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Bee populations are facing numerous stressors globally, including environmental pollution by trace metals and metalloids. Understanding whether bees can detect and avoid these pollutants in their food is pivotal, as avoidance abilities may mitigate their exposure to xenobiotics. While these pollutants are known to induce sublethal effects in bees, such as disrupting physiological mechanisms, their potential impacts on locomotive abilities, fat metabolism, and reproductive physiology remain poorly understood. In this study, utilising workers of the buff-tailed bumble bee and two prevalent trace metals, namely cadmium and copper, we aimed to address these knowledge gaps for field-realistic concentrations. Our findings reveal that workers did not reject field-realistic concentrations of cadmium and copper in sucrose solutions. Moreover, they did not reject lethal concentrations of cadmium, although they rejected lethal concentrations of copper. Additionally, we observed no significant effects of field-realistic concentrations of these metals on the walking and flying activities of workers, nor on their fat metabolism and reproductive physiology. Overall, our results suggest that bumble bees may not avoid cadmium and copper at environmental concentrations, but ingestion of these metals in natural settings may not adversely affect locomotive abilities, fat metabolism, or reproductive physiology. However, given the conservative nature of our study, we still recommend future research to employ higher concentrations over longer durations to mimic conditions in heavily polluted areas (i.e., mine surrounding). Furthermore, investigations should ascertain whether field-realistic concentrations of metals exert no impact on bee larvae. [ABSTRACT FROM AUTHOR]

Simple Summary: This study explores the potential of honeybees to detect and differentiate the odor of invasive red imported fire ants (Solenopsis invicta) using olfactory conditioning. By training bees with deceased ants, the results showed that bees quickly learned to recognize ant odors, with stronger responses to higher odor intensities. Bees generalized well across different worker castes and female alates and could recognize live ants after being conditioned with deceased ones. Discrimination varied by species but improved with a latent inhibition procedure. The findings suggest that honeybees may serve as a valuable tool for S. invicta detection and surveillance. Invasive red imported fire ants (Solenopsis invicta) create a serious threat to public safety, agriculture, biodiversity, and the local economy, necessitating early detection and surveillance, which are currently time-consuming and dependent on the inspector's expertise. This study marks an initial investigation into the potential of honeybees (Apis mellifera) to detect and discriminate the odor of S. invicta through the olfactory conditioning of proboscis extension responses. Deceased S. invicta were used as conditioned stimuli to ensure relevance to non-infested areas. The results showed that the bees rapidly learned to respond to deceased ant odors, with response levels significantly increasing at higher odor intensities. Bees exhibited generalization across the odors of 25 minor workers, 21 median workers, 1 major worker, and 1 female alate. When conditioned with deceased ant odors, bees effectively recognized live ants, particularly when trained on a single minor worker. Discrimination abilities varied by species and were higher when S. invicta was paired with Polyrhachis dives and Nylanderia yaeyamensis, and lower with S. geminata, Pheidole rabo, and Pheidole fervens. Notably, discrimination improved significantly with the application of latent inhibition. These findings suggest that trained honeybees have the potential to detect S. invicta. Further refinement of this approach could enhance its effectiveness for detection and surveillance. [ABSTRACT FROM AUTHOR]

Invasive red imported fire ants (Solenopsis invicta) create a serious threat to public safety, agriculture, biodiversity, and the local economy, necessitating early detection and surveillance, which are currently time-consuming and dependent on the inspector’s expertise. This study marks an initial investigation into the potential of honeybees (Apis mellifera) to detect and discriminate the odor of S. invicta through the olfactory conditioning of proboscis extension responses. Deceased S. invicta were used as conditioned stimuli to ensure relevance to non-infested areas. The results showed that the bees rapidly learned to respond to deceased ant odors, with response levels significantly increasing at higher odor intensities. Bees exhibited generalization across the odors of 25 minor workers, 21 median workers, 1 major worker, and 1 female alate. When conditioned with deceased ant odors, bees effectively recognized live ants, particularly when trained on a single minor worker. Discrimination abilities varied by species and were higher when S. invicta was paired with Polyrhachis dives and Nylanderia yaeyamensis, and lower with S. geminata, Pheidole rabo, and Pheidole fervens. Notably, discrimination improved significantly with the application of latent inhibition. These findings suggest that trained honeybees have the potential to detect S. invicta. Further refinement of this approach could enhance its effectiveness for detection and surveillance.

Stingless bees (Apidae, Meliponini) are a group of highly eusocial bees with pantropic distribution. The variety of life styles among the approximately 600 species and their frequent specialization on a specific habitat type render them a promising group to study how environmental pressures shaped specific traits during evolution. The present review aimed at identifying potential ecological drivers of bee cognition. Some interesting trends emerged from the scarce literature existing on this topic. A species' investment in particular neural substrates (sensory periphery, centers of information processing and integration) is associated with its foraging and anti-predator strategies. Innate preferences are tuned to often very specific needs, including defense against nest robbers, obligatory cleptobiosis, or foraging under dim-light conditions. These sensory biases, however, can be molded through experience and learning. In addition to associations between particular features of a food source and its quality, bees evaluate feeding sites based on previous experience with signals and cues that indicate potential competition. Moreover, inexperienced foragers learn specific characteristics of an exploited resource, like its scent or profitability, through recruitment signals produced by active food collectors. However, the cognitive abilities of bees, which are key to efficient food collection, are threatened by anthropogenic stressors. Sublethal doses of agrochemicals, in particular, have been shown to provoke cell death of higher brain centers, therewith reducing learning skills of the exposed individuals. Important questions for future studies are whether and to what extent different levels of cognitive plasticity found among stingless bees may attenuate the impact of human stressors. [ABSTRACT FROM AUTHOR]

