Mentor: Dr. Mark Galatowitsch
Presenter: Will Baughman
Title: Ant Foraging: Collective Decision-Making
Abstract: Foraging is a vital activity for ants so they can provide the food resources necessary to sustain the colony “superorganism.” Because it is readily observed, ant foraging activity has been an area of great scientific interest. I investigated the rate at which Lasius ant colonies discover food sources and exploit them. Colonies were excavated on the Centre Campus to establish artificial nests. In the lab these nests were connected to bifurcated tubing leading to two smaller foraging arenas. At three-day intervals workers from each colony were given a choice between two arenas containing food and water, respectively. The number of ants accessing each arena over a 30 minute period following food discovery was recorded. The majority of colonies favored arenas containing food, but no statistically significant preference was observed. These results suggest significant limitations on resource identification exist, complicating efforts to utilize food sources. Future research will consider the influence of threat stimuli on foraging behavior.
________________________________________________________________________________________________
Mentor: Dr. Mark Galatowitsch
Presenter: Xavier Ovalle
Title: Between a Rock and a Hard Place | Drying Effects on Psephenus herricki
Abstract: Climate change is altering temperature and precipitation regimes which causes water availability in aquatic habitats like streams to become increasingly irregular, with frequent strong floods and prolonged dry periods. These changes could be a serious threat to aquatic invertebrates if they are not adapted to these stresses. Waterpennies are beetle larvae are common in Kentucky streams with evidence of resistance to stream drying. This research explores the strategies waterpennies employ to endure drying stress. Laboratory experiments tested whether waterpennies diapause and/or seek moist substrate environments to resist desiccation. We observed that they do not go into diapause, but remain active and likely seek moist microhabitat refuges. Although survivorship and moisture level are unrelated, there was evidence that rocks promote their ability to resist drying. Our research provides insight for how invertebrates may handle irregular drying conditions. It may be more beneficial to search for moist microhabitats than to enter diapause so they can more quickly exploit their environment when the water returns.
________________________________________________________________________________________________
Mentor: Dr. Daniel Scott
Presenters:
Title:
Abstract:
________________________________________________________________________________________________
Mentor: Dr. Bruce Rodenborn
Presenter:
Title: Tracking energy sinks when internal waves reflect from boundaries
Abstract: Many geophysical fluid systems have a density that varies as a function of height. For example, both the Earth’s ocean and atmosphere are such stratified fluids. The density variation allows for a special type of wave, called internal waves, to propagate within the fluid. In the ocean, these waves are hidden, but in the atmosphere, we often see clouds that appear in bands, which is evidence of internal waves propagating in the atmosphere. The Rodenborn lab studies these systems using laboratory experiments where the density is varied using a salt solution and measure the motion of the fluid using cameras and laser illumination. We present interesting results that may help explain why continental slopes are eroded to a particular angle throughout the world. We recently discovered that there is a wave reflected back toward the source when internal waves reflect from a solid boundary in our numerical simulations, which has not been reported in the literature. We seek to reproduce this result in our laboratory experiments and report on our progress in characterizing this phenomenon.
________________________________________________________________________________________________
Mentor: Dr. Bruce Rodenborn
Presenters: Asha Ari and Alexandra Boardman
Title: Boundaries Affect Bacterial Swimming
Abstract: The world of microorganisms is dominated by viscous dissipation, which is known as a low Reynolds number environment. As a free swimming bacterium approaches a boundary, both the propulsive force and torque on its helical flagellum increase rapidly and bacteria spend the majority of their life cycle near boundaries. We use scaled macroscopic experiments to measure this functional dependence of the the force and torque as a constrained rotating helical flagellum approaches a boundary. We keep the Reynolds number in the experiments much less than unity to model bacterial fluid dynamics. These Reynolds-number-scaled experiments are compared with numerical simulations made by Hoa Nguyen and Nicholas Coltharp at Trinity University. The computations find a similar functional dependence of force and torque on boundary distance. We also compare the results to biological measurements conducted by Orrin Shindell at Trinity that use total internal reflection fluorescence microscopy to simultaneously measure the distance to the boundary and the dynamics of the bacteria in an effort to understand how bacterial morphology is affected by swimming near a boundary.
________________________________________________________________________________________________
Mentor: Dr. Bruce Rodenborn
Presenters: Zaid Ahmen and RJ Smith
Title: The Three-Link Swimmer at Low Reynolds number
Abstract: E.M. Purcell postulated in 1976 that simplest geometry that can result in locomotion in a low Reynolds number environment consists of three links connected by two joints. This simple conceptual model has led to a broad field of study in physics and mechanical engineering because it may provide insights into why microorganisms use particular gaits to move, where a gait is defined as a repeating sequence of motions. For the three-link swimmer, a gait consists of the motion of the two angles that join the three segments of its body. Hatton and Chosett (2013) developed an abstract theory to predict the motion of a three-link swimmer, which has only been tested using numerical simulations and using robots swimming in sand. We seek to test their theory using a macroscopic robot placed into highly viscous silicone oil so that the robot is swimming at low Reynolds number for the first time.
________________________________________________________________________________________________