This work is focused on the study of physiology and proteome of the the mite Varroa destructor and on comparison with the honeybee Apis mellifera. Varroa is currently a major problem for beekeeping, because infects most of the colonies. The control of the mite can not be done without residues both in the hive and for example in the honey or other resources used by the man. Another problem can also be the simultaneously discussed issue of the connection with the Colony Collapse Disorder. The internal anatomy of V. destructor was studied by using paraffin histology. On histological sections stained using hematoxylin and PAS was possible to observe the mite digestive system, but also egg, ovaries or brain. The primary aim of this study was to identify the proteins of mite V. destructor and bee A. mellifera as a host of this parasite. For the electrophoretic separation was used two- dimensional gel electrophoresis, where the second dimension was carried out using 12% and 15% SDS-PAGE. The most abundant spots were selected for analysis using MALDI TOF/TOF mass spectrometry. The most abundant protein identified in samples of V. destructor was hexamerin, arginine kinase or hemelipoglycoprotein precursor. Hexamerins were also identified as the major proteins in the pupae samples. On the contrary the main...

Submitted by Ana Damasceno (ana.damasceno@unipampa.edu.br) on 2016-10-13T18:21:12Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Identificacao de virus que afetam apis mellifera.pdf: 2079239 bytes, checksum: 490f111cf7ddb616e9d3cc3373a5be07 (MD5) / Made available in DSpace on 2016-10-13T18:21:12Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Identificacao de virus que afetam apis mellifera.pdf: 2079239 bytes, checksum: 490f111cf7ddb616e9d3cc3373a5be07 (MD5) Previous issue date: 2014-04-30 / A apicultura é uma atividade de importância econômica e ambiental. O clima e a flora do Brasil somados à presença da abelha africanizada conferem um excelente potencial apícola. Entretanto, as abelhas são suscetíveis a uma variedade de doenças. Vários são os patógenos que podem acometer abelhas melíferas, sendo o foco deste trabalho a relação entre o ácaro Varroa destructor e os vírus que acometem abelhas. V. destructor é um ectoparasita, sendo a varroose, doença causada por este ácaro, responsável pela mortalidade de milhares de colônias de Apis mellifera em várias partes do mundo. Entretanto, os danos causados pela varroose variam com a raça de abelhas e condições climáticas. Embora o ácaro cause poucos danos nas colônias de abelhas africanizadas no Brasil, a coexistência deste ectoparasita com determinados tipos virais pode comprometer seriamente a saúde da colônia, uma vez que muitos destes vírus tem sua transmissão relacionada ao ectoparasita, apontando este como um vetor da infecção. Portanto, faz-se necessária a identificação de quais vírus estão associados ao ácaro e que, possivelmente, utilizam-se do ácaro como vetor. Dentro deste contexto, objetivamos verificar a existência de vírus associados ao ácaro V. destructor em espécimes coletadas em apiários de diferentes regiões do Rio Grande do Sul. Foram realizadas coletas de ácaros em apiários localizados em oito municípios gaúchos. A partir das amostras coletadas, foi realizada extração de RNA total e síntese de cDNA. O cDNA sintetizado foi submetido à PCR utilizando-se 9 pares de primers para detecção de vírus que afetam abelhas e um par de primers para controle endógeno. As amostras foram submetidas a eletroforese em gel de agarose. Identificou-se, em três apiários, a presença dos vírus SBV (Vírus da Cria Ensacada) e VDV-1 (Vírus Varroa destructor-1) associados ao ácaro V. destructor. Estes dados são inéditos uma vez que estudos semelhantes nunca foram realizados no Brasil ou em abelhas africanizadas e poderão servir de base no desenvolvimento de programas de controle deste parasita. / Beekeeping is an activity that has both economic and environmental importance. Brazil has excellent climate and flora for beekeeping, and alongside the presence of Africanized bee populations, it has great potential for apiculture. However, Apis mellifera bees are susceptible to a variety of diseases. There are several pathogens that can affect honeybees and the focus of this work is to assess the relationship between the Varroa destructor mite and viruses that affect bees in the state of Rio Grande do Sul. V. destructor is an ectoparasite and the disease caused by this mite may be responsible for the death of thousands of colonies of