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Numerous animals exhibit remarkable adaptations for dynamically altering skin coloration. For instance, chameleons modify guanine crystal spacing in their cells, flounders regulate skin pigment visibility, and cephalopods utilize complex light-diffusing structures to achieve effective camouflage. While shark skin is often perceived as grey, some species demonstrate diverse coloration and camouflage strategies, including countershading and bioluminescence. Recent reports suggest that great white sharks possess dynamic camouflage, as evidenced by the great white shark's skin color changes to a lighter hue when exposed to adrenaline, while melanocyte-stimulating hormone (MSH) causes a darker hue. Our study on blue sharks (Prionace glauca) reveals a potential nanostructural mechanism for this via a direct association between shark coloration and their skin's tooth-like dermal denticles, which are well known for their hydrodynamic properties. We show that each denticle produces highly saturated, non-iridescent color through nanoscale structural interactions within its pulp cavity. Inside denticles, varying spatial interactions between pigment cells and cells packed with complex crystal stacks (likely guanine) mediate the perceived color in different body regions. These cellular associations, however, also offer a palette whereby small changes in tissue architecture can manifest as local color changes. Our optical observations of excised blue shark skin reveal it can transition from blue to green, gold to slate gray in response to external stimuli, such as changes in humidity. This suggests that our identified structural color mechanisms provide a pathway for dynamic camouflage, opening an unexplored window into shark ecological adaptations and novel structural mechanisms for producing mutable colors.
Viktoriia Kamska (City University of Hong Kong )
Postdoctoral Researcher
Dr. Viktoriia Kamska is a multidisciplinary researcher and wildlife science artist specializing in the intersection of biological coloration, structural mechanics, and environmental interaction. Her current postdoctoral work at the City University of Hong Kong focuses on the coloration mechanisms in blue sharks, exploring how the architectural arrangement of nanoscale structural components—considering their optical properties—produces vivid camouflages, including a vibrant blue. Her research enhances her understanding of shark biology and offers insights into bio-inspired materials. Dr. Kamska's academic journey began in her native city, Odesa, Ukraine, where she earned her first Master's in genetics and molecular biology. She further developed her expertise through the MEME Erasmus Mundus double-degree Master's program in Evolutionary Biology. She earned her second Master's at Uppsala University for her work on the evolutionary aquatic to terrestrial locomotion transition of the Devonian fish Hyneria. Her third Master's from Ludwig-Maximilians University of Munich explored the 3D anatomy of the world's smallest known frogs. At the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, Dr. Kamska pursued her doctoral research, delving into the neuroethology and biomechanics of birds. Her project uncovered potential additional mechanosensory functions of the lumbosacral organ (LSO) in birds, contributing to their agility and locomotion. Throughout her career, Dr. Kamska has embraced the synergy of art and science, viewing them as complementary tools that enrich her research and public engagement. Her innovative, cross-disciplinary approach helps her uncover non-trivial solutions to complex challenges, using her artistic vision combined with rigorous scientific methods to explore enigmatic structures in nature.
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