ABSTRACT SUCTION FEEDING IN THE CARNIVOROUS BLADDERWORT UTRICULARIA Suction feeding is an important feeding mode in aquatic organisms and is used across a considerable size range, from tadpoles to whales. Our current understanding is based on how adult fish feed and suggests that suction feeding is not effective for organisms just a few millimeters in size. All suction feeders have to overcome the inertial and viscous forces exerted by the water when sucking in water plus prey, yet only the inertial forces contribute to prey capture, while viscous forces contribute just to the cost and reduce the effectiveness of prey capture. Large predators do not need to complete their suction strikes as quickly as small predators because the contribution of viscous forces is low. We therefore predicted that (1) small suction feeders complete feeding events more quickly than large suction feeders, and that (2) smaller suction feeders approach the lower size limit and hence cannot generate the same high flow speeds as larger suction feeders. We focused on two species of the aquatic carnivorous plant bladderwort, Utricularia gibba and U. vulgaris , that capture zooplankton in traps that are just 1-5 mm long. We quantified the movements of the bladders during feeding strikes and their peak flow speeds. We found that bladderwort feeding strikes are much briefer than those of adult fish, and that the smaller bladderwort species, U. gibba , generates slower flows than the larger U. vulgaris, suggesting that U. gibba feed near the lower size limit . Matthew David Brown May 2016 SUCTION FEEDING IN THE CARNIVOROUS BLADDERWORT UTRICULARIA by Matthew David Brown A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology in the College of Science and Mathematics California State University, Fresno May 2016 APPROVED For the Department of Biology: We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree. Matthew David Brown Thesis Author Ulrike K. Müller (Chair) Biology Otto Berg Chemistry John V. H. Constable Biology For the University Graduate Committee: Dean, Division of Graduate Studies AUTHORIZATION FOR REPRODUCTION OF MASTER’S THESIS X I grant permission for the reproduction of this thesis in part or in its entirety without further authorization from me, on the condition that the person or agency requesting reproduction absorbs the cost and provides proper acknowledgment of authorship. Permission to reproduce this thesis in part or in its entirety must be obtained from me. Signature of thesis author: ACKNOWLEDGMENTS I would like to recognize the Biology Department and congratulate all of their staff who make scientific research possible here at Fresno State. I am always taken aback by the amount of unbelievable talent and tireless effort that make the graduate program both exciting and enlightening. My research on Suction Feeding in the Carnivorous Plant Utricularia is the product of not only my hard work and determination but the unbelievable support available to me by the other professors and colleagues. First off I would like to acknowledge my graduate adviser Dr. Ulrike Muller and committee members, Dr. Otto Berg, and Dr. John Constable. I thank them for championing me as their graduate student and for helping me navigate through the process of becoming a scientist. Their scientific knowledge can only be surpassed by their support and encouragement and they were an integral part in my development as a scientist. I also appreciate Darius Khorshidchehr, David Ryan, Eshan Bhardwaj, Janneke Schwaner, Maxwell Hall, Nolan Avery, and Rayhan Kabir for their guidance and encouragement. Thank you Dr. Roi Holzman for your collaboration with us at the beginning of this project, for sharing your research experience on suction feeding, and for your expertise on PIV software. Thank you Dr. Steven Vogel for attending my first oral presentation at SICB; your presence made it a transcendent experience, and it will be something that I hold dear. I would also like to thank my parents; without them, none of this would be possible. To me this research represents not only a pursuit of knowledge toward understanding the world around us but also shows what can be achieved when great people collaborate and work together. TABLE OF CONTENTS Page LIST OF TABLES .............................................................................................. vi LIST OF FIGURES ........................................................................................... vii INTRODUCTION ............................................................................................... 1 Suction Feeding – An Overview .................................................................. 1 Suction Feeding Mechanics in Adult Fish .................................................. 2 Suction Feeding – Effects of Flow Regime .................................................. 3 Research Objectives, Aims and Hypothesis ................................................ 5 MATERIALS & METHODS ............................................................................... 7 Plant Husbandry .......................................................................................... 7 Experimental Set-Up to Record Feeding Strikes ....................................... 9 Data Analysis ............................................................................................. 13 RESULTS .......................................................................................................... 16 Plant Morphology ....................................................................................... 16 Time Line of Suction Events ..................................................................... 17 Flow Generated During Suction Events ................................................... 19 DISCUSSION .................................................................................................... 22 Comparison with Published Studies ......................................................... 22 Main Conclusions and Future Directions ................................................. 24 REFERENCES .................................................................................................. 25 APPENDICES ................................................................................................... 28 APPENDIX A: INDEX OF KINEMATICS RECORDINGS ............................ 29 APPENDIX B: INDEX OF FLOW RECORDINGS .......................................... 41 LIST OF TABLES Page Table 1 . Event during a suction event of Utricularia vulgaris versus Utricularia gibba . ................................................................................ 19 Table 2 . Flow speeds and duration of the suction event determined by flow visualization for Utricularia vulgaris versus Utricularia gibba . ................................................................................................... 21 LIST OF FIGURES Page Figure 1 : Suction-feeding performance is determined by prey properties, predator traits, and their interactions (after Holzman et al., 2012). .......... 3 Figure 2 : Photograph of a bladderwort strand ( Utricularia vulgaris ). .................... 4 Figure 3 : Left: Photograph of a bladderwort trap ( Utricularia gibba ). Right: schematic drawing of the trap. .................................................................. 5 Figure 4 : Zooplankton being filtered from the CSU Fresno pond. ......................... 9 Figure 5 : The Phantom V12.1 high-speed camera (right). .................................... 10 Figure 6 : Schematic top view of the macro photography stage (not to scale). ..... 12 Figure 7 : Definition of gape (diameter of the mouth opening), funnel diameter (funnel only present in U. gibba), and bladder size (longest dimension of the trap). ............................................................................ 13 Figure 8 : Spatial and time transects through the suction flow of a Utricularia gibba . ...................................................................................................... 15 Figure 9 : Morphology of U. vulgaris (left) versus U. gibba (right). ..................... 17 Figure 10 : Time line of a suction event for U. gibba (left) and U. vulgaris (right). All time and flow speed values are averages. ............................ 18 Figure 11 : Representative time transect of flow speed at half gape from the mouth for U. gibba (top) and U. vulgaris (bottom). ............................... 20 INTRODUCTION Suction Feeding – An Overview Suction feeding is a common mechanism of prey capture used by many aquatic organisms and is the most common feeding mechanism in fish. The hydrodynamics of suction feeding have been studied extensively for decades. The focus of this research has been on adult fish, who have maximum gape sizes of 3 mm or greater (Holzman et al., 2008). There is much less experimental research on small suction feeders, such as larval fish, tadpoles, and bladderworts, who have gape sizes of 0.2 to 0.5 mm (Drost et al., 1988; Deban and Olsen, 2002; China and Holzman, 2014). Yet size is an important aspect of flow phenomena, including suction feeding, because flow phenomena strongly depend on size; in the case of suction feeding this is gape size. The relationship between fluid mechanics and size is formally described