First large-scale study reveals important losses of managed honey bee and stingless bee colonies in Latin America

Over the last quarter century, increasing honey bee colony losses motivated standardized large-scale surveys of managed honey bees (Apis mellifera), particularly in Europe and the United States. Here we present the first large-scale standardized survey of colony losses of managed honey bees and stingless bees across Latin America. Overall, 1736 beekeepers and 165 meliponiculturists participated in the 2-year survey (2016-2017 and 2017-2018). On average, 30.4% of honey bee colonies and 39.6% of stingless bee colonies were lost per year across the region. Summer losses were higher than winter losses in stingless bees (30.9% and 22.2%, respectively) but not in honey bees (18.8% and 20.6%, respectively). Colony loss increased with operation size during the summer in both honey bees and stingless bees and decreased with operation size during the winter in stingless bees. Furthermore, losses differed significantly between countries and across years for both beekeepers and meliponiculturists. Overall, winter losses of honey bee colonies in Latin America (20.6%) position this region between Europe (12.5%) and the United States (40.4%). These results highlight the magnitude of bee colony losses occurring in the region and suggest difficulties in maintaining overall colony health and economic survival for beekeepers and meliponiculturists.

The role of temperature on the development of circadian rhythms in honey bee workers

Circadian rhythms in honey bees are involved in various processes that impact colony survival. For example, young nurses take care of the brood constantly throughout the day and lack circadian rhythms. At the same time, foragers use the circadian clock to remember and predict food availability in subsequent days. Previous studies exploring the ontogeny of circadian rhythms of workers showed that the onset of rhythms is faster in the colony environment (~2 days) than if workers were immediately isolated after eclosion (7-9 days). However, which specific environmental factors influenced the early development of worker circadian rhythms remained unknown. We hypothesized that brood nest temperature plays a key role in the development of circadian rhythmicity in young workers. Our results show that young workers kept at brood nest-like temperatures (33-35 °C) in the laboratory develop circadian rhythms faster and in greater proportion than bees kept at lower temperatures (24-26 °C). In addition, we examined if the effect of colony temperature during the first 48 h after emergence is sufficient to increase the rate and proportion of development of circadian rhythmicity. We observed that twice as many individuals exposed to 35 °C during the first 48 h developed circadian rhythms compared to individuals kept at 25 °C, suggesting a critical developmental period where brood nest temperatures are important for the development of the circadian system. Together, our findings show that temperature, which is socially regulated inside the hive, is a key factor that influences the ontogeny of circadian rhythmicity of workers.

Effects of lithium on locomotor activity and circadian rhythm of honey bees

Lithium has been considered a potential acaricidal agent against the honey bee (Apis mellifera) parasite Varroa. It is known that lithium suppresses elevated activity and regulates circadian rhythms and light response when administered to humans as a primary therapeutic chemical for bipolar disorder and to other bipolar syndrome model organisms, given the crucial role of timing in the bee's foraging activity and the alternating sunlight vs dark colony environment bees are exposed, we explored the influence of lithium on locomotor activity (LMA) and circadian rhythm of honey bees. We conducted acute and chronic lithium administration experiments, altering light conditions and lithium doses to assess LMA and circadian rhythm changes. We fed bees one time 10 μl sucrose solution with 0, 50, 150, and 450 mM LiCl in the acute application experiment and 0, 1, 5, and 10 mmol/kg LiCl ad libitum in bee candy in the chronic application experiment. Both acute and chronic lithium treatments significantly decreased the induced LMA under constant light. Chronic lithium treatment disrupted circadian rhythmicity in constant darkness. The circadian period was lengthened by lithium treatment under constant light. We discuss the results in the context of Varroa control and lithium's effect on bipolar disorder.

Gut microbiota variation of a tropical oil-collecting bee species far exceeds that of the honeybee

Introduction

Interest for bee microbiota has recently been rising, alleviating the gap in knowledge in regard to drivers of solitary bee gut microbiota. However, no study has addressed the microbial acquisition routes of tropical solitary bees. For both social and solitary bees, the gut microbiota has several essential roles such as food processing and immune responses. While social bees such as honeybees maintain a constant gut microbiota by direct transmission from individuals of the same hive, solitary bees do not have direct contact between generations. They thus acquire their gut microbiota from the environment and/or the provision of their brood cell. To establish the role of life history in structuring the gut microbiota of solitary bees, we characterized the gut microbiota of Centris decolorata from a beach population in Mayagüez, Puerto Rico. Females provide the initial brood cell provision for the larvae, while males patrol the nest without any contact with it. We hypothesized that this behavior influences their gut microbiota, and that the origin of larval microbiota is from brood cell provisions.

Methods

We collected samples from adult females and males of C. decolorata (n = 10 each, n = 20), larvae (n = 4), and brood cell provisions (n = 10). For comparison purposes, we also sampled co-occurring female foragers of social Apis mellifera (n = 6). The samples were dissected, their DNA extracted, and gut microbiota sequenced using 16S rRNA genes. Pollen loads of A. mellifera and C. decolorata were analyzed and interactions between bee species and their plant resources were visualized using a pollination network.