A. mellifera in several parts of the world. However, the damage caused by the varroa mite vary according to the race of the affected bees and weather conditions. Although the varroa mite cause little damage in colonies of Africanized bees in Brazil, the coexistence of this ectoparasite with certain types of viruses can seriously compromise the health of the colony, since many of these viruses use the mite for transmission, pointing this as a probable vector. Therefore, it is necessary to identify which viruses are associated with the mite and that possibly use it as vector. Within this context, the objective of this work is to verify the presence of viruses associated with the V. destructor mite in specimens collected in apiaries in different regions of Rio Grande do Sul. Mite collections were made in apiaries located in eight different cities in the state. Collected samples were subjected to total RNA extrection and cDNA synthesis was performed. The synthesized cDNA was subjected to PCR using nine primer pairs for detection of viruses affecting bee and one pair of primers for endogenous control. Amplified samples were subjected to electrophoresis on agarose gel. With this work, we have been able to identify in the presence of SBV and VDV-1 virus associated with V. destructor mite in three different apiaries. The obtained data are novel, since similar studies have never been conducted before in Brazil or using Africanized bee colonies, and could be used as basis in development of control strategies of this parasite.

The European honeybee (Apis mellifera) is a managed insect pollinator of global economic importance. Over the last few decades honeybees have been undergoing a major health crisis, with one of the biggest causes the parasitic mite, Varroa destructor and its role in changing the viral landscape of deformed wing virus (DWV), which consists of two major variants: DWV-A and DWV-B. Prior to the start of this project there was limited information known about the mechanisms behind the relationships between Varroa, DWV and honeybees. The overarching aim of this project was to further enhance our understanding of these complex relationships, focusing on the impact of Varroa DWV transmission and differences between the main DWV variants. One of the initial obstacles to understanding these complex interactions was the inability to accurately quantify DWV variants. Prior to the start of this project, there was a need for an accurate assay for the quantification of DWV-A, DWV-B and total DWV, allowing the role of both variants in viral transmission and establishment to be investigated. While primers did exist for DWV quantification, the majority did not distinguish between variants, or provide accurate levels of DWV. Given these challenges in variant detection, a new assay for the quantification of DWV-A, DWV-B and total DWV was designed and validated. The assay consists of an external plasmid standard with distinct sections, for the detection of variants and total DWV. This DWV variant plasmid assay was essential for further transmission studies in this project. DWV variant transmission was explored using a variety of different methods. A new in vitro feeding system was used, to allow investigations into Varroa DWV variant transmission in isolation. The feeding system utilises locust haemolymph, allowing changes in DWV transmission to be detected. In multiple feeding experiments significant changes in DWV transmission were detected. Significant changes in DWV composition within feeding Varroa were detected with decreased levels of DWV, and changing variant levels. Switches in variant composition within mites and transmission rates occurred during Varroa in vitro feeding. These variant switches occurred in both directions from DWV-A to DWV-B, and DWV-B to DWV-A dominance. These changes in mite variant composition corresponded to changes in levels of replicating strands. iv These changes in DWV transmission, composition and replicating strand detection were only seen due to the use of this in vitro feeding system. The in vitro work provided valuable information about Varroa variant transmission and composition changes during feeding but this is not a natural system. Honeybee pupae from a Varroa-free area with extremely low DWV titres provided the opportunity to investigate Varroa variant transmission and pupal DWV establishment. Over 96 hours total DWV levels underwent a 1339408X fold increase, within pupae following Varroa feeding, with a sharp increase after 12 hours, followed