DIET SELECTION IN THE YELLOW-BELLIED SLIDER TURTLE, TRACHEMYS SCRIPTA: ONTOGENETIC DIET SHIFTS AND ASSOCIATIVE EFFECTS BETWEEN ANIMAL AND PLANT DIET ITEMS By SARAH S. BOUCHARD A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2004 Copyright 2004 by Sarah Bouchard This dissertation is dedicated to my father, Thomas Bouchard. ACKNOWLEDGMENTS I thank my advisor, Karen Bjorndal, as well as my committee members, Lauren Chapman, Nat Frazer, Carmine Lanciani, and Doug Levey, for their invaluable support and guidance throughout this study. I also thank Alan Bolten who provided valuable assistance in the beginning stages of this work. I am extremely indebted to the following undergraduate research assistants whose hard work and willingness to do almost anything made this project possible: Craig Baker, Lindy Barrow, Ann Frial, Jennifer Hill, Rachel Marcus, Natalie Marshall, and Carrie Newsom. Additionally, I am grateful to Paul Coehler, Dan Connelly, Justin Congdon, and Bill Hopkins who assisted with the collection of turtles by providing equipment and access to ponds. Jim Watt also assisted by providing juvenile turtles from his turtle farm in Pt. Mayaka, Florida. David Chynoweth, Kaoru Kitajima, Adegbola Adesogan, and David Hodell graciously allowed me to conduct analyses in their laboratories at the University of Florida, and Colin Chapman, Jason Curtis, Patrick Haley, Nathan Kreuger, Frank Robbins, and Karyn Rode provided invaluable assistance with these analyses. Kavita Isvaran, Suhel Quader, and Nat Seavy offered much appreciated statistical advice, and Joe Carlin provided constructive comments on earlier versions of these papers. I also thank the graduate students, post docs, and faculty in the Department of Zoology for providing intellectual and emotional support throughout my graduate career. In particular, I would like to acknowledge Sophia Balcomb, Rico Holdo, Carlos Iudica, Yolanda Leon, Yoshi Matsuzawa, Shannon McCauley, Alison McCombe, Ben Miner, iv Kate Moran, Daphne Onderdonk, John Paul, Peter Piermarini, Greg Pryor, April Randle, Kim Reich, Brian Riewald, Sarah Schaack, Jeff Seminoff, Laura Sirot, Mark Spritzer, Manjula Tiwari, James Vonesh, and Amy Zanne. Finally, I am extremely grateful to my husband, Cotton Randall, and my parents, Tom and Muriel Bouchard. Their constant support and encouragement allowed me to persevere through the ups and downs associated with this dissertation. Funding for this work came from the Archie Carr Center for Sea Turtle Research, Brian Riewald Memorial Fund, Chelonian Research Foundation, McLaughlin Dissertation Fellowship, Sigma Xi, Society for the Study of Reptiles and Amphibians, and the University of Florida Women’s Club. The Institutional Animal Care and Use Committee at the University of Florida approved this research. v TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES........................................................................................................... viii LIST OF FIGURES .............................................................................................................x ABSTRACT....................................................................................................................... xi CHAPTER 1 INTRODUCTION ........................................................................................................1 2 ONTOGENETIC DIET SHIFTS AND DIGESTIVE CONSTRAINTS IN THE YELLOW-BELLIED SLIDER TURTLE, TRACHEMYS SCRIPTA ..........................5 Introduction...................................................................................................................5 Methods ........................................................................................................................9 Experimental Animals and Diets...........................................................................9 Experimental Protocol.........................................................................................10 Nutrient Analyses ................................................................................................12 Digestive Processing Calculations ......................................................................14 Juvenile Growth and Composition ......................................................................15 Results.........................................................................................................................16 Discussion...................................................................................................................17 Juvenile Growth and Composition ......................................................................17 Digestive Processing ...........................................................................................18 Conclusions.................................................................................................................21 3 ASSOCIATIVE EFFECTS BETWEEN ANIMAL AND PLANT DIET ITEMS IN THE YELLOW-BELLIED SLIDER TURTLE, TRACHEMYS SCRIPTA ................26 Introduction.................................................................................................................26 Methods ......................................................................................................................30 Experimental Animals and Diets.........................................................................30 Experimental Protocol.........................................................................................32 Nutrient Analyses ................................................................................................33 Digestive Processing Calculations ......................................................................35 vi Short-Chain Fatty Acid Concentrations ..............................................................37 Results.........................................................................................................................38 Feeding Trials with Adult Turtles .......................................................................38 Feeding Trials with Juvenile Turtles ...................................................................40 Discussion...................................................................................................................41 Conclusions.................................................................................................................45 4 MICROBIAL FERMENTATION IN JUVENILE AND ADULT YELLOW- BELLIED SLIDER TURTLES, TRACHEMYS SCRIPTA.........................................58 Introduction.................................................................................................................58 Methods ......................................................................................................................60 Results.........................................................................................................................62 Discussion...................................................................................................................63 5 EFFECT OF DIET ON GASTROINTESTINAL TRACT MORPHOLOGY IN THE YELLOW-BELLIED SLIDER TURTLE, TRACHEMYS SCRIPTA.........................71 Introduction.................................................................................................................71 Methods ......................................................................................................................73 Results and Discussion ...............................................................................................74 6 CONCLUSIONS ........................................................................................................79 APPENDIX DIGESTIVE PROCESSING OF DRY MATTER BY ADULT TURTLES.....................82 LIST OF REFERENCES...................................................................................................86 BIOGRAPHICAL SKETCH .............................................................................................95 vii LIST OF TABLES Table page 2-1 Nutrient composition of duckweed and shrimp diets fed to juvenile and adult turtles as well as nutrient composition of orts (remaining food) for each treatment...................................................................................................................23 2-2 Digestive processing of duckweed and shrimp diets fed to juvenile and adult turtles........................................................................................................................24 2-3 Growth and nutrient composition of juvenile turtles fed duckweed or shrimp........25 3-1 Summary of studies investigating associative effects in wildlife. ...........................47 3-2 Nutrient composition of duckweed and shrimp fed to adult turtles .........................48 3-3 Nutrient composition of duckweed and shrimp fed to juvenile turtles ....................49 3-4 Nutrient composition of duckweed and shrimp orts (remaining food) from feeding trials with adults ..........................................................................................50 3-5 Digestive processing of duckweed, shrimp, and mixed diets by adult T. scripta ....51 3-6 Differences between actual and predicted digestibilities, digestible intakes, and daily gains of adult turtles