Meeting Abstract
When organisms locomote in nature, they must navigate through complex habitats that vary on many spatial scales, and they are buffeted by turbulent wind or water currents and waves that also vary on a range of spatial and temporal scales. We have been studying the effects of body shape and of swimming or crawling behavior by microscopic organisms on their motion through the environment as they are carried by turbulent ambient flow. Using both mathematical models and experiments with the microscopic larvae of bottom-dwelling marine animals, we found that local shear rotates small organisms, thereby changing their swimming direction. While spherical bodies keep spinning in shear, elongate bodies rotate until they line up with the shear. Swimmers travel differently in turbulent flow than do non-swimmers, and are more likely to encounter nearby surfaces but less likely to remain there than non-swimmers. Thus, microscopic organisms can bias the way that they are transported by ambient flow. Body shape and orientation also affect the drag on small organisms crawling on surfaces, so shape coupled with the adhesive strength of crawlers constrains the flow microhabitats in which they can operate.