by a plateau after 60 hours. Within this time period, DWV-A underwent a similar increase, while DWV-B increased at a much slower rate (33X fold change). In contrast to the in vitro work, mite DWV levels did not decrease during feeding. The impact of natural Varroa cell infestation on L5 larvae was investigated, showing no significant effects between pupal total DWV levels and mite density, and DWV levels between infested and none-infested larvae. However, this lack of significance could be attributed to the use of L5 larvae, which had only undergone a maximum of 24 hours Varroa feeding within the cell. Additionally, the use of two drug treatments (ribavirin and hydroxyurea) to reduce DWV levels was explored. Both drug treatments were tested against Varroa and honeybees, using a variety of methods: immersion (Varroa), injections (honeybees) and feeding (both). While neither drug treatment resulted in consistent DWV decreases, some reduction in DWV levels were seen following Varroa soaking in drug solutions. A significant decrease in DWV was seen in honeybees following bolus and ad libitum feeding of drug treatments. Overall, information and insights have been gained regarding the complex relationship between Varroa, honeybees and DWV. A new DWV variant qPCR assay was developed and utilised in subsequent studies. DWV variant switches in both transmission rates and mite composition were found to occur in in vitro studies. Differences in DWV variant establishment within honeybees were detected following Varroa in vivo feeding, in low DWV pupae. Though the tested drug treatments did not affect DWV levels, this highlights the difficultly facing the establishment of any DWV treatment.

Submitted by Sandro Camargo (sandro.camargo@unipampa.edu.br) on 2015-05-07T22:33:38Z No. of bitstreams: 1 126110036.pdf: 2091532 bytes, checksum: 8020f2b19bedcc2aebd080e502846a88 (MD5) / Made available in DSpace on 2015-05-07T22:33:38Z (GMT). No. of bitstreams: 1 126110036.pdf: 2091532 bytes, checksum: 8020f2b19bedcc2aebd080e502846a88 (MD5) Previous issue date: 2014-04-30 / A apicultura é uma atividade de importância econômica e ambiental. O clima e a flora do Brasil somados à presença da abelha africanizada conferem um excelente potencial apícola. Entretanto, as abelhas são suscetíveis a uma variedade de doenças. Vários são os patógenos que podem acometer abelhas melíferas, sendo o foco deste trabalho a relação entre o ácaro Varroa destructor e os vírus que acometem abelhas. V. destructor é um ectoparasita, sendo a varroose, doença causada por este ácaro, responsável pela mortalidade de milhares de colônias de Apis mellifera em várias partes do mundo. Entretanto, os danos causados pela varroose variam com a raça de abelhas e condições climáticas. Embora o ácaro cause poucos danos nas colônias de abelhas africanizadas no Brasil, a coexistência deste ectoparasita com determinados tipos virais pode comprometer seriamente a saúde da colônia, uma vez que muitos destes vírus tem sua transmissão relacionada ao ectoparasita, apontando este como um vetor da infecção. Portanto, faz-se necessária a identificação de quais vírus estão associados ao ácaro e que, possivelmente, utilizam-se do ácaro como vetor. Dentro deste contexto, objetivamos verificar a existência de vírus associados ao ácaro V. destructor em espécimes coletadas em apiários de diferentes regiões do Rio Grande do Sul. Foram realizadas coletas de ácaros em apiários localizados em oito municípios gaúchos. A partir das amostras coletadas, foi realizada extração de RNA total e síntese de cDNA. O cDNA sintetizado foi submetido à PCR utilizando-se 9 pares de primers para detecção de vírus que afetam abelhas e um par de primers para controle endógeno. As amostrasforam submetidas a eletroforese em gel de agarose. Identificou-se, em três apiários, a presença dos vírus SBV (Vírus da Cria Ensacada) e VDV-1 (Vírus Varroa destructor-1) associados ao ácaro V. destructor. Estes dados são inéditos uma vez que estudos semelhantes nunca foram realizados no Brasil ou em abelhas africanizadas e poderão servir de base no desenvolvimento de programas de controle deste parasita. / Beekeeping is an activity that has both economic and environmental importance. Brazil has excellent climate and flora for beekeeping, and alongside the presence of Africanized bee populations, it has great potential for apiculture. However, Apis mellifera bees are susceptible to a variety of diseases. There are several pathogens that can affect honeybees and the focus of this work