Results

While we found the gut of A. mellifera contained the same phylotypes previously reported in the literature, we noted that the variability in the gut microbiota of solitary C. decolorata was significantly higher than that of social A. mellifera. Furthermore, the microbiota of adult C. decolorata mostly consisted of acetic acid bacteria whereas that of A. mellifera mostly had lactic acid bacteria. Among C. decolorata, we found significant differences in alpha and beta diversity between adults and their brood cell provisions (Shannon and Chao1 p < 0.05), due to the higher abundance of families such as Rhizobiaceae and Chitinophagaceae in the brood cells, and of Acetobacteraceae in adults. In addition, the pollination network analysis indicated that A. mellifera had a stronger interaction with Byrsonima sp. and a weaker interaction with Combretaceae while interactions between C. decolorata and its plant resources were constant with the null model.

Conclusion

Our data are consistent with the hypothesis that behavioral differences in brood provisioning between solitary and social bees is a factor leading to relatively high variation in the microbiota of the solitary bee.

The Movement of Western Honey Bees (Apis mellifera L.) Among United States and Territories: History, Benefits, Risks, and Mitigation Strategies

Beekeeping is a cornerstone activity that has led to the human-mediated, global spread of western honey bees (Apis mellifera L.) outside their native range of Europe, western Asia, and Africa. The exportation/importation of honey bees (i.e., transfer of honey bees or germplasm between countries) is regulated at the national level in many countries. Honey bees were first imported into the United States in the early 1600’s. Today, honey bee movement (i.e., transport of honey bees among states and territories) is regulated within the United States at the state, territory, and federal levels. At the federal level, honey bees present in the country (in any state or territory) can be moved among states and territories without federal restriction, with the exception of movement to Hawaii. In contrast, regulations at the state and territory levels vary substantially, ranging from no additional regulations beyond those stipulated at the federal level, to strict regulations for the introduction of live colonies, packaged bees, or queens. This variability can lead to inconsistencies in the application of regulations regarding the movement of honey bees among states and territories. In November 2020, we convened a technical working group (TWG), composed of academic and USDA personnel, to review and summarize the (1) history of honey bee importation into/movement within the United States, (2) current regulations regarding honey bee movement and case studies on the application of those regulations, (3) benefits associated with moving honey bees within the United States, (4) risks associated with moving honey bees within the United States, and (5) risk mitigation strategies. This review will be helpful for developing standardized best practices for the safe movement of honey bees between the 48 contiguous states and other states/territories within the United States.

Antibiotics Alter the Expression of Genes Related to Behavioral Development in Honey Bees (Hymenoptera: Apidae)

Honey bees, as many species of social insects, display a division of labor among colony members based on behavioral specializations related to age. Adult worker honey bees perform a series of tasks in the hive when they are young (such as brood care or nursing) and at ca. 2-3 wk of age, shift to foraging for nectar and pollen outside the hive. The transition to foraging involves changes in metabolism and neuroendocrine activities. These changes are associated with a suite of developmental genes. It was recently demonstrated that antibiotics influence behavioral development by accelerating or delaying the onset of foraging depending on timing of antibiotic exposure. To understand the mechanisms of these changes, we conducted a study on the effects of antibiotics on expression of candidate genes known to regulate behavioral development. We demonstrate a delay in the typical changes in gene expression over the lifetime of the individuals that were exposed to antibiotics during immature stage and adulthood. Additionally, we show an acceleration in the typical changes in gene expression on individuals that were expose to antibiotics only during immature stage. These results show that timing of antibiotic exposure alter the typical regulation of behavioral development by metabolic and neuroendocrine processes.

Automated Video Monitoring of Unmarked and Marked Honey Bees at the Hive Entrance

We present a novel system for the automatic video monitoring of honey bee foraging activity at the hive entrance. This monitoring system is built upon convolutional neural networks that perform multiple animal pose estimation without the need for marking. This precise detection of honey bee body parts is a key element of the system to provide detection of entrance and exit events at the entrance of the hive including accurate pollen detection. A detailed evaluation of the quality of the detection and a study of the effect of the parameters are presented. The complete system also integrates identification of barcode marked bees, which enables the monitoring at both aggregate and individual levels. The results obtained on multiple days of video recordings show the applicability of the approach for large-scale deployment. This is an important step forward for the understanding of complex behaviors exhibited by honey bees and the automatic assessment of colony health.

Tissue-specific transcriptional patterns underlie seasonal phenotypes in honey bees (Apis mellifera)

Faced with adverse conditions, such as winter in temperate regions or hot and dry conditions in tropical regions, many insect species enter a state of diapause, a period of dormancy associated with a reduction or arrest of physical activity, development and reproduction. Changes in common physiological pathways underlie diapause phenotypes in different insect species. However, most transcriptomic studies of diapause have not simultaneously evaluated and compared expression patterns in different tissues. Honey bees (Apis mellifera) represent a unique model system to study the mechanisms underpinning diapause-related phenotypes. In winter, honey bees exhibit a classic diapause phenotype, with reduced metabolic activity, increased physiological nutritional resources and altered hormonal profiles. However, winter bees actively heat their colony by vibrating their wing muscles; thus, this tissue is not quiescent. Here, we evaluated the transcriptional profiles of flight muscle tissue and fat body tissue (involved in nutrient storage, metabolism and immune function) of winter bees. We also evaluated two behavioural phenotypes of summer bees: nurses, which exhibit high nutritional stores and low flight activity, and foragers, which exhibit low nutritional stores and high flight activity. We found winter bees and nurses have similar fat body transcriptional profiles, whereas winter bees and foragers have similar flight muscle transcriptional profiles. Additionally, differentially expressed genes were enriched in diapause-related gene ontology terms. Thus, honey bees exhibit tissue-specific transcriptional profiles associated with seasonal phenotypes, laying the groundwork for future studies evaluating the mechanisms, evolution and consequences of this tissue-specific regulation.

