Host Specificity in the Honeybee Parasitic Mite,Varroa spp. in Apis mellifera and Apis cerana

The ectoparasitic mite Varroa destructor is a major global threat to the Western honeybee Apis mellifera. This mite was originally a parasite of A. cerana in Asia but managed to spill over into colonies of A. mellifera which had been introduced to this continent for honey production. To date, only two almost clonal types of V. destructor from Korea and Japan have been detected in A. mellifera colonies. However, since both A. mellifera and A. cerana colonies are kept in close proximity throughout Asia, not only new spill overs but also spill backs of highly virulent types may be possible, with unpredictable consequences for both honeybee species. We studied the dispersal and hybridisation potential of Varroa from sympatric colonies of the two hosts in Northern Vietnam and the Philippines using mitochondrial and microsatellite DNA markers. We found a very distinct mtDNA haplotype equally invading both A. mellifera and A. cerana in the Philippines. In contrast, we observed a complete reproductive isolation of various Vietnamese Varroa populations in A. mellifera and A. cerana colonies even if kept in the same apiaries. In light of this variance in host specificity, the adaptation of the mite to its hosts seems to have generated much more genetic diversity than previously recognised and the Varroa species complex may include substantial cryptic speciation.     

Attraction and Repellence of Workers by the Honeybee Queen (Apis mellifera L.)

The spatial distribution of worker honeybees in colonies of two African subspecies ( Apis mellifera capensis and Apis mellifera scutellata ), as well as their natural hybrids, was determined in five observation colonies, each containing one frame. The queens were allowed to roam freely throughout the hive during the initial phase of the experiment, and were observed on both sides of the frame in all colonies. In the second phase of the experiment the queen was caged on one side of the frame in three of the observation colonies, the other two colonies serving as controls. Queen caging significantly affected the distribution of worker bees, with more A. m. scutellata workers being attracted to the queen and more A. m. capensis worker bees being repelled by the presence of the queen. The hybrid workers were also repelled, but to a lesser extent. Queens thus not only attract workers to form a retinue or during swarming but also repel workers in the nest. Evasion of the reproductive suppression by the queen pheromones may be a typical behavior for workers with a high reproductive potential.     

Incidence and Geographical Distribution of Honeybee (Apis mellifera L.) Pests in Jordan

The occurrence and distribution of pests of honeybee (Apis mellifera L.) in Jordan were surveyed during the agricultural seasons of 1999 and 2000. A total of 800 colonies in 112 apiaries were chosen from different geographical regions that support beekeeping in Jordan. Honeybee colonies are attacked by 21 pest species in different areas of Jordan. The most distributed pests which cause considerable damage are Varroa destructor, Vespa orientalis, Galleria melonella, Dorylus fulvus, Braula orientalis, Merops apiaster, Hirundo rustica, Hirundo daurica and Merops orientalis. Other pests of minor importance to beekeeping were also recorded. Most of the recorded pests were appeared in both the Jordan Valley and Irbid regions.     

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.     

Local honeybee (Apis mellifera mellifera L.) populations in the Urals

The COI-COII intergenic region of mitochondrial DNA (mtDNA) was studied in local honeybee (Apis mellifera mellifera) L. populations from the Middle and Southern Urals. Analysis of bee colonies in these regions revealed apiaries enriched in families descending from A. m. mellifera in the maternal lineage. These results confirm the suggestion of preservation of A. m. mellifera refuges in the Urals and provide grounds for work on the preservation of the gene pool of this bee variety, valuable for all Russia.     

