Secondary Plant Compounds as Feeding Deterrents in the African Subterranean Termite Schedorhinotermes lamanianus Sjöstedt (Isoptera: Rhinotermitidae): A Behavioural and Neurophysiological Approach Inaugural-Dissertation zur Erlangung des Doktorgrades der Fakultät Biologie, Chemie und Geowissenschaften der Universität Bayreuth vorgelegt von Dipl.-Biol. Univ. Stefan Groß aus Riesa Bayreuth, im April 2010 Die vorliegende Arbeit wurde in der Zeit von März 2005 bis April 2010 am Lehrstuhl Tierphysiologie der Universität Bayreuth unter der Betreuung von Herrn Prof. Dr. Dietrich von Holst und Dr. Manfred Kaib angefertigt. The present study was conducted from March 2005 until April 2010 at the Department of Animal Physiology of the University of Bayreuth under the supervision of Prof. Dr. Dietrich von Holst and Dr. Manfred Kaib. Vollständiger Abdruck der von der Fakultät für Biologie, Chemie und Geo- wissenschaften der Universität Bayreuth genehmigten Dissertation zur Erlangung des akademischen Grades Doktor der Naturwissenschaften (Dr. rer. nat.). Amtierender Dekan: Prof. Dr. Stephan Clemens Promotionsgesuch eingereicht am: 20. April 2010 Zulassung durch die Prüfungskommission: 28. April 2010 Tag des wissenschaftlichen Kolloquiums: 30. Juli 2010 Prüfungsausschuß : Prof. Dr. Dietrich von Holst (Erstgutachter) Prof. Dr. Klaus H. Hoffmann (Zweitgutachter) Prof. Dr. Stephan Clemens (Vorsitzender) Prof. Dr. Stefan Schuster Prof. Dr. Karlheinz Seifert Acknowledgements ••• I thank Prof. Dr. Dietrich von Holst, who gave me the opportunity to carry out this Ph.D. project at the Department of Animal Physiology, for his great interest in the progress of this project and helpful discussions about this thesis. ••• Many thanks to Dr. Manfred Kaib, who gave me the opportunity to do this project in his lab group. I am very grateful for his great interest in the progress of this project, his great help and the many helpful discussions about the experimental approaches and results. ••• I thank Prof. Dr. Stefan Schuster as new head of the Department of Animal Physiology, who gave me the opportunity to finish my thesis at his department. ••• Special thanks to Prof. Dr. Karlheinz Seifert and Prof. Dr. Michael Wink (University of Heidelberg) for kindly providing most of the alkaloids used in the present study. ••• Many thanks to the whole lab group "Kaib" (Dr. Florian Lengyel, Dr. Sebastian Klaus, Carolin Radzka, Sandra Wetzel, Maximiliane Schumm, Franziska Wende) for the kind atmosphere in the lab and the helpful discussions. Special thanks to Antje Halwas for her help with the lab work, the interesting discussions and the provision of "energy carriers". I thank Anna Rädlein and Tanja Spörlein for their great help during the behavioural experiments. ••• I thank the German Science Foundation (Deutsche Forschungsgemeinschaft) for financial support of this project within the Graduate College 678: Ecological Significance of Natural Compounds and other Signals in Insects – from Structure to Function and the head of the graduate college Prof. Dr. Klaus H. Hoffmann for his great interest in the progress of the project . ••• Many thanks to all old and new members of the Department of Animal Physiology for the kind atmosphere at work, especially Dr. Heiko Rödel, Dr. Anett Starkloff, and Kerstin Schunke for the helpful discussions and the nice time in our office. ••• I thank Dr. Christine Geier and Dr. Sabine Gerstner for being very good "lab neighbours" and the joyful lunch times over the last years. ••• Many thanks to Petra, Tassilo, Lesley and Ryan for being very good friends and keeping me sane during stressful times. ••• Last but not least, I am very grateful to my parents, who always believed in me and for their great moral and financial support over the last twelve years. Für meine Eltern TABLE OF CONTENTS 1 INTRODUCTION .....................................................................................1 1.1 Host Plant Recognition and Feeding Behaviour................................................. 2 1.2 Host Plant Recognition and Chemosensory Input System ................................ 4 1.3 Aims of the Thesis.................................................................................................. 7 2 DEFINITIONS AND ABBREVIATIONS ......................................................9 3 MATERIALS AND METHODS ...............................................................11 3.1 General ................................................................................................................. 11 3.1.1 The Focus Species Schedorhinotermes lamanianus (Sjöstedt) ..................... 11 3.1.2 Laboratory Colonies........................................................................................ 11 3.2 Secondary Plant Compounds ............................................................................. 13 3.3 Behavioural Investigations ................................................................................. 16 3.3.1 Filter Paper Choice Test ................................................................................. 16 3.3.1.1 Experimental Design .......................................................................................................16 3.3.1.2 Data Analysis...................................................................................................................17 3.3.2 Filter Paper No-Choice Test........................................................................... 17 3.3.2.1 Experimental Design .......................................................................................................17 3.3.2.2 Data Analysis...................................................................................................................18 3.3.3 Wooden Cube Choice-Test I – Single Choice................................................ 19 3.3.3.1 Experimental Design .......................................................................................................19 3.3.3.2 Data Analysis...................................................................................................................20 3.3.4 Wooden Cube Choice Test II – Multiple Choice .......................................... 20 3.3.4.1 Experimental Design .......................................................................................................21 3.3.4.2 Data Analysis...................................................................................................................23 3.4 Neurophysiological Investigations ..................................................................... 24 3.4.1 Tip-Recording Technique............................................................................... 24 3.4.1.1 General ............................................................................................................................24 3.4.1.2 Experiments.....................................................................................................................27 3.5 Statistics................................................................................................................ 29 I 4 RESULTS .............................................................................................30 4.1 Food Choice and Food Consumption ................................................................ 30 4.1.1 Threshold for Avoidance in a Single Choice Situation ................................ 30 4.1.2 Food Consumption .......................................................................................... 31 4.1.2.1 Quantitative Food Consumption on Filter Paper in a No-Choice Situation ...................31 4.1.2.2 Quantitative Food Consumption on Wood in a Single Choice Situation .......................33 4.1.2.3 Quantitative Food Consumption on Wood in a Multiple Choice Situation....................35 4.2 Neurophysiological Investigations ..................................................................... 39 4.2.1 The TP II Sensillum and Alkaloids................................................................ 39 4.2.1.1 Concentration-Reponse Relationships ............................................................................39 4.2.1.2 Cross-Adaptation Tests at the TP II Sensillum ...............................................................47 4.2.2 TP I Sensillum and Feeding Deterrent Alkaloids......................................... 58 4.2.2.1 Concentration-Response Relationships...........................................................................58 4.2.3 TP II Sensillum and Feeding Deterrent Non-Alkaloids............................... 61 4.2.3.1 Concentration-Response Relationships...........................................................................61 4.2.4 TP I Sensillum and Feeding Deterrent Non-Alkaloids................................. 62 4.2.4.1 Concentration-Response Relationships...........................................................................62 5 DISCUSSION ........................................................................................63 5.1 Effects of Secondary Compounds on Feeding Behaviour................................ 63 5.1.1 Effects of Alkaloids on Feeding Behaviour ................................................... 64 5.1.2 Effects of Non-Alkaloids on Feeding Behaviour........................................... 68 5.2 Neural Input for Feeding Deterrents................................................................. 73 5.2.1 Recognition of Alkaloids................................................................................