Asian Honey Bee Apis Research Articles

Varroa destructor: how does it harm Apis mellifera honey bees and what can be done about it?

Since its migration from the Asian honey bee (Apis cerana) to the European honey bee (Apis mellifera), the ectoparasitic mite Varroa destructor has emerged as a major issue for beekeeping worldwide. Due to a short history of coevolution, the host–parasite relationship between A. mellifera and V. destructor is unbalanced, with honey bees suffering infestation effects at the individual, colony and population levels. Several control solutions have been developed to tackle the colony and production losses due to Varroa, but the burden caused by the mite in combination with other biotic and abiotic factors continues to increase, weakening the beekeeping industry. In this synthetic review, we highlight the main advances made between 2015 and 2020 on V. destructor biology and its impact on the health of the honey bee, A. mellifera. We also describe the main control solutions that are currently available to fight the mite and place a special focus on new methodological developments, which point to integrated pest management strategies for the control of Varroa in honey bee colonies.

Biology and Management of Varroa destructor (Mesostigmata: Varroidae) in Apis mellifera (Hymenoptera: Apidae) Colonies

Abstract Varroa mite (Varroa destructor Anderson and Trueman) infestation of European honey bee (Apis mellifera L.) colonies has been a growing cause of international concern among beekeepers throughout the last 50 yr. Varroa destructor spread from the Asian honey bee (Apis cerana Fabricius [Hymenoptera: Apidae]) to A. mellifera populations in Europe in the 1970s, and subsequently traveled to the Americas. In addition to causing damage through feeding upon lipids of larval and adult bees, V. destructor also facilitates the spread of several viruses, with deformed wing virus being most prevalent. Several sampling methods have been developed for estimating infestation levels of A. mellifera colonies, and acaricide treatments have been implemented. However, overuse of synthetic acaricides in the past has led to widespread acaricide resistant V. destructor populations. The application of Integrated Pest Management (IPM) techniques is a more recent development in V. destructor control and is suggested to be more effective than only using pesticides, thereby posing fewer threats to A. mellifera colonies. When using IPM methods, informed management decisions are made based upon sampling, and cultural and mechanical controls are implemented prior to use of acaricide treatments. If acaricides are deemed necessary, they are rotated based on their mode of action, thus avoiding V. destructor resistance development.

Whole Genome Sequencing and Assembly of the Asian Honey Bee Apis dorsata.

The Asian honey bee (Apis dorsata) is distinct from its more widely distributed cousin Apis mellifera by a few key characteristics. Most prominently, A. dorsata, nest in the open by forming a colony clustered around the honeycomb, whereas A. mellifera nest in concealed cavities. Additionally, the worker and reproductive castes are all of the same size in A. dorsata. In order to investigate these differences, we performed whole genome sequencing of A. dorsata using a hybrid Oxford Nanopore and Illumina approach. The 223 Mb genome has an N50 of 35 kb with the largest scaffold of 302 kb. We have found that there are many genes in the dorsata genome that are distinct from other hymenoptera and also large amounts of transposable elements, and we suggest some candidate genes for A. dorsata’s exceptional level of defensive aggression.

The role of honey hunting in supporting subsistence livelihoods in Sumbawa, Indonesia

AbstractHoney from the giant Asian honey bee (Apis dorsata) has been harvested by communities throughout Southeast Asia for centuries. In Indonesia, 80 per cent of the national supply of honey comes from Sumbawa; however, there is limited information regarding the sustainability and importance of honey hunting in supporting rural livelihoods. This study used semi‐structured interviews and questionnaires to examine honey hunting and forest honey production in Sumbawa. It evaluates the economic and cultural importance, opportunities, and constraints of honey hunting and prompts us to suggest that income generation from honey plays a critical role in supporting rural communities. Of respondents, 83 per cent reported that income from honey was essential and accounts for 68 per cent of cash income. Yet honey hunters were harvesting using destructive methods under dangerous conditions and are subject to unpredictable market prices and fluctuating yields. Unlike situations in other areas of Indonesia, no system of customary law was found to exist that defines ownership of honey trees and the right to harvest from them. Limited access to market information, high moisture content of honey, and limited training and extension services were identified as key constraints. Future research exploring the sustainability of harvesting practices and mechanisms for improving profitability of honey hunters would be valuable.