The house fly, Musca domestica, is a cosmopolitan filth fly pest common in agricultural and urban areas where decaying organic matter is available for larval development. Adult M. domestica are nuisances and vectors of disease. When sanitation, screens, and sticky fly strips fail to control house fly populations, insecticide baits are often used. The use of baits can lead to the evolution of resistance, including not only physiological resistance to the toxicant but also behavioural resistance to the phagostimulant and to the toxicant. Here, the non‐nutritive sweeteners neotame and allulose were examined for their suitability as replacement phagostimulants in insecticidal baits for house flies. Suitability was assessed using proboscis extension response (PER) and consumption experiments. Allulose was further examined for insecticidal activity. Dry neotame elicited no PER, and it would not easily go into solution, so it was not examined in solution. Both in dry form and in solution, allulose elicited some PER and consumption, but only half or less of what sucrose or fructose elicited. Flies fed allulose alone had lower survival rates than flies fed sucrose alone. When given both allulose and sucrose, flies survived at similar rates to flies only fed sucrose. Neotame is not recommended as a replacement phagostimulant in bait formulations. Allulose alone is not recommended as a replacement phagostimulant. It remains to be seen whether combining allulose with sucrose as the phagostimulant in baits would result in as much bait consumption as just sucrose. If so, it might be worth testing whether the combination could serve as a rotational phagostimulant to prevent behavioural resistance to sucrose from evolving. [ABSTRACT FROM AUTHOR]

BackgroundSublethal exposure to neonicotinoids, a popular class of agricultural pesticides, can lead to behavioral effects that impact the health of pollinators. Therefore, new compounds, such as flupyradifurone (FPF), have recently been developed as 'safer' alternatives. FPF is an excitotoxic nicotinic acetylcholine receptor agonist, similar to neonicotinoids. Given the novelty of FPF, what data exist are focused mostly on assessing the effect of FPF on pollinator mortality. One important avenue for investigation is the potential effect of FPF on the sensitivity of nectar foragers, such as Apis mellifera, to sucrose concentrations. Neonicotinoids can alter this sucrose responsiveness and disrupt foraging. Compounding this effect, neonicotinoid-containing solutions are preferred by A. mellifera over pure sucrose solutions. We therefore conducted four studies, administering FPF under both acute and chronic conditions, and at field-realistic and higher than field-realistic doses, to assess the influence of FPF exposure on sucrose responsiveness and sucrose solutions with FPF in A. mellifera nectar foragers.ResultsWe found no evidence that FPF exposure under acute or chronic field-realistic conditions significantly altered sucrose responsiveness, and we did not find that bees exposed to FPF consumed more of the solution. However, at the much higher median lethal dose (48 h), among bees that survived, FPF-exposed foragers responded to significantly lower concentrations of sucrose than controls and responded at significantly higher rates to all concentrations of sucrose than controls.ConclusionWe found no evidence that FPF alters the sucrose responsiveness of nectar foragers at field-realistic doses during winter or early spring, but caution and further investigation are warranted, particularly on the effects of FPF in conjunction with other stressors. © 2019 Society of Chemical Industry.

However, the honey bees exhibited a reduction in consuming the sucrose containing not less than 1 ug/mL of CdCl SB 2 sb ; although non-significant, there exists the possibility that sucrose containing more than 1 ug/mL of Cd may affect honey bee sucrose responsiveness that is essential for olfactory learning in honey bees [[38]]. We, therefore, investigated whether honey bees exposed to chronic Cd exhibited altered olfactory learning, and we further compared the patterns of brain gene expression between cadmium-exposed bees and control bees using RNA-seq analysis. Our studies showed that the head weight was significantly lower in cadmium-exposed bees when compared to controls, suggesting chronic Cd exposure may have adverse effects on the total protein content of the mandibular and hypopharyngeal glands in the heads of adult honey bees, thus resulting in a decrease in head weight in Cd-exposed bees. [Extracted from the article]

Malnutrition in vertebrates, including humans, is known to affect brain development. Protein deprivation in the early stages of life dramatically impairs cognitive abilities. In insects, dietary protein deficiency influences several physiological and behavioural traits, but it is unknown how protein to carbohydrate (P:C) ratio simultaneously affects survival and cognitive performance.We used the geometric framework approach to examine the effects of P:C ratio in the diet of newly emerged honey bees on their survival, sucrose sensitivity, and learning and memory by conditioning of the proboscis extension response.The P:C ratio in the diet did not affect sucrose sensitivity, whereas it affected lifespan and cognition differently. While lifespan peaked at P:C ratio of 1:19, learning and short‐term memory peaked at P:C ratios of 1:9 and 1:4. Protein deprivation slightly reduced bee lifespan but highly impaired learning and short‐term memory. On the other hand, an excess of protein dramatically reduced bee lifespan with lesser effects on learning and short‐term memory.Bees were only able to form an early long‐term memory when they had been eating a protein diet (P:C ratio of 1:9) during 24 hr before the test, regardless of the diet eaten previously.Our study shows that nutrition affects honey bee cognitive abilities, but that these effects, unlike in vertebrates, can be quickly reversed with an appropriate diet. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Organisms that can detect parasites may have a greater likelihood of avoiding exposure to them. We would expect hosts that share an evolutionary history with a parasite to be more likely to detect and avoid it compared to novel hosts. Nosema ceranae is a gut parasite of the Asian honey bee, Apis cerana, that has relatively recently been detected in the western honey bee, Apis mellifera. Using a Proboscis Extension Response assay, we found that A. cerana was significantly more likely than A. mellifera to avoid sucrose solutions with concentrations above 1 × 106 N. ceranae spores per mL. However, neither species avoided the sucrose solutions with lower N. ceranae concentrations, similar to those detected on flowers. [ABSTRACT FROM AUTHOR]

