POTENTIAL THREATS OF THE EXOTIC APPLE SNAIL POMACEA INSULARUM TO AQUATIC ECOSYSTEMS IN GEORGIA AND FLORIDA by SHELLEY MARIE ROBERTSON (Under the Direction of Susan Bennett Wilde) ABSTRACT The Island apple snail, Pomacea insularum is a freshwater gastropod in the family Ampullaridae. It was introduced into the United States via the aquarium trade approximately 30 years ago and now has established reproducing populations in at least seven southeastern states. It is a highly invasive species with high rates of reproduction and consumption of native aquatic vegetation. A survey of reported Georgia populations confirmed that there are at least ten individual occurrences of exotic apple snails in the state, and that they have not reached their equilibrium distribution. We also investigated the ability of P. insularum to harbor a cyanotoxin that may be detrimental to its avian predator in Florida, the endangered Florida snail kite (Rostrhamus sociabilis). The invasive P. insularum transferred the undescribed cyanotoxin associated with Avian Vacuolar Myelinopathy to domestic chickens in a laboratory feeding study. INDEX WORDS: apple snail, Pomacea insularum, invasive species, Avian Vacuolar Myelinopathy, AVM, Florida snail kite, Rostrhamus sociabilis, Hydrilla verticillata POTENTIAL THREATS OF THE EXOTIC APPLE SNAIL POMACEA INSULARUM TO AQUATIC ECOSYSTEMS IN GEORGIA AND FLORIDA by SHELLEY MARIE ROBERTSON BS, University of Georgia, 2006 AB, University of Georgia, 2007 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2012 © 2012 Shelley Marie Robertson All Rights Reserved POTENTIAL THREATS OF THE EXOTIC APPLE SNAIL POMACEA INSULARUM TO AQUATIC ECOSYSTEMS IN GEORGIA AND FLORIDA by SHELLEY MARIE ROBERTSON Major Professor: Susan B. Wilde Committee: James E. Byers Brett Albanese Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2012 ACKNOWLEDGEMENTS Many thanks to my advisor, Dr. Susan Wilde, for all your support and advice. Your sense of humor, adventurousness and experience have made my graduate school experience fun, eye- opening and of course educational. I would like to offer my tremendous appreciation to Drs. Jay Shelton and Rhett Jackson for helping to prepare me to become a successful graduate student and field scientist by involving me in a wide diversity of projects during my time as hydrology lab tech, and for continuing to advise and support me as I moved on to grad school. Thank you to Dr. Brett Albanese for serving on my committee and for hiring me as a TA for the most amazing and intense class that UGA has to offer, your enthusiasm for fishes is truly contagious. Thanks also to Dr. Jeb Byers for serving on my committee. A million thanks to Dr. Becca Haynie, I couldn’t have done it without your support and expertise. Thanks for editing or listening to everything I have ever written or presented, for driving around south Georgia with me in a huge white van, and for teaching me how to live in Africa. Thank you for the assistance and sympathies of my current and former lab mates, Jamie Morgan, Brigette Haram, Jenny Garrison, Ridwan Bhuiyan and most of all James Herrin, whose enthusiasm for research of any kind has taught me that any lab or field project is possible and you don’t (always) have to get it right on the first try. Finally thank you Carter for your love and support through all the years it has taken me to finally find an enjoyable and exciting career path, and I’m so grateful that it gave us a reason to stay in our favorite city a little while longer. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ........................................................................................................... iv LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ..................................................................................................................... viii CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW ....................................................1 Invasive Apple Snails ..............................................................................................1 Objectives and Justification ....................................................................................5 References ...............................................................................................................6 2 THE DISTRIBUTION OF THE EXOTIC APPLE SNAIL POMACEA INSULARUM IN GEORGIA ...............................................................................................................9 Abstract ..................................................................................................................10 Introduction ............................................................................................................10 Methods..................................................................................................................14 Results and Individual Site Assessments ...............................................................17 Discussion ..............................................................................................................30 Conclusions ............................................................................................................35 References .............................................................................................................39 3 ALTERNATE FOOD-CHAIN TRANSFER OF THE BIOTOXIN LINKED TO AVIAN VACUOLAR MYELINOPATHY (AVM) ....................................................43 v Abstract ..................................................................................................................44 Introduction ............................................................................................................45 Methods..................................................................................................................48 Results ....................................................................................................................52 Discussion ..............................................................................................................54 References ..............................................................................................................59 4 CONCLUSIONS..........................................................................................................62 References ..............................................................................................................65 vi LIST OF TABLES Page Table 2.1: Experimentally determined incipient physiological tolerance limits for adult and juvenile Pomacea insularum collected in Texas .........................................................14 Table 2.2: Summer 2011 field sampling locations ........................................................................15 Table 2.3: Summer 2011 field survey sites and current status of IAS populations .......................19 Table 2.4: Water quality measurements for all sites visited during 2011 IAS survey ...................29 Table 2.5: Monitoring recommendations based on results of 2011 IAS survey ............................37 Table 2.6: Aquatic plant community assessment data from 2011 surveys ....................................38 Table 3.1: Groups and diets of chickens in laboratory feeding trials ............................................51 Table 3.2: Results of histological analysis of brain section slides from feeding trials ..................53 vii LIST OF FIGURES Page Figure 2.1: Current U.S. distribution of Pomacea insularum ........................................................12 Figure 2.2: Adult P. insularum laying eggs ...................................................................................13 Figure 2.3: 2011 confirmed IAS populations in southern Georgia ................................................18 Figure 2.4: IAS egg masses on cattails at St. Mary’s Aquatic Center Pond ..................................20 Figure 2.5: Fire ant predation of IAS eggs at St. Mary’s Aquatic Center Pond ............................21 Figure 2.6: Japanese mystery snail (Cipangopaludina japonica) shells collected at the Savannah River at Jackson, SC in April 2012 ..............................................................................24 Figure 2.7: IAS egg mass on the main channel of the Ochlockonee River above Thomasville ....26 Figure 2.8: Lake Seminole IAS sighting locations ........................................................................28 Figure 2.9: Retaining wall in front of a residence on the southern side of the Flint River Arm of Lake Seminole covered with IAS egg masses on September 9, 2011 .........................28 Figure 2.10: USDA Plant Hardiness zones for Georgia ................................................................31 Figure 3.1: (a) Light micrograph of optic tectum and optic lobe (40x) of chicken fed control snail material. (b) Light micrograph of optic tectum and optic lobe (40x) of chicken fed treatment snail material. ...............................................................................................53 Figure 3.2: (a) Light micrograph of cerebellum (40x) of chicken fed control snail material. (b) Light micrograph of cerebellum (40x) of chicken fed treatment snail material ..........53 Figure 3.3:
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