NSF Postdoctoral Fellowship in Biology FY 2017: Evolutionary morphology and cranial constraints in piranhas, pacus, and their allies

Kolmann Matthew A, Louisville KY

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2017, Broadening Participation of Groups Under-represented in Biology. The fellowship supports research and training of the fellow utilizing biological collections in innovative ways. Piranhas and their allies number almost 100 species and despite deceptively simple jaws, these fishes consume prey ranging from whole fishes to plant matter like nuts, fruits, and leaves. Researchers can understand how and why biomaterials and structures have changed by studying the history of predators and their prey, and noting which behaviors, structures, and materials keep evolving in tandem (evolutionary convergence). The first step in understanding how anatomy has evolved is building an evolutionary genealogy (phylogeny) of living piranhas, pacu, and their relatives to use as a framework. This project will then examine how the feeding anatomy of piranhas and their allies is constructed, how these structures perform when feeding on different prey, and map these traits across the evolutionary history of these fishes. The fellow will construct a cutting-edge phylogenomic tree for serrasalmid fishes using targeted exon capture methods. These evolutionary relationships will be used as a framework for understanding feeding trait evolution, visualized through iodine-enhanced contrast staining coupled with micro-computed tomography (micro-CT). The fellow will use biomechanical modeling methods like FEA (finite-element analysis) to examine how different skull shapes resist stresses during feeding, and quantify feeding performance by analyzing muscle morphology and jaw lever dynamics measured from micro-CT imaging. This project proposes that the skulls of piranhas will show evolutionary trade-offs among cranial architectural strength, tooth shape, and feeding performance. Certain combinations of these traits will also be correlated with specific diets like scale-eating, fruit-eating, and piscivory, among others. This project utilizes molecular collections from museums to further our understanding of the evolutionary relationships of charismatic fishes like piranhas. Morphological imaging of museum specimens will generate a database of piranha CT models for teaching and outreach methods, free for anyone to download and 3D print. Training goals include the fellow gaining experience in some of the most advanced techniques for visualizing anatomy and modeling the material and architectural behavior of these structures. Broader impacts include educational outreach targeting university and pre-university students with speech disabilities, engaging these student's interests in science, and reinforcing their confidence and ability for entering academia and other research-based professions. Results from the studies will also be published in peer-reviewed journals and shared at scientific meetings.