Objectives: Biogenic amines modulate the honeybees' behavioral development, especially olfactory learning behavior. Diverse behavioral protocols have been developed to investigate the olfactory learning behavior of bees to process appetitive olfaction information. Apis mellifera ligustica is a well-known eusocial insect to examine the olfactory learning behavior. This study evaluated the relationship between olfactory learning success and biogenic amines and uncovered the role of biogenic amines to regulate the olfactory learning behavior of bees. Methods: We used high-performance liquid chromatography (HPLC) with an electrochemical detection (ECD) system to quantify neurotransmitters levels in the bee brain following olfactory learning trials. Furthermore, the bees of the control group and the dopamine flupenthixol blocker injected group were trained to evaluate the olfactory learning performance. Results: Our finding showed that learning success was directly correlated with the levels of DA and serotonin (5-HT), furthermore, bees of the control group showed higher proboscis extension response than dopamine blocker injected group. Taken together, these findings revealed that dopamine (DA) and serotonin (5-HT) could thus act together to define optimal motivational or attentional levels and improve learning success and indicated that dopamine blocker flupenthixol has to modulate influence on the olfactory learning performance of bees. Conclusion: The results strongly imply that biogenic amines can durably modify the learning behavior in future model insects.

The honey bee (Apis mellifera) plays vital ecological roles in the pollination of crops and the maintenance of ecological balance, and adult honey bees may be exposed to exogenous chemicals including heavy metals during their foraging activities. Cadmium (Cd) is regarded as a nonessential toxic metal and is readily accumulated in plants; honey bees can therefore acquire Cd through the collection of contaminated nectar. In the present study, honey bees were chronically exposed to Cd to investigate the effects of sublethal cadmium doses on the olfactory learning and brain gene expression profiles of honey bees. The results showed that Cd-treated bees exhibited significantly impaired olfactory learning performances in comparison with control bees. Moreover, the head weight was significantly lower in Cd-treated bees than in control bees after chronic exposure to Cd. Gene expression profiles between the Cd treatment and the control revealed that 79 genes were significantly differentially expressed. Genes encoding chemoreceptors and olfactory proteins were downregulated, whereas genes involved in response to oxidative stress were upregulated in Cd-treated bees. The results suggest that Cd exposure exerts oxidative stress in the brain of honey bees, and the dysregulated expression of genes encoding chemoreceptors, olfactory proteins, and cytochrome P450 enzymes is probably associated with impaired olfactory learning in honey bees.

The nutritional composition of food is often complex as resources contain a plethora of different chemical compounds, some of them more, some less meaningful to consumers. Plant pollen, a major food source for bees, is of particular importance as it comprises nearly all macro- and micronutrients required by bees for successful development and reproduction. However, perceiving and evaluating all nutrients may be tedious and impair quick foraging decisions. It is therefore likely that nutrient perception is restricted to specific nutrients or nutrient groups. To better understand the role of taste in pollen quality assessment by bees we investigated nutrient perception in the Western honey bee, Apis mellifera. We tested if the bees were able to perceive concentration differences in amino acids, fatty acids, and sterols, three highly important nutrient groups in pollen, via antennal reception. By means of proboscis extension response (PER) experiments with chemotactile stimulation, we could show that honey bees can distinguish between pollen differing in amino and fatty acid concentration, but not in sterol concentration. Bees were also not able to perceive sterols when presented alone. Our finding suggests that assessment of pollen protein and lipid content is prioritized over sterol content.

Honey bees forage for pollen and nectar. Sugar is an important stimulus for foraging and a major source of energy for honey bees. Any differential response of bees to different concentrations of sugary nectar can affect their foraging. The sugar responsiveness of Apis species (Apis dorsata , Apis florea , and Apis cerana) was determined in comparison to that of Apis mellifera by evaluating the proboscis extension response (PER) with eight serial concentrations (0.00001, 0.0001, 0.001, 0.01, 0.1, 0.5, 1.0, and 1.5 M) of sucrose, glucose and fructose. Nectar foragers of bee species (A. dorsata , A. florea , A. cerana, and A. mellifera) exhibited an equal response for sucrose, glucose, and fructose, with no significant differences in their PER at all tested concentrations of these sugars within the same species. The inter-species comparison between Apis species revealed the differential responsiveness to the different concentrations of sugars, and the lowest concentration at which a response occurs was considered as the response threshold of these bee species for sugar solutions. A. mellifera presented significantly higher responsiveness than A. dorsata to low concentrations (0.00001, 0.0001, 0.001, 0.01, and 0.1 M) of sucrose, glucose and fructose. A. mellifera displayed a significantly higher response to water than A. dorsata. A. florea and A. mellifera presented no significant difference in their responsiveness to sucrose, glucose, and fructose at all tested concentrations, and their water responsiveness was also significantly at par but relatively higher in A. mellifera than in A. florea. Likewise, the responsiveness of A. cerana and A. mellifera to different concentrations of sucrose, glucose and fructose was significantly at par with no difference in their water responsiveness. This study represents preliminary research comparing the response of different honey bee species to three sugar types at different concentrations. The results imply that the native species are all better adapted than A. mellifera under local climate conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amitraz is a common acaricide used inside honeybee hive. • Thiacloprid is known low toxic to honey bee. • Sub-lethal doses of amitraz and thiacloprid did not affect bees' motivation. • Single pesticide treatment did not affect the learning and memory of honey bees. • Combined exposure of amitraz and thiacloprid reduced learning, memory and sugar responsiveness of honey bees. Pollinators, honey bees in particular, are continuously exposed to various mixtures of pesticides, which contribute to their population decline. Both amitraz and thiacloprid have been proven less toxic to honey bees and are frequently applied in- and out-hive, respectively. We examined the sub-lethal effects of amitraz, thiacloprid and their sequential exposure on learning, memory and sugar responsiveness in Apis mellifera using the Proboscis extension response (PER). Sub-lethal doses of amitraz (0.1, 0.2 and 0.4 µg/bee) and thiacloprid (0.05, 0.1 and 0.2 µg/bee) were tested. Sub-lethal effects were observed only at the highest doses of each pesticide treatment; amitraz (0.4 µg/bee) and thiacloprid (0.2 µg/bee) but not in lower doses. In sequential treatment of amitraz and thiacloprid, reduced acquisition and memory retention were significant across all tested doses. The same profile was also obtained on sugar responsiveness of foragers. Our results suggest that the sequential exposure would pose higher risk to honey bee compared to single pesticide exposure by reducing the bees' appetitive olfactory learning, memory and sugar acuity more than individual pesticide exposures. [ABSTRACT FROM AUTHOR]

