Effects of prey capture on the swimming and feeding performance of choanoflagellates.

Choanoflagellates, eukaryotes that are important predators on bacteria in aquatic ecosystems, are used as a model system to study the evolution of animals from protozoan ancestors. The choanoflagellate, Salpingoeca rosetta, has a complex life cycle that includes unicellular and multicellular stages, provides a model system to study the consequences of different cell morphologies. A unicellular S. rosetta has an ovoid cell body and a single flagellum surrounded by a collar of microvilli. The cell swims by waving its flagellum, creating a water current that brings bacteria to the collar of prey-capturing microvilli. One measure of the performance of a suspension-feeding organism is the volume of fluid that it can move into its collar during a beat cycle. The inward flux of fluid acts as a proxy for the rate of bacterial capture. Here we use a regularized Stokeslet framework to model the hydrodynamics of a unicellular choanoflagellate, the captured bacterial prey, and their effect on swimming performance and clearance rate. We compare model predictions with high-speed microvideography. Moreover, we will discuss current assumptions, and future model improvements that, with coordinated lab experiments, will help us probe this intriguing biophysical system.