Reproduction of Distinct Varroa destructor Genotypes on Honey Bee Worker Brood.

Honey bees play important roles in pollination for many crops and wild plants, but have been facing great threats posed by various pathogens and parasites. Among them, Varroa destructor, an obligate ectoparasite of honey bees, is considered the most damaging. Within the last century, V. destructor shifted from the original host, the Asian honey bee Apis cerana to the new host, the European honey bee A. mellifera. However, the reproduction of Varroa mites, especially of different haplotypes in the two hosts, is still largely unknown. In this study, we first investigated the existing Varroa haplotypes in local colonies in southern China, and then compared the reproduction of different haplotypes on the worker brood of both the original and new hosts by artificial inoculation. We confirmed that there are two haplotypes of V. destructor in southern China, one is the Korea haplotype and the other is the China haplotype, and the two types parasitized different honey bee species. Although Varroa females from A. mellifera (Korea haplotype) are able to reproduce on the worker brood of both honey bee species, they showed better reproductive performance in the new host A. mellifera with significantly higher fecundity (number of offspring per mother mite) and reproductive rate (number of adult daughters per mother mite), suggesting that this parasite gains higher fitness after host shift. The data further showed that a short stay of Varroa females inside the A. cerana worker cells decreased their fecundity and especially the reproductive rate in a time-dependent manner, suggesting that the A. cerana worker cells may inhibit Varroa reproduction. In contrast, Varroa mites derived from A. cerana colonies (China haplotype) were entirely sterile in A. mellifera worker cells during two sequential inoculations, while the control mites from A. mellifera colonies (Korea haplotype) reproduced normally. In addition, all the infertile mites were found to defecate on the abdomen of bee pupae. We have revealed that two haplotypes of V. destructor exhibit differential reproduction on the worker brood of the original and new host honey bees, providing novel insights into the diversity and complexity of the reproduction of V. destructor.

Jasa penyerbukan serangga pengunjung bunga pada pertanaman stroberi di Ciwidey, Bandung

Stroberi (Fragaria x ananassa Duch.) merupakan tanaman hortikultura yang penyerbukannya sebagian tergantung pada serangga. Studi dilaksanakan pada pertanaman stroberi di Ciwidey-Bandung, dengan tujuan untuk memperkirakan kontribusi dari serangga pengunjung bunga terhadap kesuksesan penyerbukan stroberi. Di dalam studi ini kontribusi tersebut dinilai dari kelimpahan spesies serangga pengunjung bunga dan durasi kunjungan pada bunga, serta efisiensi penyerbukan yang diukur dari jumlah akene yang berkembang, bobot, dan ukuran buah, serta waktu matang buah. Hasil studi menunjukkan terdapat empat spesies serangga pengunjung bunga stroberi yang paling umum dijumpai, yaitu dua lalat bunga Episyrphus balteatus (Deg.) (47,3%) dan Melanostoma sp. (33,8%); serta dua lebah Lasioglossum sp. (7,0%) dan Apis cerana Fabricius (5,3%). Durasi kunjungan pada setiap bunga oleh kelompok lalat bunga berlangsung 7,75–10,00 menit, sedangkan oleh kelompok lebah 0,25–0,79 menit. Buah stroberi yang berkembang dari bunga yang mendapat kunjungan tunggal oleh setiap spesies serangga menghasilkan buah dengan jumlah akene berkembang 1,6–1,8 kali lipat lebih banyak, bobot buah 1,8–2,3 kali lipat lebih berat, diameter buah 1,2–1,3 kali lipat lebih lebar, serta waktu matang buah 1–3 hari lebih singkat, dibandingkan dengan buah yang berasal dari bunga yang tidak dikunjungi serangga. Keberadaan lebah dan lalat bunga memberikan sumbangan yang penting terhadap penyerbukan pertanaman stroberi di Ciwidey. Temuan dari penelitian ini berimplikasi terhadap peningkatan hasil panen stroberi melalui pengelolaan serangga penyerbuk.

