Fish skin is a complex structure characterized by long collagen fiber which wrap in a helical pattern around the body. Though all fish have this basic structure, details such as fiber arrangement and scale density varies extensively across species. For decades, scientists have been intrigued by these cross-helically arranged fibers.
Several studies have looked at their structure both at a macro and microscopic level and some have even examined the material properties of the skin on a few specific fish (Danos et al., 2008; Lauder, 2015; Long et al., 2002). Other studies have revealed the importance of skin stiffness in the swimming behavior of certain fish, such as the Longnose Gar (Long et al., 1996). Despite this handful of studies, no one has extensively explored the role played by the skin in determining functional capabilities of important behaviors like swimming. In addition, no study has yet characterized the diversity of skin properties across an entire clade of fishes to answer question about how the diverse morphology may evolve.
The goal of this project is to characterize the stiffness and fiber angle of skin across a group of fishes that demonstrate a diverse morphology and ecology: Cottoidei (sculpins). To execute this study, the investigator will use techniques from both engineering and ecology. We will construct a bi-axial material testing system, and use an Arduino program to control it and collect stiffness data on skin from several species of sculpin. Next, we will use a dissection scope and camera to measure the fiber angle of the skin. Finally, we will integrate the results of hundreds of our material testing experiments with a database morphological and ecological data and the most current phylogenetic hypothesis for cottoids to identify the major covariates of skin stiffness and structural properties.