Honeybees rely on nectar as their main source of carbohydrates. Sucrose, glucose, and fructose are the main components of plant nectars. Intriguingly, honeybees express only 3 putative sugar receptors (AmGr1, AmGr2, and AmGr3), which is in stark contrast to many other insects and vertebrates. The sugar receptors are only partially characterized. AmGr1 detects different sugars including sucrose and glucose. AmGr2 is assumed to act as a co-receptor only, while AmGr3 is assumedly a fructose receptor. We show that honeybee gustatory receptor AmGr3 is highly specialized for fructose perception when expressed in Xenopus oocytes. When we introduced nonsense mutations to the respective AmGr3 gene using CRISPR/Cas9 in eggs of female workers, the resulting mutants displayed almost a complete loss of responsiveness to fructose. In contrast, responses to sucrose were normal. Nonsense mutations introduced by CRISPR/Cas9 in honeybees can thus induce a measurable behavioral change and serve to characterize the function of taste receptors in vivo. CRISPR/Cas9 is an excellent novel tool for characterizing honeybee taste receptors in vivo. Biophysical receptor characterization in Xenopus oocytes and nonsense mutation of AmGr3 in honeybees unequivocally demonstrate that this receptor is highly specific for fructose. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ethion and hexaflumuron negatively impacted honey bees after acute exposure. • Ethion inhibited olfactory, visual learning and memory following acute exposure and reduced sucrose consumption and sucrose responsiveness. • Hexaflumuron impaired the bees' ability to olfactory learning and memory, responsiveness to sucrose, and water. Insecticides are a major tool for controlling pest species. Their widespread use results in damage to non-targeted insects, with honey bees particularly at risk. During foraging, honey bees learn and remember floral characteristics that are associated with food. As insect pollinators, honey bees inadvertently contact chemicals which can have multiple negative impacts. The toxicity of two insecticides from different classes, ethion (47.79 mg a.i.L−1) and hexaflumuron (500 mg a.i.L−1), on learning, memory, and sensory perception were evaluated. We found that oral exposure to ethion had adverse effects on learned proboscis extension toward reward-associated odors and colors. In addition, we showed reduced sucrose consumption and sucrose responsiveness after exposure. Hexaflumuron also impaired olfactory learning and memory and decreased responsiveness to sucrose and water. Exposure to sub-lethal concentration of the cholinergic organophosphate insecticide, ethion (47.79 mg a.i.L−1), and the field-recommended concentration of hexaflumuron (500 mg a.i.L−1), significantly impaired behavior involved in foraging. Our results suggest that several behavioral characteristics of honey bees be evaluated when testing an insecticide rather than relying on just one behavioral measure. [ABSTRACT FROM AUTHOR]

Apis mellifera (honeybees) are a well-established model for the study of learning and cognition. A robust conditioning protocol, the olfactory conditioning of the proboscis extension response (PER), provides a powerful but straightforward method to examine the impact of varying stimuli on learning performance. Herein, we provide a protocol that leverages PER for classroom-based community or student engagement. Specifically, we detail how a class of high school students, as part of the Ryukyu Girls Outreach Program, examined the effects of caffeine and dopamine on learning performance in honeybees. Using a modified version of the PER conditioning protocol, they demonstrated that caffeine, but not dopamine, significantly reduced the number of trials required for a successful conditioning response. In addition to providing an engaging and educational scientific activity, it could be employed, with careful oversight, to garner considerable reliable data examining the effects of varying stimuli on honeybee learning.

The Western honeybee (Apis mellifera L.) is one of the most widespread insects with numerous subspecies in its native range. How far adaptation to local habitats has affected the cognitive skills of the different subspecies is an intriguing question that we investigate in this study. Naturally mated queens of the following five subspecies from different parts of Europe were transferred to Southern Germany: A. m. iberiensis from Portugal, A. m. mellifera from Belgium, A. m. macedonica from Greece, A. m. ligustica from Italy, and A. m. ruttneri from Malta. We also included the local subspecies A. m. carnica in our study. New colonies were built up in a common apiary where the respective queens were introduced. Worker offspring from the different subspecies were compared in classical olfactory learning performance using the proboscis extension response. Prior to conditioning, we measured individual sucrose responsiveness to investigate whether possible differences in learning performances were due to differential responsiveness to the sugar water reward. Most subspecies did not differ in their appetitive learning performance. However, foragers of the Iberian honeybee, A. m. iberiensis, performed significantly more poorly, despite having a similar sucrose responsiveness. We discuss possible causes for the poor performance of the Iberian honeybees, which may have been shaped by adaptation to the local habitat.

