Effects of Small Colony Formation on the Swimming and Feeding of Choanoflagellates

Choanoflagellates, the closest living relative to animals, are unicellular eukaryotes that can form colonies. Each cell has an ovoid body and a single flagellum surrounded by a collar of microvilli. A single cell swims by waving its flagellum, which also creates a water current that brings bacteria to the collar of prey-capturing microvilli. In this project, we use a modified regularized Stokeslet method to examine the effects of small colony formation on the swimming and feeding performance of choanoflagellates .

To study their feeding and swimming behaviors, we calculate the inward flux of fluid into the collar of each cell and the translational and rotational velocities of the colony due to the prescribed flagellar motions. We find that reducing the angle between cells in a small colony increases the average speed of the colony and the inward flux of each cell. For a two-cell colony, an increasing difference in their initial flagellar phases causes a linear increase in velocity and a difference in inward fluxes due to asymmetrical flow patterns. In general, the effect of the initial flagellar phase is only significant when all of the flagella beat on the same plane. Colonies are slower on average and have a smaller total flux per cell compared to a free-swimming cell. Since small colonies have similar work performance, they become less efficient as the number of cells increases.