Selection for barriers between honey bees and a devastating parasite.

Rivaling pesticides and a dearth of flowers, the parasitic mite Varroa destructor presents a tremendous threat to western honey bees, Apis mellifera. A longstanding, but minor, pest for the Asian honey bee Apis cerana, these obligate bee parasites feast on developing and adult A.mellifera across several continents. Varroa reproduction is limited to a short window when developing bee pupae are concealed in wax cells. Mated females target developing bees just before pupation and then have about one day to initiate reproduction, eventually laying one male and up to several female offspring. Female mites often fail to reproduce at all, instead waiting in cells until their bee host finishes development and then hitching dangerous rides on a succession of adult bees for up to several weeks, before scouting for a new host pupa. In this issue of Molecular Ecology, Conlon et al. (2019) have explored mite reproductive success via a clever and thought-provoking association study. In so doing, they have identified a protein whose actions could be integral to the dance between bees and their mite parasites.

Pesticide induced visual abnormalities in Asian honey bees (Apis cerana L.) in intensive agricultural landscapes

Pesticide stress is one of the important factors for global bee declines. Apart from physiological and developmental anomalies, pesticides also impose cognitive damages on bees. The present study investigates the visual acuity of wild populations of honey bees, in an agricultural intensification landscape, and corroborates the findings with controlled laboratory experiments. Even though overall morphometric examinations revealed no significant differences between the populations, correct color choices by bees in pesticide exposed populations were significantly reduced. The study reports, for the first time, the significant reduction in ommatidia facet diameter in these populations, as viewed under scanning electron microscope, along with the molecular underpinnings to these findings. Western blot studies revealed a significant reduction in expression of two visual proteins – blue-sensitive opsin and rhodopsin – in the pesticide exposed populations in both field and laboratory conditions. The novel findings from this study form the basis for further investigations into the effects of field realistic doses of multiple pesticide exposures on wild populations of honey bees.

Invasive population establishment of Asian honeybee Apis cerana

Bees, wasps, and ants are among the most highly invasive social insects. Theoretically, the single-locus complementary sex determination (sl-CSD) would hinder the establishment of invasive population with limited founders. Apis cerana has colonized many regions with anthropogenic movement, with devastating effects on the commercial A. mellifera. Here, we summarized the distribution and sex determination mechanism of A. cerana, the recent research results about the invasive A. cerana in Australia, and analyzed how they counteracted the handicap of their sex determination system by the queen's extreme polyandry, worker's reproduction, balancing selection and thelytoky. The knowledge reviewed here could be used as the reference to reveal the establishment mechanism of invasive populations of related social insects.

Beekeeping With the Asian Honey Bee (Apis cerana javana Fabr) in the Indonesian Islands of Java, Bali, Nusa Penida, and Sumbawa

Beekeeping has been practiced throughout Indonesia for many centuries and plays an important, though under-recognized role in contributing to the livelihoods and cultural heritage for many indigeno...

Some morphological aspects of Asian honey bee (Apis cerana) and isolation of its melittin content

Melittin is a major component of honey bee venom that has many biological effects including anticancer properties. The melittin content of Asian honey bee (Apis cerana F.) venom was isolated and quantify by reversed phase-high performance liquid chromatography (RP-HLPC) in Bangladesh. Melittin content was found to present in 59.3% of total venom content in Asian honey bee venom. Venom compounds were investigated at 254 nm and the retention time of venom-melittin was compared with an external standard (Sigma-Aldrich). This finding was compared with previously published findings. By comparing the present data with the earlier studied findings, a projection has been made on the quantification of melittin compound.J. Biodivers. Conserv. Bioresour. Manag. 2017, 3(2): 77-84