Parallel mechanisms of visual memory formation across distinct regions of the honey bee brain

Visual learning is vital to the behavioral ecology of the Western honey bee (Apis mellifera). Honey bee workers forage for floral resources, a behavior that requires the learning and long-term memory of visual landmarks, but how these memories are mapped to the brain remains poorly understood. To address this gap in our understanding, we collected bees that successfully learned visual associations in a conditioned aversion paradigm and compared gene expression correlates of memory formation in the mushroom bodies, a higher-order sensory integration center classically thought to contribute to learning, as well as the optic lobes, the primary visual neuropil responsible for sensory transduction of visual information. We quantified expression of CREB and CaMKII, two classical genetic markers of learning, and fen-1, a gene specifically associated with punishment learning in vertebrates. As expected, we found substantial involvement of the mushroom bodies for all three markers but additionally report the involvement of the optic lobes across a similar time course. Our findings imply the molecular involvement of a sensory neuropil during visual associative learning parallel to a higher-order brain region, furthering our understanding of how a tiny brain processes environmental signals.

The Role of Colony Temperature in the Entrainment of Circadian Rhythms of Honey Bee Foragers

Honey bees utilize their circadian rhythms to accurately predict the time of day. This ability allows foragers to remember the specific timing of food availability and its location for several days. Previous studies have provided strong evidence toward light/dark cycles being the primary Zeitgeber for honey bees. Work in our laboratory described large individual variation in the endogenous period length of honey bee foragers from the same colony and differences in the endogenous rhythms under different constant temperatures. In this study, we further this work by examining the temperature inside the honey bee colony. By placing temperature and light data loggers at different locations inside the colony we measured temperature at various locations within the colony. We observed significant oscillations of the temperature inside the hive, that show seasonal patterns. We then simulated the observed temperature oscillations in the laboratory and found that using the temperature cycle as a Zeitgeber, foragers present large individual differences in the phase of locomotor rhythms for temperature. Moreover, foragers successfully synchronize their locomotor rhythms to these simulated temperature cycles. Advancing the cycle by six hours, resulting in changes in the phase of activity in some foragers in the assay. The results are shown in this study highlight the importance of temperature as a potential Zeitgeber in the field. Future studies will examine the possible functional and evolutionary role of the observed phase differences of circadian rhythms.

Antibiotics in hives and their effects on honey bee physiology and behavioral development

Recurrent honeybee losses make it critical to understand the impact of human interventions, such as antibiotic use in apiculture. Antibiotics are used to prevent or treat bacterial infections in colonies. However, little is known about their effects on honeybee development. We studied the effect of two commercial beekeeping antibiotics on the bee physiology and behavior throughout development. Our results show that antibiotic treatments have an effect on amount of lipids and rate of behavioral development. Lipid amount in treated bees was higher than those not treated. Also, the timing of antibiotic treatment had distinct effects for the age of onset of behaviors, starting with cleaning, then nursing and lastly foraging. Bees treated during larva-pupa stages demonstrated an accelerated behavioral development and loss of lipids, while bees treated from larva to adulthood had a delay in behavioral development and loss of lipids. The effects were shared across the two antibiotics tested, TerramycinR (oxytetracycline) and TylanR (tylosin tartrate). These effects of antibiotic treatments suggest a role of microbiota in the interaction between the fat body and brain that is important for honeybee behavioral development.This paper has an associated First Person interview with the first author of the article.

Soybean aphid biotype 1 genome: Insights into the invasive biology and adaptive evolution of a major agricultural pest

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) is a serious pest of the soybean plant, Glycine max, a major world-wide agricultural crop. We assembled a de novo genome sequence of Ap. glycines Biotype 1, from a culture established shortly after this species invaded North America. 20.4% of the Ap. glycines proteome is duplicated. These in-paralogs are enriched with Gene Ontology (GO) categories mostly related to apoptosis, a possible adaptation to plant chemistry and other environmental stressors. Approximately one-third of these genes show parallel duplication in other aphids. But Ap. gossypii, its closest related species, has the lowest number of these duplicated genes. An Illumina GoldenGate assay of 2380 SNPs was used to determine the world-wide population structure of Ap. Glycines. China and South Korean aphids are the closest to those in North America. China is the likely origin of other Asian aphid populations. The most distantly related aphids to those in North America are from Australia. The diversity of Ap. glycines in North America has decreased over time since its arrival. The genetic diversity of Ap. glycines North American population sampled shortly after its first detection in 2001 up to 2012 does not appear to correlate with geography. However, aphids collected on soybean Rag experimental varieties in Minnesota (MN), Iowa (IA), and Wisconsin (WI), closer to high density Rhamnus cathartica stands, appear to have higher capacity to colonize resistant soybean plants than aphids sampled in Ohio (OH), North Dakota (ND), and South Dakota (SD). Samples from the former states have SNP alleles with high F_ST values and frequencies, that overlap with genes involved in iron metabolism, a crucial metabolic pathway that may be affected by the Rag-associated soybean plant response. The Ap. glycines Biotype 1 genome will provide needed information for future analyses of mechanisms of aphid virulence and pesticide resistance as well as facilitate comparative analyses between aphids with differing natural history and host plant range.

