Hoa Nguyen, Trinity University
Authors: Emma Ross (Trinity University), M.A.R. Koehl (University of California, Berkeley, Integrative Biology), Lisa Fauci (Tulane University, Mathematics), Ricardo Cortez (Tulane University, Mathematics)
2022 AWM Research Symposium
Recent Advances in Mathematical Biology

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, being free-swimming vs. sessile, or being a single cell vs. a multicellular colony. 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, which also creates 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. While this is a good measure of uptake of dissolved nutrients, it is only an approximate measure of prey capture. Here we use a regularized Stokeslet framework to model the hydrodynamics of a unicellular choanoflagellate, the captured bacterial prey of non-zero volume, and their effect on swimming performance and clearance rate. We compare the model predictions with high-speed microvideography. Moreover, we will discuss current model assumptions, and future model improvements that, together with coordinated lab experiments, will help us probe this intriguing biophysical system.

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