Sperm Pairing and Measures of Efficiency in Planar Swimming Models

Sperm of certain species engage in cooperative swimming behaviors which result in differences in velocity and efficiency of swimming, as well as ability to effectively fertilize the egg. In particular, Monodelphis domestica is a species of opossum whose sperm often swim cooperatively as a pair, with heads fused together. In order to understand the empirical effects of cooperative swimming behaviors, we propose a simple preferred-curvature-based model to model individual and paired sperm using the method of regularized Stokeslets to model the viscous fluid environment. The effects of swimming freely versus paired swimming, phase relationship, and the angle at which sperm heads are fused are investigated. Results are consistent with previous modeling work for free swimmers. Paired (fused) swimming results also compare well with experimental work, and provide evidence for optimal geometrical configurations. This indicates that there may be a fluid mechanical advantage to such cooperative motility behaviors in sperm swimming