Daphnia carapace: form, function, structure and plasticity Dissertation to obtain the degree Doctor Rerum Naturalium (Dr. rer. nat.) at the Faculty of Biology and Biotechnology Ruhr University Bochum International Graduate School of Biosciences Ruhr University Bochum Department of Animal Ecology, Evolution & Biodiversity Submitted by Sebastian Kruppert From Frankfurt am Main, Germany Bochum, October 2016 First Supervisor: Prof. Dr. R. Tollrian Second Supervisor: Prof. Dr. D. Begerow Daphnia Carapax: Form, Funktion, Struktur und Plastizität Dissertation Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschaften der Fakultät für Biologie und Biotechnologie der Ruhr-Universität Bochum Internationale Graduiertenschule Biowissenschaften Ruhr-Universität Bochum Angefertigt am Lehrstuhl für Evolutionsökologie und Biodiversität der Tiere vorgelegt von Sebastian Kruppert aus Frankfurt am Main Bochum, Oktober 2016 Referent: Prof. Dr. R. Tollrian Korreferent: Prof. Dr. D. Begerow „In den kleinsten Dingen zeigt die Natur die allergrößten Wunder“ Carl von Linné Für meine Familie Table of contents Table of contents Introduction ......................................................................................................................8 Predators and prey ....................................................................................................9 Permanent defenses ................................................................................................. 10 Inducible defenses................................................................................................... 13 Inducible defenses in Daphnia ................................................................................ 17 Functionality of inducible morphological defenses .................................................. 20 Objectives ............................................................................................................... 21 1. Carapace structure ........................................................................................... 22 2. Structure and shape contribution to carapace resistance ............................... 23 Biomechanical methods within an ecological framework ........................................ 23 3. The catching basket of Chaoborus .................................................................... 25 Materials and Methods ................................................................................................ 27 1. Carapace structure ........................................................................................... 28 Experimental organisms .......................................................................................... 28 In vivo light microscopy .......................................................................................... 28 Whole mounts stained with hematoxylin and eosin ................................................. 28 Scanning electron microscopy ................................................................................. 29 Thin sections ........................................................................................................... 30 Ultra-thin sections and scanning transmission electron microscopy ......................... 30 Hemolymphatic gauge pressure............................................................................... 31 2. Structure and shape contribution to carapace resistance ............................... 33 Experimental organisms .......................................................................................... 33 Induction of morphological defenses in D. pulex and D. longicephala..................... 33 Microscopy, modelling and simulation .................................................................... 34 Daphnia carapace: form, function, structure and plasticity 5 Table of contents Procuticle analysis .................................................................................................. 34 Procuticle Young´s modulus ................................................................................... 35 Carapace structure and finite element analysis ........................................................ 38 Optical imaging of carapace shape .......................................................................... 41 Carapace shape modelling and finite element analysis............................................. 46 Structural Young’s-modulus and critical force ........................................................ 48 3. The catching basket of Chaoborus .................................................................... 50 Experimental Organisms and induction of the daphniids defenses ........................... 50 High speed recordings ............................................................................................. 51 microCT imaging and 3D reconstruction ................................................................. 51 Surface mesh and animation.................................................................................... 52 Feeding Experiments .............................................................................................. 53 Bite force estimation ............................................................................................... 53 Results ............................................................................................................................... 56 1. Carapace structure ........................................................................................... 57 Morphology of the carapace and distribution of the pillars ...................................... 57 Ultrastructure of the pillars ..................................................................................... 64 Hemolymphatic pressure ......................................................................................... 64 2. Structure and shape contribution to carapace resistance ............................... 66 Structure ................................................................................................................. 66 Shape ...................................................................................................................... 71 3. The catching basket of Chaoborus .................................................................... 76 The catching process ............................................................................................... 76 Morphology of the catching basket ......................................................................... 78 The catching basket ................................................................................................ 80 The Antennae.......................................................................................................... 80 The labral setae and prelabral appendage ................................................................ 81 The mandibles ........................................................................................................ 81 The mandible muscles ............................................................................................. 82 The Mandible joint.................................................................................................. 82 Daphnia carapace: form, function, structure and plasticity 6 Table of contents The mandibular fan ................................................................................................. 82 The rhinopharynx.................................................................................................... 83 Animation of the catching event .............................................................................. 83 Efficiency of the catching basket ............................................................................. 85 Bite force estimation ............................................................................................... 87 Discussion ......................................................................................................................... 89 1. Carapace structure ........................................................................................... 90 Carapace proximal and distal integument structure .................................................. 90 Interconnecting pillars............................................................................................. 92 Pillar function ......................................................................................................... 93 2. Structure and shape contribution to carapace resistance ............................... 96 Structure ................................................................................................................. 96 Shape ...................................................................................................................... 97 Conclusion .............................................................................................................. 99 3. The catching basket of Chaoborus .................................................................. 100 Concluding Discussion .............................................................................................. 104 Outlook ................................................................................................................. 105 References ...................................................................................................................... 106 Summary .......................................................................................................................