Isolation and identification of Lactobacillus bacteria found in the gastrointestinal tract of the dwarf honey bee, Apis florea Fabricius, 1973 (Hymenoptera: Apidae)

Recent research in bacteria-insect symbiosis has shown that lactic acid bacteria (LAB) establish symbiotic relationships with several Apis species. The current study was carried out to isolate and identify Lactobacillus bacteria housed in the gastrointestinal tract of the Asian dwarf honey bee (Apis florea), which is distributed in different regions of Iran. The current study was performed using 100 Gram-stained isolates, which were tested for catalase activity. Bacterial universal primers were used to amplify 16S rDNA genes isolated from bacterial colonies. Sequencing was done for 16S rDNA genes isolated from 43 bacteria. The phylogenetic analyses demonstrated that Lactobacillus flora found in the gastrointestinal tract of A. florea encompassed eight different phenotypes classified as three different species: L. kunkeei, L. plantarum, and L. apis. According to the specific association between bacteria and A. florea, we classified the Apis populations into three zones. Furthermore, the association of L. plantarum with insects foraging in citrus orchards might be explained by differences in nectar and pollen components resulting in the growth of different species of bacteria.

Chronic Nosema ceranae infection inflicts comprehensive and persistent immunosuppression and accelerated lipid loss in host Apis mellifera honey bees

Nosema ceranae is an intracellular microsporidian parasite of the Asian honey bee Apis cerana and the European honey bee Apis mellifera. Until relatively recently, A. mellifera honey bees were naïve to N. ceranae infection. Symptoms of nosemosis, or Nosema disease, in the infected hosts include immunosuppression, damage to gut epithelium, nutrient and energetic stress, precocious foraging and reduced longevity of infected bees. Links remain unclear between immunosuppression, the symptoms of nutrient and energetic stress, and precocious foraging behavior of hosts. To clarify physiological connections, we inoculated newly emerged A. mellifera adult workers with N. ceranae spores, and over 21 days post inoculation (21 days pi), gauged infection intensity and quantified expression of genes representing two innate immune pathways, Toll and Imd. Additionally, we measured each host’s whole-body protein, lipids, carbohydrates and quantified respirometric and activity levels. Results show sustained suppression of genes of both humorally regulated immune response pathways after 6 days pi. At 7 days pi, elevated protein levels of infected bees may reflect synthesis of antimicrobial peptides from an initial immune response, but the lack of protein gain compared with uninfected bees at 14 days pi may represent low de novo protein synthesis. Carbohydrate data do not indicate that hosts experience severe metabolic stress related to this nutrient. At 14 days pi infected honey bees show high respirometric and activity levels, and corresponding lipid loss, suggesting lipids may be used as fuel for increased metabolic demands resulting from infection. Accelerated lipid loss during nurse honey bee behavioral development can have cascading effects on downstream physiology that may lead to precocious foraging, which is a major factor driving colony collapse.

Genomic and transcriptomic analysis of the Asian honeybee Apis cerana provides novel insights into honeybee biology

The Asian honeybee Apis cerana is one of two bee species that have been commercially kept with immense economic value. Here we present the analysis of genomic sequence and transcriptomic exploration for A. cerana as well as the comparative genomic analysis of the Asian honeybee and the European honeybee A. mellifera. The genome and RNA-seq data yield new insights into the behavioral and physiological resistance to the parasitic mite Varroa the evolution of antimicrobial peptides, and the genetic basis for labor division in A. cerana. Comparison of genes between the two sister species revealed genes specific to A. cerana, 54.5% of which have no homology to any known proteins. The observation that A. cerana displayed significantly more vigilant grooming behaviors to the presence of Varroa than A. mellifera in conjunction with gene expression analysis suggests that parasite-defensive grooming in A. cerana is likely triggered not only by exogenous stimuli through visual and olfactory detection of the parasite, but also by genetically endogenous processes that periodically activates a bout of grooming to remove the ectoparasite. This information provides a valuable platform to facilitate the traits unique to A. cerana as well as those shared with other social bees for health improvement.

