Parasite–host interactions between Varroa destructor Anderson and Trueman and Apis mellifera L.: Influence of parasitism on flight behaviour and on the loss of infested foragers Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften vorgelegt beim Fachbereich Biologie und Informatik der Johann Wolfgang Goethe-Universität in Frankfurt am Main von Jasna Kralj aus Ljubljana Frankfurt am Main 2004 Parasite–host interactions between Varroa destructor Anderson and Trueman and Apis mellifera L.: Influence of parasitism on flight behaviour and on the loss of infested foragers Parasit-Wirtsbeziehungen zwischen Varroa destructor Anderson and Trueman und Apis mellifera L.: Einfluss der Parasitierung auf das Flugverhalten and auf den Verlust befallener Arbeiterinnen Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften vorgelegt beim Fachbereich Biologie und Informatik der Johann Wolfgang Goethe-Universität in Frankfurt am Main von Jasna Kralj aus Ljubljana Frankfurt am Main 2004 vom Fachbereich Biologie und Informatik der Johann Wolfgang Goethe - Universität als Dissertation angenommen. Dekan: Prof. Dr. H. D. Osiewacz Gutachter: PD Dr. S. Fuchs Prof. Dr. N. Koeniger Datum der Disputation: 27.10.2004 Table of contents Table of contents I List of Tables VI List of Figures VII List of photos IX 1. Literature review 1 1.1. Introduction 1 1.2. Population of parasites in relation to V. destructor 3 1.3. Population of V. destructor 4 1.4. Life history of V. destructor 5 1.5.Factors inside the colony that influence population dynamics of V. destructor 7 1.5.1. Reproduction 7 1.5.1.1. Mite fertility 7 1.5.1.2. Post-capping period 9 1.3.1.3. Brood attraction 10 1.5.2. Behavioural defence facilitating mite mortality 11 1.5.2.1. Grooming behaviour 11 1.5.2.2. Hygienic behaviour 12 1.5.3. Death of mites within colonies 13 1.6. Factors outside the colony that influence population dynamics of V. destructor 15 1.6.1. Spread of mites 15 1.6.1.1.Vertical transmission 16 I 1.6.1.2. Horizontal transmission 16 1.7.2. Death of mites outside colonies 18 2. Objective of the research 20 3. Materials and methods 22 3.1. Infestation of colonies 22 3.2. Marking bees 23 3.3. Measurement of infestation of outflying and returning workers 25 3.3.1.Samplinge device 25 3.3.2. Conducting the experiment 26 3.3.2.1. Sampling procedure 26 3.3.2.2. Determination of infestation of bee samples 27 2.3.2.3. Monitoring mite mortality 27 3.3.3. Statistical procedure 28 3.4. Video recordings of outflying and returning workers 28 3.4.1. Video camera system to record outflying and returning workers 29 3.4.2. Video data collection 31 3.4.3. Statistical procedure 32 3.5. Individual release of workers 32 3.5.1. Registration of returning bees 33 3.5.2. Artificial infestation of marked workers prior to the experiment 35 3.5.3. Conducting the experiment 35 3.5.4. Statistical procedure 38 3.6. Returning of workers in a whole day 38 3.6.1. Statistical procedure 39 II 3.7. Group release of bees 39 3.7.1. Modification of hive entrance to record workers 40 3.7.2. Conducting the experiment 40 3.7.3. Statistical procedure 41 3.8. Orientation toward the nest entrance 41 3.8.1. Design of the experiment 42 3.8.2. Conducting the experiment 42 3.8.3. Statistical procedure 43 3.9. Daily loss of foragers and foragers infestation in colonies by V. destructor 44 3.9.1. Electronic bee counter 44 3.9.2. Sampling outflying and returning bees 45 3.9.3. Statistical procedure 46 3.10. Drifting 47 3.10.1. Observation of drifting in individual workers 47 3.10.2. A choice test for nest recognition 47 3.10.3. Statistical procedure 48 4. Results 49 4.1. Infestation of outflying and returning workers 49 4.2. Video recordings of outflying and returning workers 52 4.2.1. Testing the accuracy of a method 52 4.2.2. Flight duration of workers 53 4.2.3. Infestation of outflying and returning workers 55 4.2.4. Mite loss by non returning of infested foragers 56 4.2.5. Loss of mites from infested foragers 57 4.2.6. Mite gain by uninfested foragers 57 4.2.7.Total mite gain and loss 57 4.3. Individual release of workers 59 4.3.1. Returning time of workers 59 III 4.3.2. Returning of workers in the observation period of 15 min 62 4.3.3. Returning of workers in a whole day 64 4.4. Group release of workers 66 4.5.Orientation toward