to be limited in colour. In particular, while iridescence is widespread among birds and arthropods, it has only rarely been reported in mammals. Here, we examine the colour, morphology and optical mechanisms in hairs from four species of golden mole (Mammalia: Chrysochloridae) that are characterized by sheens ranging from purple to green. Microspectrophotometry reveals that this colour is weak and variable. Iridescent hairs are flattened and have highly reduced cuticular scales, providing a broad and smooth surface for light reflection. These scales form multiple layers of light and dark materials of consistent thickness, strikingly similar to those in the elytra of iridescent beetles. Optical modelling suggests that the multi-layers produce colour through thin-film interference, and that the sensitivity of this mechanism to slight changes in layer thickness and number explains colour variability. While coloured integumentary structures are typically thought to evolve as sexual ornaments, the blindness of golden moles suggests that the colour may be an epiphenomenon resulting from evolution via other selective factors, including the ability to move and keep clean in dirt and sand.

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