is to assess the relationship between the Varroa destructor mite and viruses that affect bees in the state of Rio Grande do Sul. V. destructor is an ectoparasite and the disease caused by this mite may be responsible for the death of thousands of colonies of A. mellifera in several parts of the world. However, the damage caused by the varroa mite vary according to the race of the affected bees and weather conditions. Although the varroa mite cause little damage in colonies of Africanized bees in Brazil, the coexistence of this ectoparasite with certain types of viruses can seriously compromise the health of the colony, since many of these viruses use the mite for transmission, pointing this as a probable vector. Therefore, it is necessary to identify which viruses are associated with the mite and that possibly use it as vector. Within this context, the objective of this work is to verify the presence of viruses associated with the V. destructor mite in specimens collected in apiaries in different regions of Rio Grande do Sul. Mite collections were made in apiaries located in eight different cities in the state. Collected samples were subjected to total RNA extrection and cDNA synthesis was performed. The synthesized cDNA was subjected to PCR using nine primer pairs fordetection of viruses affecting bee and one pair of primers for endogenous control. Amplified samples were subjected to electrophoresis on agarose gel. With this work, we have been able to identify in the presence of SBV and VDV-1 virus associated with V. destructor mite in three different apiaries. The obtained data are novel, since similar studies have never been conducted before in Brazil or using Africanized bee colonies, and could be used as basis in development of control strategies of this parasite.

Submitted by Ana Damasceno (ana.damasceno@unipampa.edu.br) on 2016-11-30T18:54:51Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Identificação de vírus que afetam apis mellifera associados ao ácaro ectoparasita varroa destructor em apiários do Rio Grande do Sul.pdf: 2079239 bytes, checksum: 490f111cf7ddb616e9d3cc3373a5be07 (MD5) / Made available in DSpace on 2016-11-30T18:54:51Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Identificação de vírus que afetam apis mellifera associados ao ácaro ectoparasita varroa destructor em apiários do Rio Grande do Sul.pdf: 2079239 bytes, checksum: 490f111cf7ddb616e9d3cc3373a5be07 (MD5) Previous issue date: 2014-04-30 / A apicultura é uma atividade de importância econômica e ambiental. O clima e a flora do Brasil somados à presença da abelha africanizada conferem um excelente potencial apícola. Entretanto, as abelhas são suscetíveis a uma variedade de doenças. Vários são os patógenos que podem acometer abelhas melíferas, sendo o foco deste trabalho a relação entre o ácaro Varroa destructor e os vírus que acometem abelhas. V. destructor é um ectoparasita, sendo a varroose, doença causada por este ácaro, responsável pela mortalidade de milhares de colônias de Apis mellifera em várias partes do mundo. Entretanto, os danos causados pela varroose variam com a raça de abelhas e condições climáticas. Embora o ácaro cause poucos danos nas colônias de abelhas africanizadas no Brasil, a coexistência deste ectoparasita com determinados tipos virais pode comprometer seriamente a saúde da colônia, uma vez que muitos destes vírus tem sua transmissão relacionada ao ectoparasita, apontando este como um vetor da infecção. Portanto, faz-se necessária a identificação de quais vírus estão associados ao ácaro e que, possivelmente, utilizam-se do ácaro como vetor. Dentro deste contexto, objetivamos verificar a existência de vírus associados ao ácaro V. destructor em espécimes coletadas em apiários de diferentes regiões do Rio Grande do Sul. Foram realizadas coletas de ácaros em apiários localizados em oito municípios gaúchos. A partir das amostras coletadas, foi realizada extração de RNA total e síntese de cDNA. O cDNA sintetizado foi submetido à PCR utilizando-se 9 pares de primers para detecção de vírus que afetam abelhas e um par de primers para controle endógeno. As amostras foram submetidas a eletroforese em gel de agarose. Identificou-se, em três apiários, a presença dos vírus SBV (Vírus da Cria Ensacada) e VDV-1 (Vírus Varroa destructor-1) associados ao ácaro V. destructor. Estes dados são inéditos uma vez que estudos semelhantes nunca foram realizados no Brasil ou em abelhas africanizadas e poderão servir de base no desenvolvimento de programas de controle deste parasita.

