蜜蜂瓦螨敏感卫生行为研究进展

蜜蜂具有很高的生态价值和经济价值,对农业生产帮助巨大。然而,狄斯瓦螨Varroa destructor寄生给西方蜜蜂Apis mellifera蜂群造成重大损失,对蜜蜂健康构成严重威胁,因此,狄斯瓦螨的防治变得尤为紧要。虽然化学防治是防治狄斯瓦螨常用且有效措施,但仍存在许多缺点,如造成蜂产品污染、导致蜂螨产生抗药性等。另一方面,培育抗螨蜂种被证明是可持续的狄斯瓦螨防治方法。瓦螨敏感卫生行为(Varroa sensitive hygiene, VSH)是蜜蜂重要的抗螨性状之一。本文从狄斯瓦螨的生活周期、对蜜蜂的危害、蜜蜂抗螨行为、瓦螨敏感卫生行为调控和遗传育种等方面进行综述,为狄斯瓦螨防治和抗螨蜂种选育提供参考。     

Behaviour of Varroa mites invading honey bee brood cells

Invasion behaviour of Varroa jacobsoni into honey bee brood cells was studied using an observation hive. The mites were carried close to a suitable brood cell by the bees. Subsequently, the mites moved from the bees to the rim of the cell, walked quickly inside, crawled between the larva and the cell wall, and moved onto the bottom of the cell. Varroa mites were never seen walking across the comb, and entering and leaving brood cells as has been described for Tropilaelaps clareae. Differences in invasion strategies between V. jacobsoni and T. clareae are discussed.     

Vitellogenesis in Varroa jacobsoni,a parasite of honey bees

Reproduction in Varroa jacobsoni occurs only in cells of the capped honey bee brood. Female mites were sampled at different times after cell sealing and ovaries containing a vitellogenic oocyte of the first gonocycle were examined under an electron microscope. It was found that the cytoplasmic connection between the lyrate organ and the oocyte persists far into the vitellogenic growth phase. In addition, a large amount of yolk material is taken up from the haemolymph. All ultrastructural features characteristic of vitellogenesis, such as microvilli, coated pits, vesicles and growing yolk platelets, are present. If more than four Varroa females live in an overcrowded brood cell, they appear to be in stress conditions and their vitellogenic oocytes may become atretic. Alterations typical for oocyte degradation and oosorption were observed in such situations.     

Host adaptations reduce the reproductive success of Varroa destructor in two distinct European honey bee populations

Honey bee societies (Apis mellifera), the ectoparasitic mite Varroa destructor, and honey bee viruses that are vectored by the mite, form a complex system of host-parasite interactions. Coevolution by natural selection in this system has been hindered for European honey bee hosts since apicultural practices remove the mite and consequently the selective pressures required for such a process. An increasing mite population means increasing transmission opportunities for viruses that can quickly develop into severe infections, killing a bee colony. Remarkably, a few subpopulations in Europe have survived mite infestation for extended periods of over 10 years without management by beekeepers and offer the possibility to study their natural host-parasite coevolution. Our study shows that two of these "natural" honey bee populations, in Avignon, France and Gotland, Sweden, have in fact evolved resistant traits that reduce the fitness of the mite (measured as the reproductive success), thereby reducing the parasitic load within the colony to evade the development of overt viral infections. Mite reproductive success was reduced by about 30% in both populations. Detailed examinations of mite reproductive parameters suggest these geographically and genetically distinct populations favor different mechanisms of resistance, even though they have experienced similar selection pressures of mite infestation. Compared to unrelated control colonies in the same location, mites in the Avignon population had high levels of infertility while in Gotland there was a higher proportions of mites that delayed initiation of egg-laying. Possible explanations for the observed rapid coevolution are discussed.     

Genotypic variability and relationships between mite infestation levels, mite damage, grooming intensity, and removal of Varroa destructor mites in selected strains of worker honey bees (Apis mellifera L.)