the nest entrance 68 4.6. Position of V. destructor on workers 71 4.7. Daily loss of foragers in colonies infested by V. destructor 72 4.7.1. Daily loss of foragers in an infested colony over time 72 4.7.2. Simultaneous recording of bee foragers in a colony of high infestation 75 and in a colony of low infestation 4.8.Drifting 78 4.8.1. Observation of drifting in individual workers 78 4.8.2. A choice test for nest recognition 78 5. Discussion 79 5.1. Loss of V. destructor on flight bees: loss of mites 81 5.1.1. Loss of infested foragers 82 5.1.2. Loss of mites from foragers 83 5.1.3. Gain of mites 85 5.1.4. Comparison between Primorsky and Carnica workers 86 5.2. Parasite host interaction-changes in forager behaviour 87 5.2.1. Flight times 87 5.2.1.1. Flight duration 88 5.2.1.2 Returning time 89 5.2.2 Orientation toward the nest entrance 89 5.2.3. Drifting 91 5.2.4. Possible mechanisms by which V. destructor influences flight behaviour 92 IV 5.3. Does loss of mites have an effect on colony infestation? 94 5.4. Loss of mites as a defensive strategy 95 6. Summary 97 7. References 104 8. Appendices 115 Acknowledgements 119 Curriculum vitae 121 Erklärung 122 V List of Tables Table 1. The number of workers, median minimum and maximum flight 55 duration of Carnica (C) and Primorsky workers (P) in the years 2001 and 2002 Table 2. The number of outflying and not returning infested and uninfested workers 57 Table 3. The median returning time of infested (natural and artificial) and 62 uninfested workers used as a control to the artificially and naturally infested workers Table 4. The number and the percentage of returning workers observed during 65 half an hour and later in evening Table 5. The total number of returning workers, the number of mites 67 (infested workers) and the infestation in the time intervals of 5 min according to the location Table 6. The number of infested and uninfested workers which returned directly 71 (nest entrance) or crossed the dummy or empty circle before entering the nest entrance for both years 2001 and 2002 and both position of the dummy (right and left) Table 7. The number of infested and uninfested workers drifting to the same 78 coloured and different coloured hive VI List of Figures Figure 1. The infestation of outflying and returning workers sampled from 5 colonies 50 Figure 2. The infestation of outflying and returning workers sampled in five colonies 51 Figure 3. The ranked difference of infestation between outflying and returning 51 workers in five colonies Figure 4. The number of dead mites per day (daily mite mortality) in week 52 intervals during one month period for five colonies (13.6.-13.9. 2001) Figure 5. The flight duration of outflying and returning workers for the compared 54 127 pairs of infested and uninfested workers of the same age that flew closest in time, recorded in both years 2001 and 2002 Figure 6. The flight duration for the compared pairs of Primorski (n=14) 54 and Carnica (n=41) infested and uninfested workers of the same age that flew closest in time Figure 7. The infestation of outflying and returning Carnica and Primorski workers 56 Figure 8. The percentage of returned and not returned workers that had 58 left the colony either infested either uninfested Figure 9. Returning of mites in Carnica and Primorsky workers 59 Figure 10. The returning time of workers released from different 61 distances in 2002 and 2003 for the compared 130 pairs Figure 11. The returning time according to locations (distance) 62 in the years 2001 and 2002 in the observation period of 15 min Figure 12. The percentage of workers that did not return in the observation period 63 of 15 min in the year 2002 (release from 5m-50m) and 2003 (release from 50m-400m) Figure 13. The total number of infested and uninfested workers that did 65 or not return to the colony until evening Figure 14. The percentage of workers that did not return to the colony for each 66 location (location 1: 20m, location 2: 50m and location 3: 400m) Figure 15. The infestation of returning workers in 5 min intervals and the 67 infestation of workers that did not return back to the colony in the period of 15 min Figure 16. The proportion of workers which did and did not return 68 to the colony in the observation period of 15 min VII