Zugl.: Hohenheim, Univ., Diss., 2006

University, Diss., 2004--Frankfurt (Main). / Zsfassung in engl. und dt. Sprache.

The honey bee is one of the most familiar insects in the world, and plays an important role in the global economy providing essential pollination services to crops, fruit trees and vegetables. However, honey bee health is severely threatened by the ectoparasitic mite Varroa destructor, which feeds on the hemolymph of pupal and adult bees, resulting in loss of nutrients and circulatory fluids, decreased overall body weight and eventually the death of the bees. To investigate the molecular defense mechanisms of the honey bee against varroa mite infestation, we employed DNA microarray analysis to compare gene expression of two contrasting honey bee colony phenotypes selected from the Saskatraz breeding program. One designated as G4 is susceptible to the varroa mite, while the other designated as S88 is highly tolerant to the varroa. Total RNAs were isolated from bees at two different stages, dark-eyed pupa and adult worker, infected or non-infected with varroa mites, and used for DNA microarray analysis. The results showed that distinct sets of genes were differentially regulated in the varroa-tolerant and varroa-susceptible honey bee phenotypes, with and without varroa infestation. In both phenotypes, there were more differentially-expressed genes identified at the pupal stage than at the adult stage, indicating that at the pupal stage honey bees are more responsive to the varroa infestation than adult bees. In the phenotype comparisons, substantially more differentially-expressed genes were found in the tolerant than susceptible line, indicating that the tolerant phenotype has an increased capacity to mobilize the expression of the genes in response to varroa mite infestation. Based on function, the differentially-expressed genes could be classified into groups that are involved in olfactory signal transduction, detoxification, metabolism and exoskeleton formation, implying several possible mechanisms for the host-parasite interaction and resistance. Quantitative RT-PCR was used to confirm the data obtained from the DNA microarray hybridization. Eleven out of twelve genes selected based on the microarray data showed consistent expression patterns measured by both methods. Overall, comprehensive evaluation of the gene expression of honey bees in response to the mite infestation by DNA microarray has revealed several possible molecular mechanisms for the host defense against the pest. Identification of highly differentially expressed genes between the two phenotypes provides potential biomarkers that can be used for breeding honey bees resistant to the varroa mite.

