ABSTRACT DEVELOPING A MECHANICAL MODEL OF A SUCTION FEEDER Suction feeding is a common feeding mode in macroscopic aquatic organisms and the dominant feeding mode in fish. In contrast, microscopic aquatic organisms do not use suction feeding. In fact, the smallest known suction feeders are fish larvae and bladderwort, a genus of carnivorous plants that catches zooplankton in underwater traps, both of which have gapes around 200 microns in diameter. Experimental and theoretical studies of suction feeding have shown that the ability to generate a steep spatial pressure gradient correlates strongly with capture success. Those studies also show that suction feeding is essentially an inertial process and therefore will be effective only if viscous fluid forces can be neglected, which is as long as the gape is large enough and the suction flow (i.e. the negative pressure gradient near the mouth) fast enough to minimize the relative effects of friction. Our current understanding of the hydrodynamics of suction feeding suggests that suction feeding is not effective in small organisms. In fact, both mathematical models of suction feeding, and experimental observations of larval fish suggest that their gape of 200 microns is near the lower size limit of suction feeding and that their suction flows generated by a 0.2 kPa pressure differential are too weak to ensure prey capture. In this project, we explored the lower size limit of suction feeding by characterizing the suction flows of bladderwort and salamanders and using the data collected to develop a robotic model of a suction feeder. Fatima Hidalgo May 2018 DEVELOPING A MECHANICAL MODEL OF A SUCTION FEEDER by Fatima Hidalgo 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 2018 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. Fatima Hidalgo Thesis Author Ulrike Müller (Chair) Biology Otto Berg Chemistry Stephen Deban University of South Florida, Integrative 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 thank my advisor and mentor Dr. Ulrike Müller for not letting me quit and knowing where I could focus for my project. I would also like to thank Dr. Otto Berg and Dr. Stephen Deban for the support given as committee members and during the research process. I would also like to thank my fellow lab mates; Ray Kabir, Nolan Avery, Andrea Aparicio Ramirez, Max Hall and Mohammed Shaik. I would also like to acknowledge the help provided by the Deban lab at University of South Florida, especially Dr. Charlotte Stinson. I would like to recognize the support of my family, friends and shipmates that have been by my side during this journey. Lastly, I would like to acknowledge the funding from Bridges to Doctorate program, National Science Foundation, and Sally Casanova Pre-Doctoral Scholarship that has allowed me to present this research and supported me. TABLE OF CONTENTS Page LIST OF TABLES .................................................................................................. vi LIST OF FIGURES ................................................................................................ vii INTRODUCTION .................................................................................................... 1 Background ....................................................................................................... 1 Suction Feeding in Organisms .......................................................................... 1 Morphology of Suction Feeders ........................................................................ 3 Aims and Objectives ....................................................................................... 15 METHODS AND MATERIALS ........................................................................... 17 Husbandry ....................................................................................................... 17 Morphological Measurements of Lab Grown Bladderworts .......................... 17 Selecting Bladderwort for High Speed Filming .............................................. 18 High Speed Filming of Feeding Event ............................................................ 19 Data Analysis .................................................................................................. 20 Building and Operation of a Mechanical Suction Feeder ............................... 21 RESULTS ............................................................................................................... 25 Characterizing the Suction Feeding Morphology and Motion of Bladderwort and Salamanders ............................................................. 25 Characterizing the Suction Feeding Flows of Bladderwort and Salamander ........................................................................................... 28 Building a Mechanical Model of a Suction Feeder ........................................ 31 DISCUSSION ......................................................................................................... 33 REFERENCES ....................................................................................................... 38 APPENDIX: LITERATURE DATA ..................................................................... 44 LIST OF TABLES Page Table 1 Gape Diameters of Suction Feeders .................................................. 25 Table 2 Time to Peak Gape (TTPG) of Suction Feeders ................................ 27 Table 3 Flow Characterization of Suction Feeders ....................................... 28 Table 4 Scaling Parameters ........................................................................... 32 LIST OF FIGURES Page Figure 1. Images showing maximum hyobranchial expansion of aquatic feeding salamanders and their respective clear and stained hyobranchial apparatus. .................................................................................................. 5 Figure 2. Diagram of the hyobranchial apparatus of G. porphyriticus. ................. 6 Figure 3. From Poppinga et al., 2016 – Figure 1. “General bladderwort morphology, depicted exemplarily by U. vulgaris. .................................. 8 Figure 4. From Poppinga et al. (2016) – Figure 2. “Lateral view of different trap types, indicating the position of the trap entrance (te) and of the stalk (st) ..................................................................................................... 9 Figure 5. From Poppinga et al. 2016 – Figure 5. Morphology of the trap body ... 11 Figure 6. Developing flow through entrance of a pipe. ......................................... 14 Figure 7. Linear motor controller and power supplies. .......................................... 22 Figure 8. Linear motor with slider. ........................................................................ 23 Figure 9. Gantry crane schematic that was sent from Numatic engineering. ........ 23 Figure 10. Graph showing how body length scales to gape diameter. .................. 26 Figure 11. Graph showing how body length scales with time to peak gape for U. praelonga, Ambystoma sp., G. porphyriticus, and fish. ............... 27 Figure 12. Graph showing the scaling coefficient of U. praelonga, Ambystoma sp., and G. porphyriticus. .................................................... 29 Figure 13. Still shot from particle tracking video of G, porphyriticus showing path particles traveled. .............................................................. 29 Figure 14. Still shot of from particle tracking video of Ambystoma sp. showing path particles traveled ............................................................... 30 Figure 15. Still shot of U. praelonga showing path particles traveled .................. 30 Figure 16. Graph showing time to peak gape, peak flow, and gape vs body for bladderwort, fish at different life stages, and salamanders. ..... 37 INTRODUCTION Background Organisms have various modes of feeding. Using suction is a mode that various aquatic organisms use to get nutrients and energy. Suction feeding is done by larval fish, adult fish, larval salamanders, adult salamanders, and some carnivorous plants. Suction can be drawn by an organism in various ways. One of the ways is by having a difference between the internal pressure and the environmental pressure. The differential pressure is established through stored elastic energy. The other way that suction can occur is by expanding the internal volume, which can be done by changing the volume of the buccal area. This movement of the buccal area is produced by kinematic energy. Both of these methods exert forces upon the prey and cause them to be entrained with the fluid that is being sucked into the organism’s mouth. In this study we looked at suction feeding