Colonization history and population differentiation of the Honey Bees (Apis mellifera L.) in Puerto Rico

Honey bees (Apis mellifera L.) are the primary commercial pollinators across the world. The subspecies A. m. scutellata originated in Africa and was introduced to the Americas in 1956. For the last 60 years, it hybridized successfully with European subspecies, previous residents in the area. The result of this hybridization was called Africanized honey bee (AHB). AHB has spread since then, arriving to Puerto Rico (PR) in 1994. The honey bee population on the island acquired a mosaic of features from AHB or the European honey bee (EHB). AHB in Puerto Rico shows a major distinctive characteristic, docile behavior, and is called gentle Africanized honey bees (gAHB). We used 917 SNPs to examine the population structure, genetic differentiation, origin, and history of range expansion and colonization of gAHB in PR. We compared gAHB to populations that span the current distribution of A. mellifera worldwide. The gAHB population is shown to be a single population that differs genetically from the examined populations of AHB. Texas and PR groups are the closest genetically. Our results support the hypothesis that the Texas AHB population is the source of gAHB in Puerto Rico.

Appetitive reversal learning differences of two honey bee subspecies with different foraging behaviors

We aimed to examine mechanistically the observed foraging differences across two honey bee, Apis mellifera, subspecies using the proboscis extension response assay. Specifically, we compared differences in appetitive reversal learning ability between honey bee subspecies: Apis mellifera caucasica (Pollman), and Apis mellifera syriaca (Skorikov) in a "common garden" apiary. It was hypothesized that specific learning differences could explain previously observed foraging behavior differences of these subspecies: A.m. caucasica switches between different flower color morphs in response to reward variability, and A.m. syriaca does not switch. We suggest that flower constancy allows reduced exposure by minimizing search and handling time, whereas plasticity is important when maximizing harvest in preparation for long winter is at a premium. In the initial or Acquisition phase of the test we examined specifically discrimination learning, where bees were trained to respond to a paired conditioned stimulus with an unconditioned stimulus and not to respond to a second conditioned stimulus that is not followed by an unconditioned stimulus. We found no significant differences among the subspecies in the Acquisition phase in appetitive learning. During the second, Reversal phase of the experiment, where flexibility in association was tested, the paired and unpaired conditioned stimuli were reversed. During the Reversal phase A.m. syriaca showed a reduced ability to learn the reverse association in the appetitive learning task. This observation is consistent with the hypothesis that A.m. syriaca foragers cannot change the foraging choice because of lack of flexibility in appetitive associations under changing contingencies. Interestingly, both subspecies continued responding to the previously rewarded conditioned stimulus in the reversal phase. We discuss potential ecological correlates and molecular underpinnings of these differences in learning across the two subspecies. In addition, in a supplemental experiment we demonstrated that these differences in appetitive reversal learning do not occur in other learning contexts.

A soft selective sweep during rapid evolution of gentle behaviour in an Africanized honeybee

Highly aggressive Africanized honeybees (AHB) invaded Puerto Rico (PR) in 1994, displacing gentle European honeybees (EHB) in many locations. Gentle AHB (gAHB), unknown anywhere else in the world, subsequently evolved on the island within a few generations. Here we sequence whole genomes from gAHB and EHB populations, as well as a North American AHB population, a likely source of the founder AHB on PR. We show that gAHB retains high levels of genetic diversity after evolution of gentle behaviour, despite selection on standing variation. We observe multiple genomic loci with significant signatures of selection. Rapid evolution during colonization of novel habitats can generate major changes to characteristics such as morphological or colouration traits, usually controlled by one or more major genetic loci. Here we describe a soft selective sweep, acting at multiple loci across the genome, that occurred during, and may have mediated, the rapid evolution of a behavioural trait.

Africanized honey bees (AHB) are notoriously aggressive, but in Puerto Rico they have a ‘gentle’ phenotype. Here, Avalos et al. show that there has been a soft selective sweep at several loci in the Puerto Rican AHB population and suggest a role in the rapid evolution of gentle behaviour.

Social signals and aversive learning in honey bee drones and workers

The dissemination of information is a basic element of group cohesion. In honey bees (Apis mellifera Linnaeus 1758), like in other social insects, the principal method for colony-wide information exchange is communication via pheromones. This medium of communication allows multiple individuals to conduct tasks critical to colony survival. Social signaling also establishes conflict at the level of the individual who must trade-off between attending to the immediate environment or the social demand. In this study we examined this conflict by challenging highly social worker honey bees, and less social male drone honey bees undergoing aversive training by presenting them with a social stress signal (isopentyl acetate, IPA). We utilized IPA exposure methods that caused lower learning performance in appetitive learning in workers. Exposure to isopentyl acetate (IPA) did not affect performance of drones and had a dose-specific effect on worker response, with positive effects diminishing at higher IPA doses. The IPA effects are specific because non-social cues, such as the odor cineole, improve learning performance in drones, and social homing signals (geraniol) did not have a discernible effect on drone or worker performance. We conclude that social signals do generate conflict and that response to them is dependent on signal relevance to the individual as well as the context. We discuss the effect of social signal on learning both related to its social role and potential evolutionary history.