The European honey bee, Apis mellifera, is an important pollinator of horticultural and agricultural field crops, providing ≈ 90% of all commercial pollination services (Genersch et al. 2010). The recent rise in colony loss due to Colony Collapse Disorder (CCD) has been a source of concern for both beekeepers and the apiculture industry. One of the factors implicated in CCD is infestation by the ectoparasitic mite, Varroa destructor. Initial efforts to control the mite relied heavily on regular application of miticides without regard to actual mite infestation levels. This approach has led to problems of resistance in the mite and contamination of the hive and hive-products. Because it is unlikely that miticides will be removed as an option for mite management, a precision mite management (PMM) approach using information on the spatiotemporal distribution of the mite to improve sampling and treatments is seen as a viable option, particularly with respect to treatment costs and impacts on the environment. The primary objective of this study was to develop an understanding of the spatiotemporal distribution of the Varroa mite and bee brood within hives for the purpose of developing a PMM approach for the mite. Varroa mite populations were sampled from May to June, 2012 and February to October, 2013. Sampling was conducted with three commonly used sampling methods: soapy water roll (SWR), brood uncapping, and a modified sticky board; brood uncapping, however, was discontinued during the study due to hive the labor cost and harmful effects of this method to the hives. Similar trends in mite population levels were observed using the soapy water roll and sticky board sampling methods. Spearman's nonparametric analysis showed that there was a significant correlation (ρ = 0.47, P<0.001) in mite population levels for the soapy water roll and sticky board methods for sampling conducted from February to September, 2013 (the SWR method was not used in October). This was despite the fact that there was no significant correlation (ρ= -0.03, P = 0.8548) between the two sampling methods during the spring sampling period from February to April, 2013. The observed lack of correlation between the two sampling methods in early spring was likely due to the low population of brood in the hive, which caused the majority of the mites to remain on adult bees. Mites per 100 adult bees, therefore, appear to reflect mite population levels within the hive more closely than mite fall on sticky borad during the February to April sampling period. This suggests that the soapy water roll method is a better method for estimating mite population levels within the hive in the early spring compared with the sticky board method. Geospatial analyses of the distributions of mite fall on the sticky boards were conducted using geostatistics and Spatial Analysis by Distance IndicEs (SADIE). Both analyses showed that mite fall on the sticky board was generally aggregated and the aggregation increased with mite population levels. The average range of the variogram from geostatistical analysis was estimated at 4 sticky board cells; this range value was increased to 5 cells and was used to develop a systematic outside-range sampling protocol for mites on a sticky board. The results showed that the accuracy of the systematic outside-range sampling compared well with that of the traditional sticky board counting method in estimating total mite fall, but required only 60% of the effort (i.e., counting 63 instead of 105 cells). SADIE analysis showed that there is an overall association between the distribution of mite fall on a sticky board and the distribution of brood within a hive. A greater degree of correspondence was also observed in the association of drone and mite distributions during May to June; greater correspondence in worker brood and mite associations was observed in August and September. These differences may be due to relative amounts of the two types of brood present within the hive. A test of the efficacy of precision application of Varroa mite treatment based on the association between drone brood and mite fall resulted in a significantly greater reduction in mite levels on the sticky board using a traditional miticide treatment method compared with the control and precision treatments (𝜒2 =362.571; df = 2; P <0.0001); mite population levels with the precision method, however, were significantly reduced compared with the control. / Master of Science in Life Sciences