The objective of this study was to demonstrate genotypic variability and analyze the relationships between the infestation levels of the parasitic mite Varroa destructor in honey bee (Apis mellifera) colonies, the rate of damage of fallen mites, and the intensity with which bees of different genotypes groom themselves to remove mites from their bodies. Sets of paired genotypes that are presumably susceptible and resistant to the varroa mite were compared at the colony level for number of mites falling on sticky papers and for proportion of damaged mites. They were also compared at the individual level for intensity of grooming and mite removal success. Bees from the "resistant" colonies had lower mite population rates (up to 15 fold) and higher percentages of damaged mites (up to 9 fold) than bees from the "susceptible" genotypes. At the individual level, bees from the "resistant" genotypes performed significantly more instances of intense grooming (up to 4 fold), and a significantly higher number of mites were dislodged from the bees' bodies by intense grooming than by light grooming (up to 7 fold) in all genotypes. The odds of mite removal were high and significant for all "resistant" genotypes when compared with the "susceptible" genotypes. The results of this study strongly suggest that grooming behavior and the intensity with which bees perform it, is an important component in the resistance of some honey bee genotypes to the growth of varroa mite populations. The implications of these results are discussed.     

Asynchronous development of honey bee host and Varroa destructor (Mesostigmata: Varroidae) influences reproductive potential of mites

A high proportion of nonreproductive (NR) Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae), is commonly observed in honey bee colonies displaying the varroa sensitive hygienic trait (VSH). This study was conducted to determine the influence of brood removal and subsequent host reinvasion of varroa mites on mite reproduction. We collected foundress mites from stages of brood (newly sealed larvae, prepupae, white-eyed pupae, and pink-eyed pupae) and phoretic mites from adult bees. We then inoculated these mites into cells containing newly sealed larvae. Successful reproduction (foundress laid both a mature male and female) was low (13%) but most common in mites coming from sealed larvae. Unsuccessful reproductive attempts (foundress failed to produce both a mature male and female) were most common in mites from sealed larvae (22%) and prepupae (61%). Lack of any progeny was most common for mites from white-eyed (83%) and pink-eyed pupae (92%). We also collected foundress mites from sealed larvae and transferred them to cells containing newly sealed larvae, prepupae, white-eyed pupae, or pink-eyed pupae. Successful reproduction only occurred in the transfers to sealed larvae (26%). Unsuccessful reproductive attempts were most common in transfers to newly sealed larvae (40%) and to prepupae (25%). Unsuccessful attempts involved the production of immature progeny (60%), the production of only mature daughters (26%) or the production of only a mature male (14%). Generally, lack of progeny was not associated with mites having a lack of stored sperm. Our results suggest that mites exposed to the removal of prepupae or older brood due to hygiene are unlikely to produce viable mites if they invade new hosts soon after brood removal. Asynchrony between the reproductive status of reinvading mites and the developmental stage of their reinvasion hosts may be a primary cause of NR mites in hygienic colonies. Even if reinvading mites use hosts having the proper age for infestation, only a minority of them will reproduce.     

Winter survival of individual honey bees and honey bee colonies depends on level of Varroa destructor infestation

Background

Recent elevated winter loss of honey bee colonies is a major concern. The presence of the mite Varroa destructor in colonies places an important pressure on bee health. V. destructor shortens the lifespan of individual bees, while long lifespan during winter is a primary requirement to survive until the next spring. We investigated in two subsequent years the effects of different levels of V. destructor infestation during the transition from short-lived summer bees to long-lived winter bees on the lifespan of individual bees and the survival of bee colonies during winter. Colonies treated earlier in the season to reduce V. destructor infestation during the development of winter bees were expected to have longer bee lifespan and higher colony survival after winter.

Methodology/Principal Findings

Mite infestation was reduced using acaricide treatments during different months (July, August, September, or not treated). We found that the number of capped brood cells decreased drastically between August and November, while at the same time, the lifespan of the bees (marked cohorts) increased indicating the transition to winter bees. Low V. destructor infestation levels before and during the transition to winter bees resulted in an increase in lifespan of bees and higher colony survival compared to colonies that were not treated and that had higher infestation levels. A variety of stress-related factors could have contributed to the variation in longevity and winter survival that we found between years.