In several insects, sex-pheromones are essential for reproduction and reproductive isolation. Pheromones generally elicit stereotyped behaviors. In moths, these are attraction to conspecific sex-pheromone sources and deterrence for heterospecific sex-pheromone. Contrasting with these innate behaviors, some results in social insects point toward effects of non-sex-pheromones on perception and learning. We report the effects of sex-pheromone pre-exposure on gustatory perception and habituation (a non-associative learning) in male Agrotis ipsilon moths, a non-social insect. We also studied the effect of Z5-decenyl acetate (Z5), a compound of the sex-pheromone of the related species Agrotis segetum. We hypothesized that conspecific sex-pheromone and Z5 would have opposite effects. Pre-exposure to either the conspecific sex-pheromone or Z5 lasted 15 min and was done either immediately or 24 h before the experiments, using their solvent alone (hexane) as control. In a sucrose responsiveness assay, pre-exposure to the conspecific sex-pheromone had no effect on the dose-response curve at either delays. By contrast, Z5 slightly improved sucrose responsiveness 15 min but not 24 h after pre-exposure. Interestingly, the conspecific sex-pheromone and Z5 had time-dependent effects on gustatory habituation: pre-exposing the moths with Z5 hindered learning after immediate but not 24-h pre-exposure, whereas pre-exposure to the conspecific sex-pheromone hindered learning at 24-h but not immediate pre-exposure. They did not have opposite effects. This is the first time a sex-pheromone is reported to affect learning in a non-social insect. The difference in modulation between conspecific sex-pheromone and Z5 suggests that con- and hetero-specific sex-pheromones act on plasticity through different cerebral pathways. [ABSTRACT FROM AUTHOR]

Adult moths need energy and nutrients for reproducing and obtain them mainly by consuming flower nectar (a solution of sugars and other compounds). Gustatory perception gives them information on the plants they feed on. Feeding and food perception are integrated in the proboscis extension response, which occurs when their antennae touch a sugar solution. We took advantage of this reflex to explore moth sugar responsiveness depending on different parameters (i.e., sex, age, satiety, site of presentation, and composition of the solution). We observed that starvation but not age induced higher response rates to sucrose. Presentation of sucrose solutions in a randomized order confirmed that repeated sugar stimulations did not affect the response rate; however, animals were sometimes sensitized to water, indicating sucrose presentation might induce non-associative plasticity. Leg stimulation was much less efficient than antennal stimulation to elicit a response. Quinine prevented and terminated sucrose-elicited proboscis extension. Males but not females responded slightly more to sucrose than to fructose. Animals of either sex rarely reacted to glucose, but curiously, mixtures in which half sucrose or fructose were replaced by glucose elicited the same response rate than sucrose or fructose alone. Fructose synergized the response when mixed with sucrose in male but not female moths. This is consistent with the fact that nectars consumed by moths in nature are mixtures of these three sugars, which suggests an adaptation to nectar perception. [ABSTRACT FROM AUTHOR]

Background: Thiamethoxam (TMX) represents the second generation of neonicotinoids that has been widely applied in agricultural activities, while how TMX alters the behavior of Apis cerana, an important native honey bee species in China, is not clear. We carried out three independent experiments to study the impact of acute oral treatment of 20 μL TMX at concentrations of 2.4 ppb (0.048 ng/bee) and 10 ppb (0.2 ng/bee) on the homing, flight, learning acquisition and short‐term retention ability of A. cerana. The homing ability was assessed by the catch‐and‐release method, the flight ability was assessed by flight mills, and the learning acquisition and short‐term retention were evaluated by the proboscis extension response method. Results: When treated with 10 ppb of TMX, bees had a significantly higher average homing time, mean flight velocity, flying distance, and flying duration than the control, whereas 2.4 ppb concentration did not cause any significant effect on homing or flight ability. Bees treated with either 2.4 ppb or 10 ppb TMX had significantly lower learning acquisition and short‐term retention ability. Conclusion: Results suggest that acute oral exposure to 10 ppb of TMX altered the short‐distance homing time, flight ability, and learning acquisition and short‐term retention ability. Our study also highlights the concern that acute oral exposure to a low concentration of 2.4 ppb could have consequences on the behavior of A. creana. Those multiple sublethal alterations on A. cerana's behavior indicate that TMX are likely having complex but negative consequences on bee health in the field. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Objectives] Ziegelmann et al. found that 25 mmol·L lithium chloride had an effective mite removal rate as high as 96% and suggested that lithium chloride was a highly efficient substance for mite removal. This study aims to investigate the effects of 25 mmol·L lithium chloride on the sucrose sensitivity, learning and memory of honeybees, and provide a reference for the application of lithium chloride as an acaricide for honeybees. [Methods] We used 50%(w/v) sugar water to draw honeybees to the hive entrance . Honeybees foraging for sugar water were caught and considered to be foragers. We randomly divided these honeybees into five treatment groups and one control. In view of the acclimation period of honeybees to a cage environment, control and treatment groups were both fed 30% (w/v) sugar water ad libitum in an incubator at constant temperature and humidity [(30±1), relative humidity 40%±10%, dark] for 24 h (50 bees per box), then fed 30% (w/v) sugar water ad libitum and 30% (w/v) sugar water containing 25 mmol·L1 lithium chloride ad libitum for 24 h, respectively. Three of the six groups were used to test sensitivity to six different sugar water concentrations (0.1%, 0.3%, 1%, 3%, 10% and 30%), the remaining three groups were used for olfactory-associative learning experiments. Captured foragers were not kept in cages in the laboratory. We randomly divided these bees into control and treatment groups (35 bees per group), both of which received odor-associative learning training. After this bees in both groups were fed 10 μL 30% (w/v) sugar water and 10 μL 30% (w/v) sugar water containing 25 mM lithium chloride. We tested bees' memory after 2 h, with three replicates. [Results] There was no significant difference in mortality between control and treatment groups within 24 h of lithium chloride treatment (P > 0.05). In the sugar water sensitivity test, the proboscis extension response rate for low concentration sugar water (0.1%-3%) was higher in the treatment group than in the control group (0.3%: P < 0.05; 1%: P < 0.01; 3%: P < 0.001). The sucrose response scores (SRS) of the treatment group were also significantly higher than those of the control group (P < 0. 01). In the olfactory associative learning experiment, the proboscis extension response rate of the two groups increased with training time. The proboscis extension response rate of the control group was significantly higher than that of treatment group (P < 0.05) in the second learning test, but the difference in learning ability between the two groups decreased with training frequency, eventually becoming similar. In the 2 h memory experiment, the proboscis extension response rate of the treatment group was significantly higher than that of the control group (P < 0.05). [Conclusion] 25 mmol·L lithium chloride has no acute lethal effect on honeybees. Exposing honeybees to this concentration of lithium chloride for 24 h enhanced their sensitivity to low concentrations of sugar water. Exposure to 25 mmol·L lithium chloride did not affect the learning behavior of honeybees, but did affect their 2 h short-term memory, which may improve their foraging behavior. [ABSTRACT FROM AUTHOR]