Mating Frequencies of Honey Bee Queens (Apis mellifera L.) in a Population of Feral Colonies in the Northeastern United States

Across their introduced range in North America, populations of feral honey bee (Apis mellifera L.) colonies have supposedly declined in recent decades as a result of exotic parasites, most notably the ectoparasitic mite Varroa destructor. Nonetheless, recent studies have documented several wild populations of colonies that have persisted. The extreme polyandry of honey bee queens—and the increased intracolony genetic diversity it confers—has been attributed, in part, to improved disease resistance and may be a factor in the survival of these populations of feral colonies. We estimated the mating frequencies of queens in feral colonies in the Arnot Forest in New York State to determine if the level of polyandry of these queens is especially high and so might contribute to their survival success. We genotyped the worker offspring from 10 feral colonies in the Arnot Forest of upstate New York, as well as those from 20 managed colonies closest to this forest. We found no significant differences in mean mating frequency between the feral and managed queens, suggesting that queens in the remote, low-density population of colonies in the Arnot Forest are neither mate-limited nor adapted to mate at an especially high frequency. These findings support the hypothesis that the hyperpolyandry of honey bees has been shaped on an evolutionary timescale rather than on an ecological one.     

Magnetic parameters of the bees Apis mellifera mellifera (L.) obtained by SQUID-magnetometry

It was found using SQUID-magnetometry that the dependence of the magnetization of a bee on the intensity of the applied magnetic fields has the form of a hysteresis loop. By using the parameters of the loop, the magnetic phases were identified and their characteristics were determined. It was found that the diamagnetic component is significant and has a susceptibility = -1,3335 x 10(-8) Gs x cm3/Oe. The ferromagnetite phase is represented by a multidomain magnetite with the coercive force of 70-80 Oe and magnetic saturation momnts of 4 x 10(-5) EMU (Gs x cm3) and residual moment of 3.07 x 10(-6) EMU.     

An Amino Acid Substitution (L925V) Associated with Resistance to Pyrethroids in Varroa destructor

The Varroa mite, Varroa destructor, is an important pest of honeybees and has played a prominent role in the decline in bee colony numbers over recent years. Although pyrethroids such as tau-fluvalinate and flumethrin can be highly effective in removing the mites from hives, their intensive use has led to many reports of resistance. To investigate the mechanism of resistance in UK Varroa samples, the transmembrane domain regions of the V. destructor voltage-gated sodium channel (the main target site for pyrethroids) were PCR amplified and sequenced from pyrethroid treated/untreated mites collected at several locations in Central/Southern England. A novel amino acid substitution, L925V, was identified that maps to a known hot spot for resistance within the domain IIS5 helix of the channel protein; a region that has also been proposed to form part of the pyrethroid binding site. Using a high throughput diagnostic assay capable of detecting the mutation in individual mites, the L925V substitution was found to correlate well with resistance, being present in all mites that had survived tau-fluvalinate treatment but in only 8 % of control, untreated samples. The potential for using this assay to detect and manage resistance in Varroa-infected hives is discussed.     

The mating behaviour of the honeybee (Apis mellifera L.)

An account is given of the mating responses of free-flying drones towards a queen, and of the pheromones controlling these responses.     

Nest Defense Behavior in Colonies from Crosses Between Africanized and European Honey Bees (Apis mellifera L.) (Hymenoptera: Apidae)

Honey bee (Apis mellifera L.) colonies with either European or Africanized queens mated to European or Africanized drones alone or in combination were tested for defensive behavior using a breath test. The most defensive colonies were those with European or Africanized queens mated to Africanized drones. In colonies where both European and Africanized patrilines existed, most of the workers participating in nest defense behavior for the first 30 s after a disturbance were of African patrilines. Nest defense behavior appears to be genetically dominant in honey bees.     

Response of foster Asian honeybee (Apis cerana Fabr.) colonies to the brood of European honeybee (Apis mellifera L.) infested with parasitic mite,Varroa jacobsoni oudemans

The response of Asian honeybee (Apis cerana Fabr.) colonies toward the introduced worker brood of the European honeybee (Apis mellifera L.) infested with the parasitic mite Varroa jacobsoni Oudemans was investigated. When no mites were present, 40% of the healthy open brood and 3% of the healthy capped brood of the European honeybees were rejected by the Asian honeybee colonies. When the brood was infested, brood rejection was significantly higher for open (P < 0.05) and capped broods (P < 0.01). The brood removal activity decreased with time. The quantity of brood removed was also correlated with mite infestation level for open (r² = 0.933) and sealed broods (r² = 0.918). The feasibility of using heterospecific colonies to control Varroa mite is unclear and is discussed from behavioral and ecological points of view.     

