Feeding ecology of the semi-terrestrial crab Ucides cordatus cordatus (Decapoda: Brachyura) in a mangrove forest in northern Brazil Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) vorgelegt von Inga Nordhaus angefertigt am Zentrum für Marine Tropenökologie (ZMT) innerhalb des Fachbereichs 2 der Universität Bremen Bremen 2003 Principal supervisor: Prof. Dr. Matthias Wolff, ZMT at the University of Bremen Co-supervisor: Prof. Dr. Wolf Arntz, Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven; University of Bremen I CONTENTS ABBREVIATION LIST………………………………………………………………………………..III SUMMARY……………………………………………………………………………………...……. V RESUMO……………………………………………………………………………………………..VII ZUSAMMENFASSUNG……………………………………………………………………………...X 1 GENERAL INTRODUCTION ........................................................................................... 1 2 STUDY AREA.................................................................................................................. 6 3 DIET AND CONSUMPTION .......................................................................................... 13 3.1 Introduction .............................................................................................................13 3.2 Material and methods .............................................................................................16 3.2.1 Stomach content analyses................................................................................. 16 3.2.2 Food preferences............................................................................................... 17 3.2.3 Food availability ................................................................................................. 19 3.2.3.1 Litter material in burrows and litter standing stock ..................................... 19 3.2.3.2 Litter fall...................................................................................................... 19 3.2.4 Evacuation ......................................................................................................... 21 3.2.5 Daily food intake ................................................................................................ 22 3.2.6 Statistical analyses ............................................................................................ 23 3.3 Results....................................................................................................................24 3.3.1 Stomach content analyses................................................................................. 24 3.3.2 Food preferences............................................................................................... 26 3.3.3 Food availability ................................................................................................. 29 3.3.3.1 Litter material in burrows and litter standing stock ..................................... 29 3.3.3.2 Litter fall...................................................................................................... 31 3.3.4 Evacuation ......................................................................................................... 33 3.3.5 Daily food intake ................................................................................................ 35 3.4 Discussion ..............................................................................................................39 3.4.1 Stomach content analyses................................................................................. 39 3.4.2 Food preferences............................................................................................... 40 3.4.3 Food availability ................................................................................................. 46 3.4.4 Evacuation ......................................................................................................... 49 3.4.5 Daily food intake ................................................................................................ 50 4 FEEDING PERIODICITY AND BEHAVIOUR ................................................................ 59 4.1 Introduction .............................................................................................................59 4.2 Material and methods .............................................................................................61 4.2.1 Analysis of gastrointestinal contents.................................................................. 61 4.2.2 Binocular observation ........................................................................................ 62 4.2.3 Camera observation........................................................................................... 63 4.3 Results....................................................................................................................64 4.3.1 Analysis of gastrointestinal contents.................................................................. 64 4.3.2 Binocular observation ........................................................................................ 64 4.3.3 Camera observation........................................................................................... 67 4.4 Discussion ..............................................................................................................75 II 5 ASSIMILATION AND MICROBIOLOGICAL INVESTIGATIONS ................................... 83 5.1 Introduction .............................................................................................................83 5.2 Material and methods .............................................................................................86 5.2.1 Assimilation........................................................................................................ 89 5.2.1.1 Sampling .................................................................................................... 89 5.2.1.2 Sample processing..................................................................................... 91 5.2.2 Microbiological investigations............................................................................. 93 5.2.2.1 Sampling .................................................................................................... 93 5.2.2.2 Sample processing..................................................................................... 96 5.3 Results....................................................................................................................99 5.3.1 Assimilation........................................................................................................ 99 5.3.1.1 Food characteristics ................................................................................... 99 5.3.1.2 Assimilation efficiency .............................................................................. 109 5.3.2 Microbiological investigations........................................................................... 111 5.3.2.1 Microbial abundance ................................................................................ 111 5.3.2.2 Microbial community structure ................................................................. 114 5.3.2.3 Bacterial biomass..................................................................................... 116 5.4 Discussion ............................................................................................................118 5.4.1 Assimilation...................................................................................................... 118 5.4.1.1 Food characteristics ................................................................................. 118 5.4.1.2 Assimilation efficiency .............................................................................. 122 5.4.1.3 Energy and nutrient budget...................................................................... 123 5.4.2 Microbiological investigations........................................................................... 128 5.4.2.1 Microbial abundance and community structure........................................ 128 5.4.2.2 The role of microorganisms for the nutrition of U. cordatus ..................... 131 6 CONCLUSIONS AND PERSPECTIVES ..................................................................... 137 7 ACKNOWLEDGEMENTS............................................................................................ 143 8 REFERENCES ............................................................................................................ 145 9 LIST OF FIGURES ...................................................................................................... 157 10 LIST OF TABLES ........................................................................................................ 159 11 APPENDICES.............................................................................................................. 164 11.1 Appendix I: Diet and consumption – Statistical analysis.......................................164 11.2 Appendix II: Feeding periodicity and behaviour – Statistical analysis...................172 11.3 Appendix III: Assimilation and microbiological investigations-Statistical analysis.176 III Abbreviation list SI untits are not included Av Avicennia germinans AF Avicennia forest BDW body dry weight CL carapace length CW carapace width DW dry weight f female FC Furo do Chato FG Furo Grande GIC gastrointestinal contents La Laguncularia racemosa Lab Laboratory m male MF mixed forest Rh Rhizophora