Title: Fish Scales: Morphology, Evolution, and Function
Abstract: Fish scales are plates of dermal bone that are embedded in the dermis and epidermis of most fish species. Scales occur in many forms and past research has provided a framework to categorize scale types and a foundation for describing scale morphology. This thesis seeks to further our knowledge of scale morphology, evolution, and function using a combination of established, modern, and novel methods to quantify scale morphology in both intra- and inter-species contexts. In my first chapter, I describe how a method called gel-based stereo-profilometry can be used to image and quantify the three-dimensional topography of biological surfaces of interest, especially scales. In my second chapter, I use both gel-based profilometry and micro-computed tomography (µCT) to show that scale morphology of the bluegill (Lepomis macrochirus) is different qualitatively and quantitatively among regions of its body. In my third chapter, I use µCT and histology to study scale morphology in bigeye tuna (Thunnus obesus) and I show that regions on the anterior body of bigeye tuna have large scales made of cellular bone that are filled with adipocytes. In my fourth chapter, I quantify scale morphology across 59 damselfish (Pomacentridae) species that exhibit multiple transitions between pelagic and benthic feeding ecologies. With this comparative approach, I ask if scale morphology fits models of ecologically-driven evolution, thus seeking to link scale morphology to function. Finally, in my fifth chapter I briefly review our knowledge of elasmoid scale morphology and function, and I also demonstrate the quantitative effect mucus and epidermis have on scale morphology by in vivo imaging of the surface topography of seven fish species.
Committee: George Lauder, Diego Bernal (University of Massachusetts, Dartmouth), Andrew Biewener, Stephanie Pierce