A Landscape Analysis to Understand Orientation of Honey Bee (Hymenoptera: Apidae) Drones in Puerto Rico

Honey bees [Apis mellifera L. (Apidae, Hymenoptera)] show spatial learning behavior or orientation, in which animals make use of structured home ranges for their daily activities. Worker (female) orientation has been studied more extensively than drone (male) orientation. Given the extensive and large flight range of drones as part of their reproductive biology, the study of drone orientation may provide new insight on landscape features important for orientation. We report the return rate and orientation of drones released at three distances (1, 2, and 4 km) and at the four cardinal points from an apiary located in Gurabo, Puerto Rico. We used high-resolution aerial photographs to describe landscape characteristics at the releasing sites and at the apiary. Analyses of variance were used to test significance among returning times from different distances and directions. A principal components analysis was used to describe the landscape at the releasing sites and generalized linear models were used to identify landscape characteristics that influenced the returning times of drones. Our results showed for the first time that drones are able to return from as far as 4 km from the colony. Distance to drone congregation area, orientation, and tree lines were the most important landscape characteristics influencing drone return rate. We discuss the role of landscape in drone orientation.

Relative frequency of norovirus infection in children with acute gastroenteritis

AIM

The aim of this study was to determine the prevalence of norovirus among children with acute gastroenteritis in 2009 and 2010. We also aimed that, to detecting the possible clinical and laboratory differences among cases in 2009 and 2010.

METHODS

Fecal samples were collected from children under 16 years of age who were admitted for acute gastroenteritis. Norovirus was detected using immunochromatography. For the comparison of seasonal distribution, clinical manifestations, and laboratory results between cases, we divided subjects into two groups by year.

RESULTS

Norovirus infection was detected in 112 of the 1027 collected samples (10.9%). In three cases with norovirus, other enteric viruses like rotavirus and adenovirus are detected concurrently, and these were excluded. After the exclusion of three cases with co-infections, statistical analysis was made in 109 cases. Most of the positive cases were between 1-24 months of age (N.=75, 67%). The rate of norovirus infection peaked in winter in 2010 (P<0.05). However, the rates were not significantly different between seasons in 2009 (P>0.05). We did not detect any positive cases in late summer and autumn in 2010. Diarrhea (97.2%), vomiting (95.4%), and abdominal pain (65.1%) were most frequently encountered symptoms of patients with norovirus. Leukocytosis and neutrophilia were significantly higher in 2010 than 2009 (P<0.05).

CONCLUSION

The prevalence and clinical characteristics of norovirus in our study group is similar but seasonal distribution is different between two years. Most of the cases were <24 months of age. Like rotavirus, norovirus vaccine can be developed to prevent infection.

Ethanol-induced effects on sting extension response and punishment learning in the western honey bee (Apis mellifera)

Acute ethanol administration is associated with sedation and analgesia as well as behavioral disinhibition and memory loss but the mechanisms underlying these effects remain to be elucidated. During the past decade, insects have emerged as important model systems to understand the neural and genetic bases of alcohol effects. However, novel assays to assess ethanol's effects on complex behaviors in social or isolated contexts are necessary. Here we used the honey bee as an especially relevant model system since bees are typically exposed to ethanol in nature when collecting standing nectar crop of flowers, and there is recent evidence for independent biological significance of this exposure for social behavior. Bee's inhibitory control of the sting extension response (SER) and a conditioned-place aversion assay were used to study ethanol effects on analgesia, behavioral disinhibition, and associative learning. Our findings indicate that although ethanol, in a dose-dependent manner, increases SER thresholds (analgesic effects), it disrupts the ability of honey bees to inhibit SER and to associate aversive stimuli with their environment. These results suggest that ethanol's effects on analgesia, behavioral disinhibition and associative learning are common across vertebrates and invertebrates. These results add to the use of honey bees as an ethanol model to understand ethanol's effects on complex, socially relevant behaviors.

Aversive conditioning in honey bees (Apis mellifera anatolica): a comparison of drones and workers

Honey bees provide a model system to elucidate the relationship between sociality and complex behaviors within the same species, as females (workers) are highly social and males (drones) are more solitary. We report on aversive learning studies in drone and worker honey bees (Apis mellifera anatolica) in escape, punishment and discriminative punishment situations. In all three experiments, a newly developed electric shock avoidance assay was used. The comparisons of expected and observed responses were performed with conventional statistical methods and a systematic randomization modeling approach called object oriented modeling. The escape experiment consisted of two measurements recorded in a master-yoked paradigm: frequency of response and latency to respond following administration of shock. Master individuals could terminate an unavoidable shock triggered by a decrementing 30 s timer by crossing the shuttlebox centerline following shock activation. Across all groups, there was large individual response variation. When assessing group response frequency and latency, master subjects performed better than yoked subjects for both workers and drones. In the punishment experiment, individuals were shocked upon entering the shock portion of a bilaterally wired shuttlebox. The shock portion was spatially static and unsignalled. Only workers effectively avoided the shock. The discriminative punishment experiment repeated the punishment experiment but included a counterbalanced blue and yellow background signal and the side of shock was manipulated. Drones correctly responded less than workers when shock was paired with blue. However, when shock was paired with yellow there was no observable difference between drones and workers.