The Western Honeybee (Apis mellifera) is among the most versatile species in the world. Its adaptability is rooted in thousands of the differently specialized individuals acting jointly together. Thus, bees that are able to handle a certain task or condition well can back up other individuals less capable to do so on the colony level. Vice versa, the latter individuals might perform better in other situations. This evolutionary recipe for success ensures the survival of colonies despite challenging habitat conditions. In this context, the ectoparasitic mite Varroa destructor reflects the most pronounced biotic challenge to honeybees worldwide. Without proper treatment, infested colonies rapidly dwindle and ultimately die. Nevertheless, resistance behaviours against this parasite have evolved in some populations through natural selection, enabling colonies to survive untreated. In this, different behaviours appear to be adapted to the respective habitat conditions and may complement each other. Yet, the why and how of this behavioural response to the mite remains largely unknown. My thesis focuses on the biological background of Varroa-resistance traits in honeybees and presents important findings for the comprehension of this complex host-parasite interaction. Based on this, I draw implications for both, applied bee breeding and scientific investigations in the field of Varroa-resistance. Specifically, I focus on two traits commonly found in resistant and, to a lower degree, also mite-susceptible colonies: decreased mite reproduction and the uncapping and subsequent recapping of sealed brood cells. Examining failures in the reproductive success of mites as a primary mechanism of Varroa-resistance, I was able to link them to specific bee behaviours and external factors. Since mite reproduction and the brood rearing of bees are inevitably connected, I first investigated the effects of brood interruption on the reproductive success of mites. Brood interruption decreased the reproductive success of mites both immediately and in the long term. By examining the causes of reproductive failure, I could show that this was mainly due to an increased share of infertile mites. Furthermore, I proved that interruption in brood rearing significantly increased the expression of recapping behaviour. These findings consequently showed a dynamic modulation of mite reproduction and recapping, as well as a direct effect of brood interruption on both traits. To further elucidate the plasticity in the expression of both traits, I studied mite reproduction, recapping behaviour and infestation levels over the course of three years. The resulting extensive dataset unveiled a significant seasonal variation in mite reproduction and recapping. In addition, I show that recapping decreases the reproductive success of mites by increasing delayed developing female offspring and cells lacking male offspring. By establishing a novel picture-based brood investigation method, I could furthermore show that both the removal of brood cells and recapping activity specifically target brood ages in which mite offspring would be expected. Recapping, however, did not cause infertility of mites. Considering the findings of my first study, this points towards complementary mechanisms. This underlines the importance of increased recapping behaviour and decreased mite reproduction as resistance traits, while at the same time emphasising the challenges of reliable data acquisition. To pave the way for a practical application of these findings in breeding, we then investigated the heritability (i.e., the share of genotypic variation on the observed phenotypic variation) of the accounted traits. By elaborating comparable test protocols and compiling data from over 4,000 colonies, we could, for the first time, demonstrate that recapping of infested cells and decreased reproductive success of mites are heritable (and thus selectable) traits in managed honeybee populations. My thesis proves the importance of recapping and decreased mite reproduction as resistance traits and therefore valuable goals for breeding efforts. In this regard, I shed light on the underlying mechanisms of both traits, and present clear evidence for their interaction and heritability. / Die Westliche Honigbiene (Apis mellifera) zählt zu den anpassungsfähigsten Arten der Welt. Diese Anpassungsfähigkeit liegt in der Zusammenarbeit tausender unterschiedlich spezialisierter Individuen begründet. Auf Volksebene können Bienen, die mit einer bestimmten Aufgabe oder Situation gut umgehen können, andere Individuen, die dies weniger gut können, absichern. Andererseits können Letztere womöglich mit anderen Situationen besser umgehen. Dieses evolutionäre Erfolgskonzept sichert das Überleben