Age at Which Larvae Are Orphaned Determines Their Development into Typical or Rebel Workers in the Honeybee (Apis mellifera L.)

In the honeybee, diploid larvae fed with royal jelly develop into reproductive queens, whereas larvae fed with royal jelly for three days only and subsequently with honey and pollen develop into facultatively sterile workers. A recent study showed that worker larvae fed in a queenless colony develop into another female polyphenic form: rebel workers. These rebel workers are more queenlike and have greater reproductive potential than normal workers. However, it was unclear whether larvae orphaned at any time during their feeding period can develop into rebels. To answer this question, the anatomical features of newly emerged workers reared in queenless conditions at different ages during the larval period were evaluated. Our results showed that larvae orphaned during the final four or more days of their feeding life develop into rebel workers with more ovarioles in their ovaries, smaller hypopharyngeal glands, and larger mandibular and Dufour’s glands compared with typical workers with low reproductive potential that were reared with a queen or orphaned at the third to last or a later day of feeding life.     

微孢子虫和狄斯瓦螨分别侵染后的意蜂血淋巴蛋白质含量变化

微孢子虫Nosema apis和狄斯瓦螨微孢子虫Nosema apis和狄斯瓦螨 Varroa destructor (Acari: Varroidae)均为危害意蜂Apis mellifera的重要寄生虫,该文对其危害后意蜂血淋巴蛋白质含量的变化进行了研究。用考马斯亮蓝法测定了意蜂受侵染后血淋巴的蛋白质总量,并用高压超薄层等电点聚焦法进行血淋巴蛋白质分类。结果显示,病蜂血淋巴蛋白质总量,在人工感染微孢子虫后1～10天呈微孢子虫Nosema apis和狄斯瓦螨 Varroa destructor (Acari: Varroidae)均为危害意蜂Apis mellifera的重要寄生虫,该文对其危害后意蜂血淋巴蛋白质含量的变化进行了研究。用考马斯亮蓝法测定了意蜂受侵染后血淋巴的蛋白质总量,并用高压超薄层等电点聚焦法进行血淋巴蛋白质分类。结果显示,病蜂血淋巴蛋白质总量,在人工感染微孢子虫后1～10天呈上升趋势,然后逐渐下降,感染后12～27天保持在感染前意蜂血淋巴总蛋白质含量水平以下。螨侵染后意蜂血淋巴蛋白质含量明显增高,与健康意蜂相比差异极显著。高压超薄层等电点聚焦分析表明：狄斯瓦螨自然侵染意蜂后,意蜂血淋巴蛋白质组分与健康对照组相比发生了明显改变。这些结果提示,意蜂对于微孢子虫或狄斯瓦螨的侵染产生了一定的免疫反应。     

In Situ Hybridization Analysis of the Expression of Futsch,Tau, and MESK2 Homologues in the Brain of the European Honeybee (Apis mellifera L.)

Background

The importance of visual sense in Hymenopteran social behavior is suggested by the existence of a Hymenopteran insect-specific neural circuit related to visual processing and the fact that worker honeybee brain changes morphologically according to its foraging experience. To analyze molecular and neural bases that underlie the visual abilities of the honeybees, we used a cDNA microarray to search for gene(s) expressed in a neural cell-type preferential manner in a visual center of the honeybee brain, the optic lobes (OLs).

Methodology/Principal Findings

Expression analysis of candidate genes using in situ hybridization revealed two genes expressed in a neural cell-type preferential manner in the OLs. One is a homologue of Drosophila futsch, which encodes a microtubule-associated protein and is preferentially expressed in the monopolar cells in the lamina of the OLs. The gene for another microtubule-associated protein, tau, which functionally overlaps with futsch, was also preferentially expressed in the monopolar cells, strongly suggesting the functional importance of these two microtubule-associated proteins in monopolar cells. The other gene encoded a homologue of Misexpression Suppressor of Dominant-negative Kinase Suppressor of Ras 2 (MESK2), which might activate Ras/MAPK-signaling in Drosophila. MESK2 was expressed preferentially in a subclass of neurons located in the ventral region between the lamina and medulla neuropil in the OLs, suggesting that this subclass is a novel OL neuron type characterized by MESK2-expression. These three genes exhibited similar expression patterns in the worker, drone, and queen brains, suggesting that they function similarly irrespective of the honeybee sex or caste.