Conclusions/Significance

This study contributes to theory about the multiple causes for the recent elevated colony losses in honey bees. Our study shows the correlation between long lifespan of winter bees and colony loss in spring. Moreover, we show that colonies treated earlier in the season had reduced V. destructor infestation during the development of winter bees resulting in longer bee lifespan and higher colony survival after winter.     

蜜蜂巢房大小影响狄斯瓦螨的繁殖行为

在具有相同类型幼虫的雄蜂和工蜂巢房中,人工接入狄斯瓦螨Varroa destructorAnderson&Trueman,比较巢房大小不同,对于螨繁殖的影响。结果显示:狄斯瓦螨在具有工蜂幼虫的工蜂房(WW)中的繁殖率为94.4%,而在具有工蜂幼虫的雄蜂房(WD)中繁殖率只有27.7%,差异极显著。在具有工蜂幼虫的工蜂房中,每只雌螨产出后代的平均数为3.35±1.56只;在具有工蜂幼虫的雄蜂房中每只雌螨产出后代的平均数为0.49±0.93只,差异极显著。表明:在具有相同类型幼虫存在的情况下,狄斯瓦螨喜欢较小的巢房,狄斯瓦螨在较小巢房中的繁殖能力明显高于较大的巢房。     

Observation of Varroa destructor behavior in capped worker brood of Africanized honey bees

The behavioral activity of Varroa destructor was observed using transparent cells. Mite oviposition started at 45.0?±?25.0?h post capping, followed by the next eggs laid at regular 27.3?±?2.0?h intervals. On the prepupa, mites were found to feed often and there was no preference for a specific segment as a feeding site. During the pupal stage the mite fed less often and almost always at the same point. Varroa showed a preference for defecation in the posterior part of the cell. A significant association was observed between the position of the feeding point in the pupa and the defecation site on the cell wall. Displacement behavior was observed in 71?% of the infested bee larvae and a major change in the free space available for varroa in the cell occurred when the prepupa molted into a pupa.     

Reproduction of ectoparasitic mites in a coevolved system: Varroa spp.—Eastern honey bees,Apis cerana

Parasite host shifts can impose a high selective pressure on novel hosts. Even though the coevolved systems can reveal fundamental aspects of host–parasite interactions, research often focuses on the new host–parasite relationships. This holds true for two ectoparasitic mite species, Varroa destructor and Varroa jacobsonii, which have shifted hosts from Eastern honey bees, Apis cerana, to Western honey bees, Apis mellifera, generating colony losses of these pollinators globally. Here, we study infestation rates and reproduction of V. destructor and V. jacobsonii haplotypes in 185 A. cerana colonies of six populations in China and Thailand to investigate how coevolution shaped these features. Reproductive success was mostly similar and low, indicating constraints imposed by hosts and/or mite physiology. Infestation rates varied between mite haplotypes, suggesting distinct local co‐evolutionary scenarios. The differences in infestation rates and reproductive output between haplotypes did not correlate with the virulence of the respective host‐shifted lineages suggesting distinct selection scenarios in novel and original host. The occasional worker brood infestation was significantly lower than that of drone brood, except for the V. destructor haplotype (Korea) from which the invasive lineage derived. Whether mites infesting and reproducing in atypical intraspecific hosts (i.e., workers and queens) actually predisposes for and may govern the impact of host shifts on novel hosts should be determined by identifying the underlying mechanisms. In general, the apparent gaps in our knowledge of this coevolved system need to be further addressed to foster the adequate protection of wild and managed honey bees from these mites globally.     

