The effect of ambient flow on Vorticella convallaria 3D orientation and feeding behavior

Vorticella convallaria are microscopic sessile suspension feeders which live attached to substrates and are ubiquitous in aquatic environments. They depend on a self-generated current to feed and help maintain the health of aquatic ecosystems by consuming bacteria and detritus. They can also improve efficiency of wastewater treatment and bioremediation. Their environmental impact is mediated by their feeding rate, which is reduced when recirculating eddies deplete the supply of food particles in their feeding current. Previous work found that when organism feeding currents interact with ambient flow, feeding rates are highly dependent on organism orientation relative to the surface and the flow, with some orientations leading to recirculation. We thus hypothesized that individuals actively orient themselves with positions most favorable for feeding. We cultured organisms attached to the bottom surface of a flow chamber and exposed them to unidirectional laminar flow at four speeds. We recorded the 3D orientation of individuals over a span of 20 minutes using a simultaneous top and side view microscope. We determined that the orientation of the cell body and stalk are impacted by flow and observed changes to their feeding patterns and feeding rate as flow speed increased.