Foraging behaviour of asiatic honey bee Apis cerana indica (F.) during summer in Madurai, Tamil Nadu

Foraging behaviour of asiatic honey bee <i>Apis</i> <i>cerana</i> <i>indica</i> (F.) during summer in Madurai, Tamil Nadu

The pesticide flupyradifurone impairs olfactory learning in Asian honey bees (Apis cerana) exposed as larvae or as adults

Relatively little attention has focused on how pesticides may affect Asian honey bees, which provide vital crop pollination services and are key native pollinators. We therefore studied the effects of a relatively new pesticide, flupyradifurone (FLU), which has been developed, in part, because it appears safer for honey bees than neonicotinoids. We tested the effects of FLU on Apis cerana olfactory learning in larvae (lower dose of 0.033 µg/larvae/day over 6 days) and, in a separate experiment, adults (lower dose of 0.066 µg/adult bee/day) at sublethal, field-realistic doses given over 3 days. A worst-case field-realistic dose is 0.44 µg/bee/day. Learning was tested in adult bees. The lower larval dose did not increase mortality, but the lower adult dose resulted in 20% mortality. The lower FLU doses decreased average olfactory learning by 74% (larval treatment) and 48% (adult treatment) and reduced average memory by 48% (larval treatment) and 22% (adult treatment) as compared to controls. FLU at higher doses resulted in similar learning impairments. The effects of FLU, a pesticide that is reported to be safer than neonicotinoids for honey bees, thus deserve greater attention.

Acute bee paralysis virus occurs in the Asian honey bee Apis cerana and parasitic mite Tropilaelaps mercedesae

Viruses, and especially RNA viruses, constantly change and adapt to new host species and vectors, posing a potential threat of new and reemerging infectious diseases. Honey bee Acute bee paralysis virus (ABPV) and Deformed wing virus (DWV) are two of the most common honey bee viruses found in European honey bees Apis mellifera and have been implicated in worldwide Varroa-associated bee colony losses. Previous studies have shown that DWV has jumped hosts several times in history causing infection in multiple host species. In the present study, we show that DWV infection could be detected in the Asian honey bee, A. cerana, and the parasitic mite Tropilaelaps mercedesae, confirming previous findings that DWV is a multi-host pathogen and supporting the notion that the high prevalence of DWV in honey bee host populations could be attributed to the high adaptability of this virus. Furthermore, our study provides the first evidence that ABPV occurs in both A. cerana and T. mercedesae in northern Thailand. The geographical proximity of host species likely played an important role in the initial exposure and the subsequent cross-species transmission of these viruses. Phylogenetic analyses suggest that ABPV might have moved from T. mercedesae to A. mellifera and to A. cerana while DWV might have moved in the opposite direction from A. cerana to A. mellifera and T. mercedesae. This result may reflect the differences in virus life history and virus-host interactions, warranting further investigation of virus transmission, epidemiology, and impacts of virus infections in the new hosts. The results from this study indicate that viral populations will continue to evolve and likely continue to expand host range, increasing the need for effective surveillance and control of virus infections in honey bee populations.

Chinese Sacbrood virus infection in Asian honey bees (Apis cerana cerana) and host immune responses to the virus infection.

