Dissertation zur Erlangung des naturwissenschaftlichen Doktorgrades der Bayerischen Julius-Maximilians-Universität Würzburg vorgelegt von Jürgen Paul aus Nürnberg Würzburg 2001 THE MOUTHPARTS OF ANTS - Contents p. II - Contents General Introduction .......................................................................................................... 1 A. THE MANDIBLES A.1. Review: Mandible movements in ants ................................................................. 5 Introduction .................................................................................................................... 6 Muscle fiber types of the mandible closer muscle ......................................................... 7 Muscle fiber composition reflects adaptive differences among species ........................ 8 Trap-jaw mechanism yields maximum velocity ........................................................... 12 A.2. Optimizing force and velocity: Mandible muscle fiber attachments in ants ..................................................... 15 Introduction .................................................................................................................. 16 Materials and Methods ................................................................................................. 18 Results .......................................................................................................................... 18 - Composition of the apodeme ................................................................................... 20 - Positions and attachment angles of different fiber types ......................................... 23 Discussion .................................................................................................................... 25 - Apodeme design: force and velocity require different angles of attachment .......... 25 - Muscle fiber attachment: why apodeme filaments? ................................................ 28 - Species-specific differences: filaments or direct fiber attachment? ........................ 30 Appendix ...................................................................................................................... 32 - Model 1: optimal angle of attachment to maximize power output .......................... 32 - Model 2: efficient use of head capsule volume and the mode of fiber attachment .. 33 A.3. Motor control of the mandible closer muscle in ants .................................... 35 Introduction .................................................................................................................. 36 Materials and Methods ................................................................................................. 38 - Electrophysiology .................................................................................................... 38 - Mandible movements .............................................................................................. 39 - Neuroanatomy ......................................................................................................... 40 Results .......................................................................................................................... 40 - Muscle fiber groups and motor units ....................................................................... 40 - Force and velocity of mandible movements ............................................................ 44 - Neuroanatomy ......................................................................................................... 48 Contents - p. III Discussion .................................................................................................................... 51 - Motor units and their input regions ......................................................................... 51 - Modulation and multineuronal innervation ............................................................. 53 - Force and velocity of mandible movements ............................................................ 55 B. THE LABIOMAXILLARY COMPLEX B.4. How do ants put out their tongue? ..................................................................... 57 Introduction .................................................................................................................. 58 Materials and Methods ................................................................................................. 59 - Histology ................................................................................................................. 60 - Morphometry ........................................................................................................... 60 - ATP-experiments ..................................................................................................... 60 Results .......................................................................................................................... 61 - Anatomical design ................................................................................................... 61 - Muscle morphology ................................................................................................. 65 - Glossa protraction mechanism ................................................................................ 69 Discussion .................................................................................................................... 73 - Anatomical design ................................................................................................... 73 - Non muscular movement mechanisms .................................................................... 75 B.5. Liquid food intake in ants: I. Feeding techniques and intake rates ........... 79 Introduction .................................................................................................................. 80 Materials and Methods ................................................................................................. 82 Results .......................................................................................................................... 83 - Feeding techniques .................................................................................................. 83 - Intake rates and ant size ........................................................................................... 85 - Interspecific comparison .......................................................................................... 87 Discussion ..................................................................................................................... 89 - Licking and sucking ................................................................................................. 89 - Feeding technique and intake rate ........................................................................... 90 - Feeding habits and intake rate ................................................................................. 92 p. IV - Contents B.6. Liquid food intake in ants: II. Underlying mechanisms ................................ 95 Introduction .................................................................................................................. 96 Materials and Methods ................................................................................................. 97 - Scanning electron microscopy ................................................................................. 97 - Light microscopy ..................................................................................................... 97 - Morphometry ........................................................................................................... 98 Results .......................................................................................................................... 99 - Licking and sucking ................................................................................................ 99 - Glossa surface ........................................................................................................ 101 - Muscle volumes ..................................................................................................... 104 Discussion ................................................................................................................... 109 - Glossa surface ........................................................................................................ 109 - Muscle volumes ..................................................................................................... 111 - How much muscle per unit surface area? .............................................................. 112 Summary ........................................................................................................................... 115 Zusammenfassung ......................................................................................................... 119 References ........................................................................................................................ 123 Appendix ........................................................................................................................... 137 Danksagung ................................................................................................................ 138 Lebenslauf .................................................................................................................. 139 Publications ...............................................................................................................