Ökologie und Paarungsverhalten des Regenwurms Lumbricus terrestris in Zusammenhang mit Parasitenbefall durch Monocystis sp. Dissertation der Mathematisch-Naturwissenschaftlichen Fakultät der Eberhard Karls Universität Tübingen zur Erlangung des Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) vorgelegt von Dipl. Biol. Susanne Weller aus Aachen Tübingen 2013 Tag der mündlichen Qualifikation: 10.04.2013 Dekan: Prof. Dr. Wolfgang Rosenstiel 1. Berichterstatter: Prof. Dr. Nico Michiels 2. Berichterstatter: Prof. Dr. Katharina Foerster Table of Content – Overview I. OVERVIEW ................................................................................ 1 II. GENERAL INTRODUCTION .................................................... 4 III. PARASITE-MEDIATED PRECOPULATORY MATE CHOICE IN A SIMULTANEOUS HERMAPHRODITE ............................... 17 IV. MULTI-TRAIT ASSORTATIVE MATING IN A SIMULTANEOUS HERMAPHRODITE ....................................... 56 V. DEMOGRAPHIC AND INFECTION PATTERNS IN A LUMBRICID-GREGARINE SYSTEM UNDER ORGANIC AND NO TILLAGE MANAGEMENT .......................................................... 89 VI. LITERATURE ...................................................................... 115 VII. ACKNOWLEDGEMENTS ................................................... 141 VIII. ERKLÄRUNG UND EIGENANTEIL ................................... 143 Table of Content – in detail I. OVERVIEW ......................................................... 1 SUMMARY OF DISSERTATION ........................................................................... 1 OUTLINE OF THE THESIS .................................................................................. 1 ZUSAMMENFASSUNG DEUTSCH ........................................................................ 2 II. GENERAL INTRODUCTION .............................. 4 SEXUAL SELECTION AND PARASITISM ................................................................ 4 Definition of mate choice .......................................................................... 4 Anisogamy as primary source for sexual selection ................................... 4 Mechanisms and levels of sexual selection .............................................. 5 Host-parasite coevolution and sexual reproduction .................................. 7 HERMAPHRODITISM AND MATE CHOICE ............................................................. 8 Evolution and varieties of hermaphroditism .............................................. 8 Mate choice in hermaphrodites ................................................................. 8 THE SYSTEM UNDER INVESTIGATION ................................................................. 9 Lumbricus terrestris .................................................................................. 9 Monocystis .............................................................................................. 13 OBJECTIVES OF THIS THESIS .......................................................................... 15 III. PARASITE-MEDIATED PRECOPULATORY MATE CHOICE IN A SIMULTANEOUS HERMAPHRODITE .............................................. 17 ABSTRACT .................................................................................................... 17 INTRODUCTION ............................................................................................. 18 Parasite-mediated sexual selection ........................................................ 18 Sexual selection in hermaphrodites ........................................................ 20 The system under investigation .............................................................. 23 Hypothesis & Expectations ..................................................................... 25 MATERIALS AND METHODS ............................................................................ 27 Raising uninfected worms ....................................................................... 27 Controlled infection ................................................................................. 27 Observation of pairs ................................................................................ 30 Quantification of infection ....................................................................... 31 Reproductive Output ............................................................................... 32 Video analysis ......................................................................................... 32 Colour analysis ....................................................................................... 33 Data analysis .......................................................................................... 36 Successful Infection ................................................................................ 36 Extraordinary mating behaviour .............................................................. 37 RESULTS ...................................................................................................... 39 Parasite costs on male and female reproductive functions ..................... 39 Parasites influence mating behaviour ..................................................... 40 Spectral measurements, Monocystis infection and time effects.............. 43 Could earthworms use colours as indirect mate choice criteria? ............ 46 DISCUSSION ................................................................................................. 49 Parasite costs on male and female reproduction .................................... 49 Parasite-mediated mate choice in L. terrestris ........................................ 50 Table of Content – in detail Optimal mating rates and remote copulations in L. terrestris .................. 51 How can earthworms perceive parasitism in their mates? ...................... 52 Which sex exhibits choice? – Sex allocation and parasitism .................. 54 Conclusion .............................................................................................. 55 IV. MULTI-TRAIT ASSORTATIVE MATING IN A SIMULTANEOUS HERMAPHRODITE ................. 56 ABSTRACT .................................................................................................... 56 INTRODUCTION ............................................................................................. 57 Mate choice – gathering evidence in gonochoristic species ................... 57 Setting up hermaphrodites- a challenge ................................................. 58 Lumbricus terrestris – a special hermaphrodite ...................................... 59 Hypothesis .............................................................................................. 60 MATERIALS AND METHODS ............................................................................ 62 Experimental set up ................................................................................ 62 Video analysis ......................................................................................... 63 Spectral analysis ..................................................................................... 63 Χ2 ............................................................................................................ 64 Dissection ............................................................................................... 65 Parasite & sperm count .......................................................................... 65 Statistical procedures ............................................................................. 65 Assortative mating .................................................................................. 68 RESULTS ...................................................................................................... 73 Costs of Parasitism: Effect on sperm concentration ............................... 73 Costs of parasitism: Effect on growth ..................................................... 73 Parasite effects on spectral traits ............................................................ 74 Mating distances - Minimizing the pull out risk ........................................ 75 Assortative mating .................................................................................. 76 Group behaviour ..................................................................................... 79 DISCUSSION ................................................................................................. 82 Assortative mating .................................................................................. 82 Costs of Parasitism ................................................................................. 83 Colour, parasitism and mate choice ........................................................ 84 Do earthworms combine traits to choose their partner? ......................... 84 Group behaviour ..................................................................................... 85 Mating distance ....................................................................................... 86 Conclusion .............................................................................................. 86 APPENDIX .................................................................................................... 87 V. DEMOGRAPHIC AND INFECTION PATTERNS IN A LUMBRICID-GREGARINE SYSTEM UNDER ORGANIC AND NO TILLAGE MANAGEMENT .. 89 ABSTRACT .................................................................................................... 89 INTRODUCTION ............................................................................................