title: Fluid dynamic model of invertebrate sperm chemotactic motility with varying calcium inputs.
abstract: In a marine environment, invertebrate sperm are able to adjust their trajectory in response to a gradient of chemical factors released by the egg in a process called chemotaxis. In response to this chemical factor, a signaling cascade is initiated that causes an increase in intracellular calcium (Ca(2+)). This increase in Ca(2+) causes the sperm flagellar curvature to change, and a change in swimming direction ensues. In previous experiments, sperm swimming in a gradient of chemoattractant have exhibited Ca(2+) oscillations of varying peaks and frequency. Here, we model a simplified sperm flagellum with mechanical forces, including a passive stiffness component and an active bending component that is coupled to the time varying Ca(2+) input. The flagellum is immersed in a viscous, incompressible fluid and we use a fluid dynamic model to investigate emergent trajectories. We investigate the sensitivity of the model to the frequency of Ca(2+) oscillations. In this coupled model, we observe that longer periods of Ca(2+) oscillation corresponds to circular paths with greater drift. In contrast, shorter periods of Ca(2+) oscillations corresponded to tighter search patterns. These outcomes shed light on the relation between Ca(2+) oscillations and different searching trajectories and strategies that invertebrate sperm may utilize to reach and fertilize the egg in a marine environment.
authors.affiliation: Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA 01609, USA. sdolson@wpi.edu
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Olson
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002633:Chemotaxis / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D012617:Sea Urchins / Q000502:physiology*; D013081:Sperm Motility / Q000502:physiology*; D013082:Sperm Tail / Q000502:physiology*
chemical_list: D002118:Calcium