• The sugar response threshold for bees exposed to glucose or fructose was determined. • Bees raised in an incubator showed reduced responses to the excluded sugar. • Bees raised in the hive showed equal responses to each sugar. • Forager bees did not shift their responsiveness. • Gustatory experience during development affects responses to sugars. The level of response to sugar plays a role in many aspects of honey bee behavior including age dependent polyethism and division of labor. Bees may tune their sensitivity to sugars so that they maximize collection of high quality nectar, but they must also be able to collect from less profitable sources when high quality food is scarce. However, our understanding of the mechanisms by which bees can change their responsiveness to different sugars remains incomplete. To investigate the plasticity of sensitivity to sugar, bees were raised on different sugars either in vitro or in colonies. Bees raised in the incubator on diets containing mostly either fructose or glucose showed significantly more responsiveness to the majority sugar. In contrast, bees raised in colonies that only foraged on fructose or glucose responded equally well to both sugars. These data suggest that developmental plasticity for responses to sugar is masked by the feeding of worker jelly to larvae and young bees. The production of worker jelly from secretions of the hypopharyngeal and mandibular glands by nurse bees ensures that both glucose and fructose are experienced by young bees so that they respond to both sugars and will be able to exploit all future food sources. [ABSTRACT FROM AUTHOR]

Declines in honey bee populations represent a worldwide concern. The widespread use of neonicotinoid insecticides has been one of the factors linked to these declines. Sublethal doses of a neonicotinoid insecticide, imidacloprid, has been reported to cause olfactory learning deficits in honey bees via impairment of the target organ, the brain. In the present study, olfactory learning of honey bees was compared between controls and imidacloprid-treated bees. The brains of imidacloprid-treated and control bees were used for comparative transcriptome analysis by RNA-Seq to elucidate the effects of imidacloprid on honey bee learning capacity. The results showed that the learning performance of imidacloprid-treated bees was significantly impaired in comparison with control bees after chronic oral exposure to imidacloprid (0.02 ng/μl) for 11 days. Gene expression profiles between imidacloprid treatment and the control revealed that 131 genes were differentially expressed, of which 130 were downregulated in imidacloprid-treated bees. Validation of the RNA-Seq data using qRT-PCR showed that the results of qRT-PCR and RNA-Seq exhibited a high level of agreement. Gene ontology annotation indicated that the oxidation-reduction imbalance might exist in the brain of honey bees due to oxidative stress induced by imidacloprid exposure. KEGG and ingenuity pathway analysis revealed that transient receptor potential and Arrestin 2 in the phototransduction pathway were significantly downregulated in imidacloprid-treated bees, and that five downregulated genes have causal effects on behavioral response inhibition in imidacloprid-treated bees. Our results suggest that downregulation of brain genes involved in immune, detoxification and chemosensory responses may result in decreased olfactory learning capabilities in imidacloprid-treated bees. Unlabelled Image • Olfactory learning of bees was significantly impaired after chronic exposure to imidacloprid. • Brain transcriptome revealed that 130 genes were downregulated in imidacloprid-treated bees. • GO annotation showed that oxidation-reduction imbalance may exist in brain of IMD-treated bees. • Five genes that have causal effects on behavioral response inhibition in bees were revealed by IPA. [ABSTRACT FROM AUTHOR]

• Visual conditioning using the proboscis extension reaction was established in the Eastern honey bee. • Apis cerana and A. mellifera workers can discriminate between two monochromatic lights. • Both species show similar learning performances. • Mid-term memory in A. mellifera is significantly better than in A. cerana. Honey bees are globally distributed and have received increased attention due to their high economic and ecological value for pollination, their exceptional eusocial lifestyle and complex behavioral repertoire. Interestingly, most research on learning and memory in honey bees has been performed in the Western honey bee, Apis mellifera L., and other honey bee species were largely neglected. In the current study, we thus compared visual learning performance of A. mellifera and the Eastern honey bee, A. cerana Fabr., using the proboscis extension response (PER) paradigm. Workers of A. mellifera and A. cerana were differentially conditioned to two monochromatic light stimuli, with peak maxima at 435 and 528 nm. Both honey bee species were able to form an association between the color stimulus and a sugar reward and significantly distinguished between the two color stimuli in a differential discrimination test. However, besides similar performance levels during visual learning, A. cerana showed a reduced mid-term memory (tested after 2 h) compared to A. mellifera. Finally, performance of the visual PER conditioning in our study reached similar levels as found in olfactory PER conditioning, and we thus recommend the visual PER conditioning approach in addition to olfactory conditioning as a useful tool for studying species-specific learning and memory capabilities in honey bees under controlled laboratory conditions. [ABSTRACT FROM AUTHOR]

