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32 results for “Varroa destructor”

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dryad28/100

Juvenile hormone pathway in honey bee larvae: a source of possible signal molecules for the reproductive behavior of Varroa destructor

The parasitic mite Varroa destructor devastates honey bee (Apis mellifera) colonies around the world. Entering a brood cell shortly before capping, the Varroa mother feeds on the honey bee larvae. The hormones 20-hydroxyecdysone (20E) and juvenile hormone (JH), acquired from the host, have been considered to play a key role in initiating Varroa's reproductive cycle. This study focuses on differential expression of the genes involved in the biosynthesis of JH and ecdysone at 6 time points during the first 30 hours after cell capping in both drone and worker larvae of A. mellifera. This time frame, covering the conclusion of the honey bee brood cell invasion and the start of Varroa's ovogenesis, is critical to the successful initiation of a reproductive cycle. Our findings support a later activation of the ecdysteroid cascade in honey bee drones compared to worker larvae, which could account for the increased egg production of Varroa in A. mellifera drones. The JH pathway was generally downregulated confirming its activity is antagonistic to the ecdysteroid pathway during the larva development. Nevertheless, the genes involved in JH synthesis revealed an increased expression in drones. The upregulation of jhamt gene involved in methyl farnesoate (MF) synthesis came into attention since the MF is not only a precursor of JH but it is also an insect pheromone in its own right as well as JH-like hormone in Acari. This could indicate a possible kairomone effect of MF for attracting the mites into the drone brood cells, along with its potential involvement in ovogenesis after the cell capping, stimulating Varroa's initiation of egg laying.

opencc-zeroNov 2021View details →

dryad28/100

Data for synergistic and antagonistic interactions between Varroa destructor mites and neonicotinoid insecticides in male Apis mellifera honey bees

Pressures from multiple, sometimes interacting, stressors can have negative consequences to important ecosystem-service providing species like the western honey bee (Apis mellifera). The introduced parasite Varroa destructor and the neonicotinoid class of insecticides each represent important, nearly ubiquitous biotic and abiotic stressors to honey bees, respectively. Previous research demonstrated that they can synergistically interact to negatively affect non-reproductive honey bee female workers, but no data exist on how concurrent exposure may affect reproductive honey bee males (drones). This is important, given that the health of reproductive females (queens), possibly because of poor mating, is frequently cited as a major driver of honey bee colony loss. To address this, known age cohorts of drones were obtained from 12 honey bee colonies – seven were exposed to field-relevant concentrations of two neonicotinoids (4.5 ppb thiamethoxam and 1.5 ppb clothianidin) during development via supplementary pollen patties; five colonies received patties not spiked with neonicotinoids. Artificially emerged drones were assessed for natural V. destructor infestation, weighed, and then allocated to the following treatment groups: 1. Control, 2. V. destructor only, 3. Neonicotinoid only, and 4. Combined (both mites and neonicotinoid). Adult drones were maintained in laboratory cages alongside attendant workers (1 drone : 2 worker ratio) until they have reached sexual maturity after 14 days so sperm concentration and viability could be assessed. The data that V. destructor and neonicotinoids interacted synergistically to negatively affect adult drone survival, but that they interacted antagonistically on emergence mass. Although sample sizes were too low to assess the effects of V. destructor and combined exposure on sperm quality, we observed no influence of neonicotinoids on sperm concentration or viability. Our findings highlight the diverse effects of concurrent exposure to stressors on honey bees, and suggest that V. destructor and neonicotinoids can severely effect the number of sexually mature adult drones available for mating.

opencc-zeroOct 2021View details →

dryad28/100

Recapping behavior in Apis cerana: does it contribute to resistance against Varroa destructor?

The invasion of the ectoparasitic mite Varroa destructor in the European honey bee, Apis mellifera, populations has led to the collapse of most wild stocks and to economic losses in beekeeping operations. Understanding how some A. mellifera populations survive infestations by this parasite is of high fundamental and practical interest and has led to numerous studies of potential resistance mechanisms. One of these mechanisms is the uncapping and recapping of comb cells containing infested individuals by nurse bees. Recapping was observed in most surviving populations, but its link to V. destructor resistance remains unclear. Investigating the occurrence of recapping in the Eastern honey bee, Apis cerana, the original host of the parasite, could provide a better understanding of the evolution and function of this behaviour in the genus Apis. We here determined the frequency of recapping in two A. cerana populations in China and Thailand and compared them with a sympatric A. mellifera population in China. The species, which differ in their susceptibility to infestations, did not show significant differences in recapping frequency. A specific association between recapping and resistance to V. destructor in A. cerana is thus not supported. We discuss possible evolution scenarios and functions for this behaviour.

opencc-zeroMar 2023View details →

dryad28/100