Behavior of varroa mites in worker brood cells of Africanized honey bees

The ectoparasitic mite Varroa destructor is currently the most important pest of the honey bee, Apis mellifera. Because mite reproduction occurs within the sealed cell, the direct observation of varroa activity inside the cell is difficult. A video observation method using transparent polystyrol cells containing infested brood was used to analyze the behavior of varroa mites in worker brood of Africanized honey bees. We recorded how mites feed on the larva and pupa, construct a fecal accumulation site and how the bee larva carried out some longitudinal movements around the cell. The feeding activity of the foundress mite varies during the course of the cycle. On the prepupa mites were found to feed often (0.3 ± 0.2 bouts h⁻¹) for a period of 8.7 ± 8.4 min h⁻¹ and there was no preference for a specific segment as feeding site. On the opposite, during the pupal stage mites fed less often (0.1 ± 0.1 bouts h⁻¹) for a period of 6.2 ± 4.0 min h⁻¹ and almost always at a particular site (92.4%). On pupa, 83.7% of the feeding was on the 2nd abdominal segment (n = 92), and only few perforations were found on the thorax. Varroa shows a preference for defecation in the posterior part of the cell (cell apex), close to the bee′s anal zone. We found a high correlation between the position of the feeding site on the pupa and the position of the fecal accumulation on the cell wall. Most infested cells have only one fecal accumulation site and it was the favorite resting site for the mite, where it spent 24.3 ± 3.9 min h⁻¹. Longitudinal displacements were observed in 28.0% (n = 25) of the analyzed bee larvae. Turning movements around the cell, from the bottom to the top, were carried out by these larvae, mainly during the second day (47.7 ± 22.5 min h⁻¹), just before pupation, with a total time of 874.9 ± 262.2 min day⁻¹ (n = 7 individuals). These results in worker brood of Africanized bees demonstrate adaptations of varroa mites to parasitizing the developing bee inside the capped brood cells.     

Reproduction of Varroa destructor in worker brood of Africanized honey bees (Apis mellifera)

Reproduction and population growth of Varroa destructor was studied in ten naturally infested, Africanized honeybee (AHB) (Apis mellifera) colonies in Yucatan, Mexico. Between February 1997 and January 1998 monthly records of the amount of pollen, honey, sealed worker and drone brood were recorded. In addition, mite infestation levels of adult bees and worker brood and the fecundity of the mites reproducing in worker cells were determined. The mean number of sealed worker brood cells (10,070 ± 1,790) remained fairly constant over the experimental period in each colony. However, the presence and amount of sealed drone brood was very variable. One colony had drone brood for 10 months and another for only 1 month. Both the mean infestation level of worker brood (18.1 ± 8.4%) and adult bees (3.5 ± 1.3%) remained fairly constant over the study period and did not increase rapidly as is normally observed in European honey bees. In fact, the estimated mean number of mites fell from 3,500 in February 1997 to 2,380 in January 1998. In May 2000 the mean mite population in the study colonies was still only 1,821 mites. The fertility level of mites in this study was much higher (83–96%) than in AHB in Brazil(25–57%), and similar to that found in EHB (76–94%). Mite fertility remained high throughout the entire study and was not influenced by the amount of pollen, honey or worker brood in the colonies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic bases of tolerance to Varroa destructor in honey bees (Apis mellifera L.)

Currently, the Varroa destructor mite is the most serious parasite of honey bees (Apis mellifera) and has become a nearly cosmopolitan species. The mite not only causes damage by feeding on the haemolymph of honey bees, but it also transmits viruses, which have been implicated in colony collapse disorder. The major research goal has been to breed mite-tolerant honey bee lines in order to reduce the amount of pesticide used, because pesticides can promote the evolution of resistance in mites. In this review, we describe different behavioural traits and genes that may be part of the defence against the Varroa mite. Specifically, we review grooming behaviour, Varroa-sensitive hygiene and the suppression of mite reproduction. A large number of candidate genes have been identified by Quantitative Trait Loci studies, and through gene expression studies their function and effect have been elucidated. Results from the studies discussed can be used in apiary practice.     