Abstract Apis mellifera jemenitica is the indigenous race of honey bees in the Arabian Peninsula and is tolerant to local drought conditions. Experiments were undertaken to determine the differences in associative learning and memory of honey bee workers living in the arid zone of Saudi Arabia, utilizing the proboscis extension response (PER). These experiments were conducted on the indigenous race (A. m. jemenitica) along with two introduced European races (A. m. carnica and A. m. ligustica). The data revealed that A. m. jemenitica is amenable to PER conditioning and may be used in conditioning experiments within the olfactory behavioral paradigm. The results also demonstrated that the three races learn and retain information with different capacities relative to each other during the experimental time periods. Native Arabian bees (A. m. jemenitica) exhibited significantly lower PER percentage during second and third conditioning trials when compared to exotic races. Apis mellifera jemenitica also exhibited reduced memory retention at 2 h and 24 h when compared to A. m. carnica and A. m. ligustica. Therefore, the native Arabian bees were relatively slow learners with reduced memory retention compared to the other two races that showed similar learning and memory retention. Three or five conditioning trials and monthly weather conditions (October and December) had no significant effects on learning and memory in A. m. jemenitica. These results emphasized a novel line of research to explore the mechanism and differences in associative learning as well as other forms of learning throughout the year among bee races in the harsh arid conditions of Saudi Arabia. This is the first study in Saudi Arabia to demonstrate inter-race differences regarding olfactory associative learning between native Arabian bees and two introduced European honey bee races. [ABSTRACT FROM AUTHOR]

Honeybees are valuable pollinators strongly influencing ecosystem conservation, stability, genetic variation and ecological relationships in the floral diversity, plant community, evolution, and specialization. Honeybee is an excellent model organism for research on learning and memory among invertebrates. In their behavior, the subjective evaluation of a sucrose stimulus influences the behavioral performance. Here we report comparative behavioral data on the sensitization, habituation, short-term and long-term memory of Apis cerana and A. mellifera in China, using different sucrose concentrations. A. mellifera foragers have higher sucrose responsiveness than A. cerana foragers when tested using a proboscis extension response (PER) assay. Sensitization and habituation are well-known forms of nonassociative learning. A. cerana took less number of habituation trials as compared to A. mellifera. Thus, these results significantly showed that A. cerana took less time to dishabituate. The sensitive stimuli of A. cerana against lemon extract were more than A. mellifera. In addition, although A. mellifera showed more sensitive stimuli against apple extract than A. cerana cerana, A. mellifera displayed significantly more learning and memory behavior than A. cerana after 2 and 24 hours. [ABSTRACT FROM AUTHOR]

Honeybees show lateral asymmetry in both learning about odors associated with reward and recalling memory of these associations. We have extended this research to show that bees exhibit lateral biases in their initial response to odors: viz., turning toward the source of an odor presented on their right side and turning away from it when presented on their left side. The odors we presented were the main component of the alarm pheromone, isoamyl acetate (IAA), and four floral scents. The significant bias to turn toward IAA odor on the right and away from it on the left is, we argue, a lateralization of the fight-flight response elicited by this pheromone. It contrasts to an absence of any asymmetry in the turning response to an odor of the flowers on which the bees had been feeding prior to testing: to this odor they turned toward when it was presented on either the left or right side. Lemon and orange odors were responded to differently on the left and right sides (toward on the right, away on the left), but no asymmetry was found in responses to rose odor. Our results show that side biases are present even in the initial, orienting response of bees to certain odors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixture of acetamiprid and emamectin benzoate is more toxic to both A. mellifera adult and larval than either insecticide alone. • Spraying the mixture of acetamiprid and emamectin benzoate results in higher toxicity than oral ingestion. • Acetamiprid and emamectin benzoate have an additive effect that increases their toxicity on bees. • Emamectin benzoate alone and in combination with acetamiprid have a significant impact on the learning and memory of honey bees. The neonicotinoid acetamiprid (ACE) and emamectin benzoate (EMB) are widely utilized agrochemicals worldwide in crop protection. Most previous studies have evaluated on the toxicity of individual insecticides on honeybees. This study evaluated formulation of combined toxicities of acetamiprid (8%) and emamectin benzoate (2.15%) through oral and contact exposures to Apis mellifera. The binary mixture had a lethal dose (LD 50) of 1 × 10−3 µg/bee (oral) and 4 × 10−5 µg/bee (contact) to adult honeybees and a lethal concentration (LC 50) of 2 × 10−1 µg/ml to larvae. The mixture's oral and contact hazard quotient were significantly greater than ACE, with values of 17,400 and 5000, respectively. The estimated additive indices (AI) showed that ACE and EMB interacted additively with AI values of 0.047 (oral), 0.01 (contact), and 0.02 (larval). The mixture also reduced the survival of larvae, affected proboscis extension response (PER) scores, and impacted the ability of honeybees to discriminate odors. The authors recommend a field study to investigate the mixture's adverse effects on honeybees further. [ABSTRACT FROM AUTHOR]

Honey bees transfer different informational components of the discovered feeding source to their nestmates during the waggle dance. To decode the multicomponent information of this complex behavior, dance followers have to attend to the most relevant signal elements while filtering out less relevant ones. To achieve that, dance followers should present improved abilities to acquire information compared with those bees not engaged in this behavior. Through proboscis extension response assays, sensory and cognitive abilities were tested in follower and non-follower bees. Individuals were captured within the hive, immediately after following waggle runs or a bit further from the dancer. Both behavioral categories present low and similar spontaneous odor responses (SORs). However, followers exhibit differences in responsiveness to sucrose and odor discrimination: followers showed increased gustatory responsiveness and, after olfactory differential conditioning, better memory retention than non-followers. Thus, the abilities of the dance followers related to appetitive behavior would allow them to improve the acquisition of the dance surrounding information.

