NSF Postdoctoral Fellowship in Biology: From helical fibers to vortical flow: unravelling the contributions of muscle geometry and physiology to swimming performance

Jimenez, Yordano Eleazar, Medford MA

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2022, Broadening Participation of Groups Underrepresented in Biology. The Fellowship supports a research and training plan for the Fellow that will increase the participation of groups underrepresented in biology. The goal of the Fellow’s research is to understand how animal movement is affected by small differences in muscle anatomy. This research project begins with a simple observation: bending from side to side is the oldest and most common form of vertebrate locomotion. Nearly all fishes swim by bending their bodies back and forth. For most vertebrates, in fact, to move is to bend. However, animals that use body bending are subject to a biomechanical constraint: as muscles flex the spine, muscle tissue deforms unevenly. Muscle close to the spine only shortens a little, and muscle far from the spine shortens a lot, and neither of these are optimal. This uneven muscle deformation risks sabotaging locomotor performance. This research seeks to determine whether body-bending vertebrates may have evolved specialized muscle fiber geometries to solve this biomechanical problem. To answer these questions, the Fellow will use multiple cutting-edge approaches to analyze and model fish motion in water. To increase participation in STEM, the Fellow will serve in leadership roles in the Society for the Advancement of Chicanos and Native Americans (SACNAS). To determine how vertebrates have solved the biomechanical problem of bending, the Fellow is conducting two studies examining fish and their geometrically complex axial musculature. The work will involve multiple approaches including 3D modelling, in vitro muscle physiology, and particle imaging velocimetry (PIV) to measure patterns of water flow. The first study measures body curvature, muscle activity, and fluid flow in largemouth bass swimming at different speeds. The second study uses a classic technique called a “work loop” to measure contractile performance for muscle fiber bundles with different fiber geometries, as calculated using a 3D mathematical model and 3D measurements of muscle fiber angle. The data from these experiments will be combined to generate a spatial quantitative map of internal muscular forces and external hydrodynamic forces. These results will determine if the complex helical fiber geometry of fish muscles solves the bending problem. This research will also expand the understanding of how force generated within muscles is transmitted into the water, and whether fish shift strategies at different swimming speeds. For long-term career development, the Fellow is being trained in student mentorship and lab management. To broaden participation of underrepresented minorities, the Fellow will participate in leadership programs offered by SACNAS and will also participate in outreach at the Museum of Science in Boston. 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.