Playing with Light: Diving into the Material Tricks Sharks and Rays Use to Make Color

Description

Although many natural colors, like many man-made ones, are pigment-based, Nature has an arguably more ingenious solution: these so-called structural colors are caused not by absorbing particular light wavelengths, but by reflecting them using nanoscale structures, often arranged in exquisite microscopic patterns. The mechanisms, materials and forms that generate structural colors are enticing for biologists, material scientists and designers alike, since these colors are often brilliant (for attracting mates or scaring predators), have interesting qualities depending on how they’re viewed (e.g. many structural colors are iridescent), and typically don’t fade as pigmented colors do. Structural color has evolved multiple times and in a massive range of organisms, from bacteria to mammals, and yet has never been seen in sharks/rays (elasmobranch fishes), despite the huge public interest in this group and many of the species having complex or even vivid color patterns. My preliminary investigations suggest these animals do indeed have structural color: here, I explore this in a project incorporating reciprocal anatomical, materials and photonics approaches. To put my finescale tissue investigations in context, I will establish a baseline by generating the first histological key for skin anatomy across species, also compiling records of the diverse colorings in sharks/rays and their links to behavior and habitat. I will then use high-resolution materials science tools to determine what makes colored skin distinct, characterizing mechanical and material properties of skin tissues in two model species exhibiting different blues (nature’s rarest color), focusing on ultrastructural features that are likely culprits for color generation, while also measuring the precise color fingerprints these tissues reflect in natural light. These data on form (ultrastructure) and function (color) will provide clues to the structural roots of color generation, their relevance to animal ecology, and the first view into how evolution shaped tissue architectures for optical behavior in sharks/rays, but also, since this lineage is old and exhibits a variety of unique anatomical aspects, perhaps novel material solutions for color and light management. Results will also offer vital inputs for downstream manufacturing of multifunctional materials: flexible materials with durable, radiant color have vast technological potential to resolving critical challenges in wearable biomedical devices, biosensors, and polarisation-controlling optics, and or soft materials that are flexible and hydrodynamic, but also invisible under water. In these ways, the project will inform fields from evolutionary biology to nanophotonics, while providing unique multidisciplinary training and a forward-thinking, collaborative research space.