NSF Award
2114561
Spiders are important predators of insects and other small animals, and the group has nearly 50,000 described species. They are one of the most diverse and numerous groups of animals and occupy a wide variety of habitats; spiders also play an essential role in controlling pest populations. While great advances have been made in understanding how spiders use silk and venom to capture prey, very little is known about the main feeding structures of spiders, the chelicerae. These in some respects function like jaws of vertebrates since they are used to grasp and process prey. This research focuses on how the chelicerae are used during the predatory strike, when the spider grasps the prey and injects it with venom, and how the shape, speed and strength of chelicerae vary in different groups of spiders. The researchers will compare the anatomy and movements of chelicerae in a wide variety of spiders to better understand the evolution of feeding in the group. This work will also examine details of the super-fast predatory strike, found in certain types of spiders, and determine how it evolved. In addition to revealing the function and evolution of spider chelicerae, the project introduces spider biology to the next generation of scientists, with outreach to several groups ranging from high-school students to postdoctoral scholars. Results from this research will also be used to engage and educate the public, including school-aged children, through hands-on lessons that will be displayed at the National Museum of Natural History and used in a summer day camp at the University of Maryland.<br/><br/>This research focuses on the comparative functional morphology of spider chelicerae, and tests the hypothesis that a fundamental biomechanical principle, the force-velocity trade-off, explains the diversification of their morphology and predatory strike dynamics. It is widely assumed that lever-based skeletomuscular systems are optimized to produce either high forces or high velocities, but not both simultaneously. Predictions of the force-velocity hypothesis will be tested using a broad sample of species from across the spider tree of life, including the “trap-jaw” spiders, some of which have predatory strikes that are the fastest movements known among arachnids. Structural details of the exoskeleton and musculature will be quantified through analysis of Computed Tomography scans and histological sections, and functional performance variables such as strike velocity will be measured through analysis of high-speed videos. A molecular phylogeny will be generated and used to provide the historical framework for examining the evolution of morphology and strike performance. Phylogenetically-informed statistical analyses will be used to determine whether the correlations between form and function anticipated by the force-velocity trade-off are consistent with the biomechanical diversity observed in spiders. The results will offer insights into the evolution of form and function in skeletomuscular systems and provide a rich source of new information on spider biology. This award is co-funded by two programs in the Directorate for Biological Sciences, the Systematics and Biodiversity Science Program in the Division of Environmental Biology, and the Physiological Mechanisms and Biomechanics Program in the Division of Integrative Organismal Systems.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