Effects of Imidacloprid and Varroa destructor on survival and health of European honey bees,Apis mellifera

There has been growing concern over declines in populations of honey bees and other pollinators which are a vital part to our food security. It is imperative to identify factors responsible for accelerated declines in bee populations and develop solutions for reversing bee losses. While exact causes of colony losses remain elusive, risk factors thought to play key roles are ectoparasitic mites Varroa destructor and neonicotinoid pesticides. The present study aims to investigate effects of a neonicotinoid pesticide Imidacloprid and Varroa mites individually on survivorship, growth, physiology, virus dynamics and immunity of honey bee workers. Our study provides clear evidence that the exposure to sublethal doses of Imidacloprid could exert a significantly negative effect on health and survival of honey bees. We observed a significant reduction in the titer of vitellogenin (Vg), an egg yolk precursor that regulates the honey bees development and behavior and often are linked to energy homeostasis, in bees exposed to Imidacloprid. This result indicates that sublethal exposure to neonicotinoid could lead to increased energy usage in honey bees as detoxification is a energy‐consuming metabolic process and suggests that Vg could be a useful biomarker for measuring levels of energy stress and sublethal effects of pesticides on honey bees. Measurement of the quantitative effects of different levels of Varroa mite infestation on the replication dynamic of Deformed wing virus (DWV), an RNA virus associated with Varroa infestation, and expression level of immune genes yields unique insights into how honey bees respond to stressors under laboratory conditions.     

Catecholamines affect storage and retrieval of conditioned odour stimuli in honey bees

• 1.1. The effects of injected catecholamines and their analogues on odour learning in honey bees is described.
• 2.2. Dopamine blocks the retrieval of a learned odour signal with a specific time course and does not block the storage of this signal.
• 3.3. Noradrenaline blocks retrieval and storage of a conditioned odour signal.
• 4.4. Amphetamine shows the same effects as noradrenaline.
• 5.5. Haloperidol has no affect on memory retrieval or storage.

     

Transgenerational interactions involving parental age and immune status affect female reproductive success in Drosophila melanogaster

It is well established that the parental phenotype can influence offspring phenotypic expression, independent of the effects of the offspring''s own genotype. Nonetheless, the evolutionary implications of such parental effects remain unclear, partly because previous studies have generally overlooked the potential for interactions between parental sources of non-genetic variance to influence patterns of offspring phenotypic expression. We tested for such interactions, subjecting male and female Drosophila melanogaster of two different age classes to an immune activation challenge or a control treatment. Flies were then crossed in all age and immune status combinations, and the reproductive success of their immune- and control-treated daughters measured. We found that daughters produced by two younger parents exhibited reduced reproductive success relative to those of other parental age combinations. Furthermore, immune-challenged daughters exhibited higher reproductive success when produced by immune-challenged relative to control-treated mothers, a pattern consistent with transgenerational immune priming. Finally, a complex interplay between paternal age and parental immune statuses influenced daughter''s reproductive success. These findings demonstrate the dynamic nature of age- and immune-mediated parental effects, traceable to both parents, and regulated by interactions between parents and between parents and offspring.     

Effect of acaricide resistance on reproductive ability of the honey bee mite Varroa destructor

The reproduction of pyrethroid-resistant Varroa destructor mite, a brood parasite of honey bees, was observed in Weslaco, Texas, and the results compared with known susceptible mite populations from other studies. Seven Apis mellifera colonies that had mite populations resistant to the acaricide Apistan^™ were used. Pyrethroid-resistance was confirmed when only 17% rather than 90% of mites confined in dishes containing Apistan^™ died after 12 h of exposure. The average number of eggs laid by resistant mites invading worker and drone cells was 4.4 and 5.4 respectively. This is similar to the number of eggs laid by susceptible mites in worker (4.4–4.8) or drone (4.7–5.5) cells. Also the average number of fertilised V. destructor female mites produced by resistant mites in worker (1.0) and drone (2.1) cells were similar to the number produced by susceptible mites in worker (0.9) and drone (1.9–2.2) cells. In addition, no major differences between the resistant and susceptible mite populations were observed in either worker or drone cells when six different reproductive categories and offspring mortality rates were compared. Therefore, it appears that there is little or no reproductive fitness cost associated with pyrethroid resistance in V. destructor in Texas. This revised version was published online in July 2006 with corrections to the Cover Date.