Measuring individual locomotor rhythms in honey bees, paper wasps and other similar-sized insects

Circadian rhythms in social insects are highly plastic and are modulated by multiple factors. In addition, complex behaviors such as sun-compass orientation and time learning are clearly regulated by the circadian system in these organisms. Despite these unique features of social insect clocks, the mechanisms as well as the functional and evolutionary relevance of these traits remain largely unknown. Here we show a modification of the Drosophila activity monitoring (DAM) system that allowed us to measure locomotor rhythms of the honey bee, Apis mellifera (three variants; gAHB, carnica and caucasica), and two paper wasps (Polistes crinitus and Mischocyttarus phthisicus). A side-by-side comparison of the endogenous period under constant darkness (free-running period) led us to the realization that these social insects exhibit significant deviations from the Earth's 24 h rotational period as well as a large degree of inter-individual variation compared with Drosophila. Experiments at different temperatures, using honey bees as a model, revealed that testing the endogenous rhythm at 35°C, which is the hive's core temperature, results in average periods closer to 24 h compared with 25°C (23.8 h at 35°C versus 22.7 h at 25°C). This finding suggests that the degree of tuning of circadian temperature compensation varies among different organisms. We expect that the commercial availability, cost-effectiveness and integrated nature of this monitoring system will facilitate the growth of the circadian field in these social insects and catalyze our understanding of the mechanisms as well as the functional and evolutionary relevance of circadian rhythms.

Genetic structure of the gentle Africanized honey bee population (gAHB) in Puerto Rico

BACKGROUND

The Africanized honey bee is one of the most spectacular invasions in the Americas. African bees escaped from apiaries in Brazil in 1956, spread over Americas and by 1994 they were reported in Puerto Rico. In contrast to other places, the oceanic island conditions in Puerto Rico may mean a single introduction and different dynamics of the resident European and new-coming Africanized bees.To examine the genetic variation of honey bee feral populations and colonies from different locations in Puerto Rico, we used eight known polymorphic microsatellite loci.

RESULTS

In Puerto Rico, gAHB population does not show any genetic structure (Fst = 0.0783), and is best described as one honey bee population, product of hybridization of AHB and EHB. The genetic variability in this Africanized population was similar to that reported in studies from Texas. We observed that European private allele frequencies are high in all but one locus. This contrasts with mainland Africanized populations, where European allele frequencies are diminished. Two loci with European private alleles, one on Linkage Group 7, known to carry two known defensiveness Quantitative Trait Loci (QTLs), and the other on Linkage Group 1, known to carry three functionally studied genes and 11 candidate genes associated with Varroa resistance mechanisms were respectively, significantly greater or lower in European allele frequency than the other loci with European private alleles.

CONCLUSIONS

Genetic structure of Puerto Rico gAHB differs from mainland AHB populations, probably representing evolutionary processes on the island.

A Tool for Every Job: Assessing the Need for a Universal Definition of Tool Use

Once considered only a human behavior, reports of tool use by a variety of animals have accumulated. Likewise, various definitions of tool use have also amassed. Although some researchers argue that understanding the evolutionary drivers of tool use is more important than identifying and describing these behaviors, the central issue of defining what constitutes tool use has not been fully addressed. Here we analyze prominent definitions of tool use and review the application of these definitions in scientific and educational literature. We demonstrate that many behaviors recently described as tool use do not meet criteria for prevalent definitions, while other neglected behaviors may constitute a form of tool use. These examples show how the use of inconsistent definitions of tool use in research can result in different conclusions from the same observations. Our aim is to demonstrate that a universally acceptable definition of tool use based on traditional, evolutionary, and operational understanding of behavior is needed. The rationale is that this review will stimulate the consistent and explicit use of specific terminology in tool use research. This would help define specific examples of each natural observation from a common measuring stick, allowing better comparative studies and classification of these unique behaviors.//

Gentle Africanized bees on an oceanic island

Oceanic islands have reduced resources and natural enemies and potentially affect life history traits of arriving organisms. Among the most spectacular invasions in the Western hemisphere is that of the Africanized honeybee. We hypothesized that in the oceanic island Puerto Rico, Africanized bees will exhibit differences from the mainland population such as for defensiveness and other linked traits. We evaluated the extent of Africanization through three typical Africanized traits: wing size, defensive behavior, and resistance to Varroa destructor mites. All sampled colonies were Africanized by maternal descent, with over 65% presence of European alleles at the S-3 nuclear locus. In two assays evaluating defense, Puerto Rican bees showed low defensiveness similar to European bees. In morphology and resistance to mites, Africanized bees from Puerto Rico are similar to other Africanized bees. In behavioral assays on mechanisms of resistance to Varroa, we directly observed that Puerto Rican Africanized bees groomed-off and bit the mites as been observed in other studies. In no other location, Africanized bees have reduced defensiveness while retaining typical traits such as wing size and mite resistance. This mosaic of traits that has resulted during the invasion of an oceanic island has implications for behavior, evolution, and agriculture.