Chinese Sacbrood virus (CSBV) is a positive-stranded RNAvirus that infects both the European honey bee (Apis mellifera) and the Asian honey bee (A. cerana). However, CSBV has much more devastating effects on Asian honey bees than on European honey bees, posing a serious threat to the agricultural and natural ecosystems that rely on A. cerana for pollination service. Using quantitative RT-PCR method, we conducted studies to examine the CSBV infection in Asian honey bee colonies and immune responses of individual bees in response to CSBV infection. Our study showed that CSBV could cause infection in different developmental stages of workers including eggs, larvae, pupae, newly emerged workers, and foraging workers. In addition, evaluating the tissue tropism and transmission of CSBV in infected bees showed that CSBV was detected in the ovaries, spermatheca, and feces of queens as well as semen of drones of the same colonies, suggesting an existence of vertical transmission of CSBV in Asian honey bees. Further, the detection of CSBV in colony food suggests that healthy bees could pick the infection by the virus-contaminated food, and therefore, a possible existence of a food-borne transmission pathway of CSBV in Asian bee colonies. The expression analysis of transcripts (defensin, abaecin, apidaecin, and hymenoptaecin) involving innate antiviral immune pathways showed that CSBV infection could induce significant immune responses in infected bees. However, the immune responses to CSBV infection varied among different development stages with eggs exhibiting the lowest level of immune expression and forager workers exhibiting the highest level of immune gene expression. The results obtained in the study yield important insights into the mechanisms underlying disease pathogenesis of CSBV infections in Asian honey bees and provide valuable information for a rational design of disease control measures.

Breeding system and pollination of two closely related bamboo species.

An understanding of the breeding systems and pollination of agriculturally important plants is critical to germplasm improvement. Breeding system characteristics greatly influence the amount and spatial distribution of genetic variation within and amongst populations and influence the rarity and extinction vulnerability of plant species. Many woody bamboos have a long vegetative period (20-150 years) followed by gregarious monocarpy. Relatively, little is known about their pollination and breeding systems. We studied these characteristics in wild Dendrocalamus membranaceus populations and cultivated Dendrocalamus sinicus populations distributed in the Yunnan Province of China. Floral morphology, flower visitors and breeding system were studied from 2013 to 2015. Both bamboos were protogynous, but flowering periods of florets overlapped providing opportunities for self-pollination amongst florets, especially in D. membranaceus. There was no agamospermy in either species. Seed set of D. sinicus was low (0.42 ± 0.42 %) under natural pollination but higher (8.89 ± 2.55 %) after artificial xenogamy. Seed set of D. membranaceus was higher (7.49 ± 0.82 %) in mass flowering populations and 2.14 ± 0.25 % in sporadically flowering populations. The Asian honeybee Apis cerana could provide cross-pollination of D. membranaceus and D. sinicus, and flower visitation peaked at 1000-1200 h. Pollination limitation due to lack of pollinators or pollen was detected in the cultivated populations of D. sinicus and sporadically flowering populations of D. membranaceus. Pollination limitation was not obvious within mass flowering populations. Hand pollination could significantly increase seed set of these two bamboo species. Dendrocalamus membranaceus and D. sinicus were self-compatible and have a mixed-mating system with outcrossing being pre-dominant. Their seed production was limited by the quantity of pollen and pollinator activity. Honeybees were observed as effective pollinators.

Morphological differentiation in Asian honey bee (Apis cerana) populations in the basin and highlands of southwestern China

In the evolutionary process, honey bee populations became divergent due to geographical barriers or ecological adaptation, but to date which specific barriers and ecological isolation conditions that blocked the honey bee gene flow remain uncertain. Here, the morphometric divergence of Apis cerana was studied across southwestern China, a region of diverse topography, featuring a low-elevation basin in the east and a high-elevation mountain and plateau in the west. A multivariate morphometric analysis was conducted on 1482 A. cerana individuals from 25 sampling sites across Sichuan province. The populations dwelling in high-elevation areas with larger body sizes and darker coloration were differentiated from the eastern low-elevation basin population. Moreover, the populations dwelling in the Jinshajiang, Yalongjiang, and DaduRiver Valleys showed significant divergence. Our data indicate that the morphometric variation between the high and low altitudes, probably due to the adaptation to the integrated effects of ecological factors such as air temperature, humidity, the nectar and pollen plants, and light intensity etc. Additionally, the mountains with an altitude of more than 3300 m and a honey bee-free zone probably served as a barrier to gene flow between the river valley populations.