der Völker selbst unter herausfordernden Habitatbedingungen. Die ektoparasitäre Milbe Varroa destructor stellt in diesem Zusammenhang weltweit die größte biotische Herausforderung dar. Ohne entsprechende Behandlung siechen die Völker rasch dahin und sterben schlussendlich. In einigen Populationen haben sich jedoch Resistenzmechanismen durch natürliche Selektion herausgebildet, die es den Völkern ermöglichen, ohne Behandlung zu überleben. Die verschiedenen Verhaltensweisen scheinen dabei an die jeweiligen Habitatbedingungen angepasst zu sein und sich gegenseitig zu ergänzen. Was diese Reaktion auf die Milben auslöst und wie sie funktioniert ist allerdings noch weitestgehend unbekannt. Meine Dissertation fokussiert den biologischen Hintergrund von Varroa-resistenzmechanismen bei Honigbienen und stellt dabei wichtige Erkenntnisse zum Verständnis dieser komplexen Parasit-Wirt-Beziehung vor. Darauf aufbauend leite ich Implikationen für die angewandte Bienenzucht und wissenschaftliche Untersuchungen auf dem Gebiet der Varroa-resistenz ab. Hierbei konzentriere ich mich insbesondere auf zwei Merkmale, die häufig in resistenten Völkern zu finden sind: die reduzierte Milbenreproduktion und das Entdeckeln und Wiederverdeckeln bereits verschlossener Brutzellen. Beide Merkmale treten in geringerem Umfang auch in milbenanfälligen Populationen auf und sind daher von besonderem Interesse für jedwede Zuchtbemühung mit dem Ziel der Varroa-resistenz. Durch die Untersuchung von Fehlern in der Reproduktion der Milben, konnte ich diesen Hauptmechanismus der Varroa-resistenz mit Verhaltensweisen der Bienen, sowie äußeren Faktoren in Verbindung setzen. Da die Milbenvermehrung untrennbar mit der Brutaufzucht der Bienen verbunden ist, habe ich zunächst die Einflüsse von Brutunterbrechungen auf den Vermehrungserfolg der Milben untersucht. Diese Untersuchung zeigte auf, dass Brutunterbrechungen den Vermehrungserfolg der Milben sowohl kurzfristig, als auch langfristig herabsetzen. Durch die Untersuchung der jeweils zugrundeliegenden Ursachen gescheiterter Milbenreproduktion konnte ich zeigen, dass dies vor Allem auf einen gesteigerten Anteil infertiler Milben zurückzuführen war. Des Weiteren konnte ich beweisen, dass die Unterbrechung der Brutaufzucht die Ausprägung des Wiederverdeckelns signifikant verstärkte. Folglich zeigten diese Ergebnisse eine dynamische Anpassung der Milbenreproduktion und des Wiederverdeckelns, sowie einen direkten Einfluss der Brutunterbrechungen auf beide Eigenschaften. Um die Plastizität der Ausprägung beider Merkmale genauer zu erklären, untersuchte ich daraufhin drei Jahre lang die Milbenvermehrung, das Verhalten des Wiederverdeckelns, sowie die Befallsentwicklung. Daraus resultierte ein umfangreicher Datensatz, der eine signifikante saisonale Variation der Milbenvermehrung und des Wiederverdeckelns belegte. Ich konnte außerdem eindeutig beweisen, dass das Wiederverdeckeln den Reproduktionserfolg der Milben herabsetzt, indem es die Anteile von verzögert heranwachsenden weiblichen Nachkommen und fehlenden Männchen steigert. Durch Anwendung einer neuartigen Bild-basierten Methode der Brutuntersuchung, konnte ich darüber hinaus zeigen, dass sich sowohl das Ausräumen, als auch das Wiederverdeckeln von Brutzellen auf Brutalter konzentriert, in denen Milbennachwuchs erwartet werden würde. Das Wiederverdeckeln trug jedoch nicht zur Infertilität der Milben bei, was zusammen mit den Ergebnissen meiner ersten Untersuchung auf komplementäre Mechanismen hinweist. Dies unterstreicht die Bedeutung des Wiederverdeckelns und der verminderten Milbenreproduktion als Resistenzmechanismen, hebt aber gleichzeitig auch die Herausforderungen einer verlässlichen Datenerhebung hervor. Um den Weg für die praktische Anwendung dieser Erkenntnisse in der Zuchtarbeit zu ebnen, untersuchten wir daraufhin die Erblichkeit (den Anteil der genotypischen Variation an der beobachteten phänotypischen Variation) der betrachteten Merkmale. Durch das Erarbeiten vergleichbarer Prüfprotokolle und Zusammenführen von Daten aus über 4000 Völkern, konnten wir erstmalig zeigen, dass das Wiederverdeckeln befallener Zellen und der verminderte Vermehrungserfolg der Milben erbliche und damit selektierbare Merkmale in bewirtschafteten Honigbienenpopulationen sind. Meine Dissertation beweist die Relevanz des Wiederverdeckelns und der verminderten Milbenreproduktion als Resistenzmerkmale und damit lohnende Ziele für Zuchtbemühungen. In diesem Zusammenhang beleuchtete ich verschiedene Mechanismen, die der Ausprägung beider Merkmale zugrunde liegen und lieferte eindeutige Beweise für deren Interaktion und Erblichkeit.