Landscape analysis of drone congregation areas of the honey bee, Apis mellifera

Male honey bees fly and gather at Drone Congregation Areas (DCAs), where drones and queens mate in flight. DCAs occur in places with presumably characteristic features. Using previously described landscape characteristics and observations on flight direction of drones in nearby apiaries, 36 candidate locations were chosen across the main island of Puerto Rico. At these locations, the presence or absence of DCAs was tested by lifting a helium balloon equipped with queen-sex-pheromone-impregnated bait, and visually determining the presence of high numbers of drones. Because of the wide distribution of honey bees in Puerto Rico, it was expected that most of the potential DCAs would be used as such by drones and queens from nearby colonies. Eight DCAs were found in the 36 candidate locations. Locations with and without DCAs were compared in a landscape analysis including characteristics that were described to be associated with DCAs and others. Aspect (direction of slope) and density of trails were found to be significantly associated with the presence of DCAs.

Dopamine and octopamine influence avoidance learning of honey bees in a place preference assay

Biogenic amines are widely characterized in pathways evaluating reward and punishment, resulting in appropriate aversive or appetitive responses of vertebrates and invertebrates. We utilized the honey bee model and a newly developed spatial avoidance conditioning assay to probe effects of biogenic amines octopamine (OA) and dopamine (DA) on avoidance learning. In this new protocol non-harnessed bees associate a spatial color cue with mild electric shock punishment. After a number of experiences with color and shock the bees no longer enter the compartment associated with punishment. Intrinsic aspects of avoidance conditioning are associated with natural behavior of bees such as punishment (lack of food, explosive pollination mechanisms, danger of predation, heat, etc.) and their association to floral traits or other spatial cues during foraging. The results show that DA reduces the punishment received whereas octopamine OA increases the punishment received. These effects are dose-dependent and specific to the acquisition phase of training. The effects during acquisition are specific as shown in experiments using the antagonists Pimozide and Mianserin for DA and OA receptors, respectively. This study demonstrates the integrative role of biogenic amines in aversive learning in the honey bee as modeled in a novel non-appetitive avoidance learning assay.

Proboscis conditioning experiments with honeybees, Apis mellifera caucasica, with butyric acid and DEET mixture as conditioned and unconditioned stimuli

Three experiments are described investigating whether olfactory repellents DEET and butyric acid can support the classical conditioning of proboscis extension in the honeybee, Apis mellifera caucasica (Hymenoptera: Apidae). In the first experiment DEET and butyric acid readily led to standard acquisition and extinction effects, which are comparable to the use of cinnamon as a conditioned stimulus. These results demonstrate that the odor of DEET or butyric acid is not intrinsically repellent to honey bees. In a second experiment, with DEET and butyric acid mixed with sucrose as an unconditioned stimulus, proboscis conditioning was not established. After several trials, few animals responded to the unconditioned stimulus. These results demonstrate that these chemicals are gustatory repellents when in direct contact. In the last experiment a conditioned suppression paradigm was used. Exposing animals to butyric acid or DEET when the proboscis was extended by direct sucrose stimulation or by learning revealed that retraction of the proboscis was similar to another novel odor, lavender, and in all cases greatest when the animal was not permitted to feed. These results again demonstrate that DEET or butyric acid are not olfactory repellents, and in addition, conditioned suppression is influenced by feeding state of the bee.

Octopamine influences honey bee foraging preference

Colony condition and differences in individual preferences influence forage type collected by bees. Physiological bases for the changing preferences of individual foragers are just beginning to be examined. Recently, for honey bees octopamine is shown to influence age at onset of foraging and probability of dance for rewards. However, octopamine has not been causally linked with foraging preference in the field. We tested the hypothesis that changes in octopamine may alter forage type (preference hypothesis). We treated identified foragers orally with octopamine or its immediate precursor, tyramine, or sucrose syrup (control). Octopamine-treated foragers switched type of material collected; control bees did not. Tyramine group results were not different from the control group. In addition, sugar concentrations of nectar collected by foragers after octopamine treatment were lower than before treatment, indicating change in preference. In contrast, before and after nectar concentrations for bees in the control group were similar. These results, taken together, support the preference hypothesis.

Juvenile hormone, reproduction, and worker behavior in the neotropical social wasp Polistes canadensis

Previous studies of the division of labor in colonies of eusocial Hymenoptera (wasps and bees) have led to two hypotheses regarding the evolution of juvenile hormone (JH) involvement. The novel- or single-function hypothesis proposes that the role of JH has changed from an exclusively reproductive function in primitively eusocial species (those lacking morphologically distinct queen and worker castes), to an exclusively behavioral function in highly eusocial societies (those containing morphologically distinct castes). In contrast, the split-function hypothesis proposes that JH originally functioned in the regulation of both reproduction and behavior in ancestral solitary species. Then, when reproductive and brood-care tasks came to be divided between queens and workers, the effects of JH were divided as well, with JH involved in regulation of reproductive maturation of egg-laying queens, and behavioral maturation, manifested as age-correlated changes in worker tasks, of workers. We report experiments designed to test these hypotheses. After documenting age-correlated changes in worker behavior (age polyethism) in the neotropical primitively eusocial wasp Polistes canadensis, we demonstrate that experimental application of the JH analog methoprene accelerates the onset of guarding behavior, an age-correlated task, and increases the number of foraging females; and we demonstrate that JH titers correlate with both ovarian development of queens and task differentiation in workers, as predicted by the split-function hypothesis. These findings support a view of social insect evolution that sees the contrasting worker and queen phenotypes as derived via decoupling of reproductive and brood-care components of the ancestral solitary reproductive physiology.