Conclusions

Here we identified genes that are expressed in a monopolar cell (Amfutsch and Amtau) or ventral medulla-preferential manner (AmMESK2) in insect OLs. These genes may aid in visualizing neurites of monopolar cells and ventral medulla cells, as well as in analyzing the function of these neurons.     

Interadult feeding of jelly in honeybee (Apis mellifera L.) colonies

Summary Honeybee nurses (8 days old) were injected with ¹⁴C-phenylalanine. These bees then dispensed the ¹⁴C-labelled protein-rich products of their hypopharyngeal glands to the queen and the brood, and also to young drones and workers of all age classes. In small colonies containing 400–800 bees, nearly one-quarter of the radioactivity which could not be recovered in the nurses was fed by them in a protein-bound form to other members of the worker caste. During one night, one nurse fed an average of 4–5 foragers with proteinaceous food. The role of nurses in the work allotment system of honeybee colonies therefore needs a new, extended definition. Nurses are largely responsible for preparing nutrients from pollen, which is difficult to digest. They then distribute the nutritionally valuable protein produced by their hypopharyngeal glands to practically all hive mates.Dedicated to Professor Dr. O. Kepka on the occasion of his 65th birthday     

Analysis of GABAergic and Non-GABAergic Neuron Activity in the Optic Lobes of the Forager and Re-Orienting Worker Honeybee (Apis mellifera L.)

Background

European honeybee (Apis mellifera L.) foragers have a highly developed visual system that is used for navigation. To clarify the neural basis underlying the highly sophisticated visual ability of foragers, we investigated the neural activity pattern of the optic lobes (OLs) in pollen-foragers and re-orienting bees, using the immediate early gene kakusei as a neural activity marker.

Methodology/Principal Findings

We performed double-in situ hybridization of kakusei and Amgad, the honeybee homolog of the GABA synthesizing enzyme GAD, to assess inhibitory neural activity. kakusei-related activity in GABAergic and non-GABAergic neurons was strongly upregulated in the OLs of the foragers and re-orienting bees, suggesting that both types of neurons are involved in visual information processing. GABAergic neuron activity was significantly higher than non-GABAergic neuron activity in a part of the OLs of only the forager, suggesting that unique information processing occurs in the OLs of foragers. In contrast, GABAergic neuron activity in the antennal lobe was significantly lower than that of GABAergic neurons in the OLs in the forager and re-orienting bees, suggesting that kakusei-related visual activity is dominant in the brains of these bees.

Conclusions/Significance

The present study provides the first evidence that GABAergic neurons are highly active in the OL neurons of free-moving honeybees and essential clue to reveal neural basis of the sophisticated visual ability that is equipped in the small and simple brain.     

Effect of a lactic acid treatment during winter in temperate climate upon Varroa jacobsoni Oud. and the bee (Apis mellifera L.) colony

Three groups of bee colonies were treated with lactic acid, the pesticide Perizin or lactic acid and Perizin in order to validate the applicability of lactic acid in Varroa mite control. The lactic acid treatment was conducted during winter. Eight ml of lactic acid (15%) per comb side were applied with a dosage gun. The treatment was highly efficient and 94.2%–99.8% of the mites in a colony were killed. Due to precise dosage the lactic acid treatment caused less bee mortality than a treatment with the pesticide Perizin. A lactic acid treatment at-0.2°C caused bee mortality comparable to a Perizin treatment. The number of queen losses after lactic acid treatment and after Perizin treatment was comparable. The number of bees, the size of the brood area, the amount of stored honey and Nosema infestation rates were not significantly different in lactic acid treated colonies and Perizin treated colonies in spring after treatment.