TECHNISCHE UNIVERSITÄT MÜNCHEN Lehrstuhl für Aquatische Systembiologie Host-parasite interactions in aquatic ecosystems – The relationship between fishes and endangered freshwater mussels Jens-Eike Täubert Vollständiger Abdruck der von der Fakultät Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. M. W. Pfaffl Prüfer der Dissertation: 1. Univ.-Prof. Dr. J. P. Geist 2. apl. Prof. Dr. R. P. Kühn Die Dissertation wurde am 23.04.2014 bei der Technischen Universität München eingereicht und durch die Fakultät Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt am 27.06.2014 angenommen. Host-parasite interactions in aquatic ecosystems – The relationship between fishes and endangered freshwater mussels Brown trout (Salmo trutta L.) with encysted larvae of the freshwater pearl mussel (Margaritifera margaritifera L.). Content I Table of Contents List of Figures ........................................................................................................................ V List of Tables ........................................................................................................................ VI Preface ................................................................................................................................ VII Summary ............................................................................................................................ VIII Zusammenfassung ................................................................................................................ X 1. General introduction .......................................................................................................... 1 1. 1. The importance of freshwater mussels in aquatic ecosystems ................................... 1 1. 2. Life cycle of unionoid mussels .................................................................................... 1 1. 3. Larval types of freshwater mussels in relation to phylogeny and distribution .............. 3 1. 4. Study species of this work - Unio crassus and Margaritifera margaritifera, two endangered central European unionoid species ......................................................... 5 1. 4. 1. Unio crassus (Phillipsson, 1788) ......................................................................... 5 1. 4. 2. Margaritifera margaritifera (Linnaeus, 1758) ....................................................... 7 1. 5. Objectives .................................................................................................................. 9 2. Host-specificity of the endangered thick-shelled river mussel (Unio crassus, Philipsson 1788) and implications for conservation ..........................................................11 2. 1. Abstract.....................................................................................................................11 2. 2. Introduction ...............................................................................................................12 2. 3. Methods ....................................................................................................................13 2. 3. 1. Collection of glochidia ........................................................................................13 2. 3. 2. Infestation procedure .........................................................................................14 2. 3. 3. Host fish suitability assessment .........................................................................15 2. 3. 4. Statistical analyses ............................................................................................15 2. 4. Results ......................................................................................................................16 2. 5. Discussion ................................................................................................................22 2. 6. Conclusions and implications for conservation ..........................................................26 3. The relationship between endangered thick-shelled river mussel (Unio crassus) and its host fishes ....................................................................................................................28 Content II 3. 1. Abstract.....................................................................................................................28 3. 2. Introduction ...............................................................................................................28 3. 3. Methods ....................................................................................................................30 3. 3. 1. Collection of glochidia for artificial infestation .....................................................30 3. 3. 2. Artificial infestation procedure and maintenance of fishes ..................................30 3. 3. 3. Assessment of infestation rates and metamorphosed mussels ..........................32 3. 3. 4. Natural infestation and fish species composition in the wild ...............................32 3. 3. 5. Statistical analyses ............................................................................................33 3. 4. Results ......................................................................................................................34 3. 4. 1. Artificial infestations - infestation and excystment rates .....................................34 3. 4. 2. Timing of excystment .........................................................................................38 3. 4. 3. Glochidia sizes ..................................................................................................38 3. 4. 4. Fish species composition in U. crassus streams ................................................39 3. 4. 5. Natural infestations - infestation and excystment rates ......................................41 3. 5. Discussion ................................................................................................................42 3. 5. 1. Differences in assessing host suitability in the laboratory and in the wild ...........43 3. 5. 2. Artificial infestations - infestation and excystment rates .....................................43 3. 5. 3. Timing of excystment .........................................................................................45 3. 5. 4. Glochidia sizes ..................................................................................................45 3. 5. 5. Fish species composition of U. crassus streams ................................................45 3. 5. 6. Natural infestation - infestation and excystment rates ........................................47 3. 6. Conclusions ..............................................................................................................47 4. Suitability of different salmonid strains as hosts for the endangered freshwater pearl mussel (Margaritifera margaritifera L.) ..............................................................................49 4. 1. Abstract.....................................................................................................................49 4. 2. Introduction ...............................................................................................................50 4. 3. Methods ....................................................................................................................51 4. 4. Results ......................................................................................................................54 4. 4. 1. Infection procedure in calcareous water ............................................................54 4. 4. 2. Susceptibility of different host fish species and strains .......................................54 Content III 4. 4. 3. Glochidia size on different host species and strains ...........................................58 4. 5. Discussion ................................................................................................................59 4. 5. 1. Infection procedure in calcareous water ............................................................59 4. 5. 2. Susceptibility of different host fish species and strains .......................................60 4. 5. 3. Glochidia size on different host species and strains ...........................................62 5. Variable development and excystment of freshwater pearl mussel (Margaritifera margaritifera L.) at constant temperature ..........................................................................63 5. 1. Abstract:....................................................................................................................63 5. 2. Introduction ...............................................................................................................63 5. 3. Methods ....................................................................................................................64 5. 4. Results ......................................................................................................................66 5. 5. Discussion ................................................................................................................67 6. Critical swimming speed of brown trout (Salmo trutta) infested with freshwater pearl mussel (Margaritifera margaritifera) glochidia and implications