Physiological bases of genetic differences in cannibalism behavior of the confused flour beetle Tribolium confusum

Physiological causes of genetic differences in cannibalism were examined to gain a better understanding of constraints on behavior evolution. Cannibalism has complex population level consequences in Tribolium confusum, including dramatic effects on population size. Laboratory strains with low and high cannibalism rates, obtained through inbreeding, have maintained distinct levels of cannibalism for over two decades even in the absence of artificial selection to maintain the differences. Why strains differ in their cannibalism rates was examined by measuring: (1) the nutritional benefit from cannibalism in both nutritionally good and poor environments, and (2) the possibility that eggs are an important source of water. How strains achieve differences in cannibalism was examined by testing for differences between strains in their ability to find eggs and in their tendency to eat eggs. Beetles from both strains survive equally well in a nutritionally good environment, but they accomplish this in different ways. The low cannibalism strain has high survivorship with and without cannibalism. The high cannibalism strain has low survivorship when not fed eggs and survivorship equivalent to the low cannibalism strain when fed eggs, suggesting it compensates for poor nutritional adaptation by eating eggs. The strains also differ in feeding behavior; beetles from the high cannibalism strain have a higher appetite for eggs. Beetles from the two strains did not differ in locomotor activity, search efficiency, or need for water. The observed behavioral and nutritional differences may contribute to the maintenance of different levels of cannibalism.

Expansion of the neuropil of the mushroom bodies in male honey bees is coincident with initiation of flight

The mushroom bodies (MB), the insect brain structures most often associated with learning, have previously been shown to exhibit structural plasticity during the adult behavioral development of female worker and queen honey bees. We now show that comparable morphological changes occur in the brains of male honey bees (drones). The volume of the MB in the brains of drones was estimated from tissue sections using the Cavalieri method. Brains were obtained from six groups of drones that differed in age and flight experience. Circulating levels of juvenile hormone (JH) in these drones were determined by radioimmunoassay (RIA). There was an expansion of the neuropil of the MB that was temporally associated with drone behavioral development, as in female queens and workers. The observed changes in drones were maintained in the presence of low levels of JH, also as in females. These results suggest that expansion of the neuropil of the MB in honey bees is associated with learning the location of the nest, because this learning is the most prominent aspect of behavioral development common to all members (workers, drones, queen) of the honey bee colony.

Common endocrine and genetic mechanisms of behavioral development in male and worker honey bees and the evolution of division of labor

Temporal polyethism is a highly derived form of behavioral development displayed by social insects. Hormonal and genetic mechanisms regulating temporal polyethism in worker honey bees have been identified, but the evolution of these mechanisms is not well understood. We performed three experiments with male honey bees (drones) to investigate how mechanisms regulating temporal polyethism may have evolved because, relative to workers, drones display an intriguing combination of similarities and differences in behavioral development. We report that behavioral development in drones is regulated by mechanisms common to workers. In experiment 1, drones treated with the juvenile hormone (JH) analog methoprene started flying at significantly younger ages than did control drones, as is the case for workers. In experiment 2, there was an age-related increase in JH associated with the onset of drone flight, as in workers. In experiment 3, drones derived from workers with fast rates of behavioral development themselves started flying at younger ages than drones derived from workers with slower rates of behavioral development. These results suggest that endocrine and genetic mechanisms associated with temporal polyethism did not evolve strictly within the context of worker social behavior.

Volume changes in the mushroom bodies of adult honey bee queens

The volume of the mushroom bodies of the brains of honey bee queens (Apis mellifera) was estimated using the method of Cavalieri. Tissue sampled was obtained from queens in five different behavioral and reproductive states: 1-day-old virgin queens, 14-day-old virgin queens, 14-day-old instrumentally inseminated queens, 9- to 13-day old naturally mated queens, and 5-month-old naturally mated queens. There were significant volume changes within the mushroom bodies during the first 2 weeks of adult life. The volume occupied by the somata of the intrinsic neuronal population (Kenyon cells) of the mushroom bodies decreased by approximately 30% and the volume of the neuropil of the mushroom bodies increased between 25 and 50%. These volume changes are strikingly similar to those previously reported to occur for worker honey bees switching from hive activities to foraging (Withers, Fahrbach, & Robinson, 1993). However, in this study they were found even in queens that had no flight experience. In addition, queens exhibiting these volume changes were found to have low blood levels of juvenile hormone, while previous studies have shown that foraging worker honey bees have high hormone levels. These results suggest that some aspect of behavioral development common to both the queen and the worker castes is fundamental to protocerebral volume changes early in adulthood in honey bees. If juvenile hormone regulates this process, results from queens suggest that it may play an organizational role.