Lateralization is a fundamental property of the human brain that affects perceptual, motor, and cognitive processes. It is now acknowledged that left–right laterality is widespread across vertebrates and even some invertebrates such as fruit flies and bees. Honeybees, which learn to associate an odorant (the conditioned stimulus, CS) with sucrose solution (the unconditioned stimulus, US), recall this association better when trained using their right antenna than they do when using their left antenna. Correspondingly, olfactory sensilla are more abundant on the right antenna and odor encoding by projection neurons of the right antennal lobe results in better odor differentiation than those of the left one. Thus, lateralization arises from asymmetries both in the peripheral and central olfactory system, responsible for detecting the CS. Here, we focused on the US component and studied if lateralization exists in the gustatory system of Apis mellifera. We investigated whether sucrose sensitivity is lateralized both at the level of the antennae and the fore-tarsi in two independent groups of bees. Sucrose sensitivity was assessed by presenting bees with a series of increasing concentrations of sucrose solution delivered either to the left or the right antenna/tarsus and measuring the proboscis extension response to these stimuli. Bees experienced two series of stimulations, one on the left and the other on the right antenna/tarsus. We found that tarsal responsiveness was similar on both sides and that the order of testing affects sucrose responsiveness. On the contrary, antennal responsiveness to sucrose was higher on the right than on the left side, and this effect was independent of the order of antennal stimulation. Given this asymmetry, we also investigated antennal lateralization of habituation to sucrose. We found that the right antenna was more resistant to habituation, which is consistent with its higher sucrose sensitivity. Our results reveal that the gustatory system presents a peripheral lateralization that affects stimulus detection and non-associative learning. Contrary to the olfactory system, which is organized in two distinct brain hemispheres, gustatory receptor neurons converge into a single central region termed the subesophagic zone (SEZ). Whether the SEZ presents lateralized gustatory processing remains to be determined.

Many flowering plants present variable complex fragrances, which usually include different isomers of the same molecule. As fragrance is an essential cue for flower recognition by pollinators, we ask whether honey bees discriminate between floral-fragrance isomers in an appetitive context. We used the olfactory conditioning of the proboscis extension response, which allows training a restrained bee to an odor paired with sucrose solution. Bees were trained under an absolute (a single odorant rewarded) or a differential conditioning regime (a rewarded versus a non-rewarded odorant) using four different pairs of isomers. One hour after training, discrimination and generalization between pairs of isomers were tested. Bees trained under absolute conditioning exhibited high generalization between isomers and discriminated only one out of four isomer pairs; after differential conditioning, they learned to differentiate between two out of four pairs of isomers but in all cases generalization responses to the non-rewarding isomer remained high. Adding an aversive taste to the non-rewarded isomer facilitated discrimination of isomers that otherwise seemed non-discriminable but generalization remained high. Although honey bees discriminated isomers under certain conditions, they achieved the task with difficulty and tended to generalize between them, thus showing that these molecules were perceptually similar to them. We conclude that the presence of isomers within floral fragrances might not necessarily contribute to a dramatic extent to floral odor diversity. [ABSTRACT FROM AUTHOR]

Honeybees ( Apis mellifera ) are well-known for their sophisticated division of labor with each bee performing sequentially a series of social tasks. Colony organization is largely based on age-dependent division of labor. While bees perform several tasks inside the hive such as caring for brood (“nursing”), cleaning or sealing brood cells or producing honey, older bees leave to colony to collect pollen (proteins) and nectar (carbohydrates) as foragers. The most pronounced behavioral transition occurs when nurse bees become foragers. For both social roles, the detection and evaluation of sugars is decisive for optimal task performance. Nurse bees rely on their gustatory senses to prepare brood food, while foragers evaluate a nectar source before starting to collect food from it. To test whether social organization is related to differential sensing of sugars we compared the taste of nurse bees and foragers for different sugars. Searching for molecular correlates for differences in sugar perception, we further quantified expression of gustatory receptor genes in both behavioral groups. Our results demonstrate that nurse bees and foragers perceive and evaluate different sugars differently. Both groups, however, prefer sucrose over fructose. At least part of the taste differences between social roles could be related to a differential expression of taste receptors in the antennae and brain. Our results suggest that differential expression of sugar receptor genes might be involved in regulating division of labor through nutrition-related signaling pathways. [ABSTRACT FROM AUTHOR]

Lateralization is a fundamental property of the human brain that affects perceptual, motor, and cognitive processes. It is now acknowledged that left-right laterality is widespread across vertebrates and even some invertebrates such as fruit flies and bees. Honeybees, which learn to associate an odorant (the conditioned stimulus, CS) with sucrose solution (the unconditioned stimulus, US), recall this association better when trained using their right antenna than they do when using their left antenna. Correspondingly, olfactory sensilla are more abundant on the right antenna and odor encoding by projection neurons of the right antennal lobe results in better odor differentiation than those of the left one. Thus, lateralization arises from asymmetries both in the peripheral and central olfactory system, responsible for detecting the CS. Here, we focused on the US component and studied if lateralization exists in the gustatory system of Apis mellifera. We investigated whether sucrose sensitivity is lateralized both at the level of the antennae and the fore-tarsi in two independent groups of bees. Sucrose sensitivity was assessed by presenting bees with a series of increasing concentrations of sucrose solution delivered either to the left or the right antenna/tarsus and measuring the proboscis extension response to these stimuli. Bees experienced two series of stimulations, one on the left and the other on the right antenna/tarsus. We found that tarsal responsiveness was similar on both sides and that the order of testing affects sucrose responsiveness. On the contrary, antennal responsiveness to sucrose was higher on the right than on the left side, and this effect was independent of the order of antennal stimulation. Given this asymmetry, we also investigated antennal lateralization of habituation to sucrose. We found that the right antenna was more resistant to habituation, which is consistent with its higher sucrose sensitivity. Our results reveal that the gustatory system presents a peripheral lateralization that affects stimulus detection and non-associative learning. Contrary to the olfactory system, which is organized in two distinct brain hemispheres, gustatory receptor neurons converge into a single central region termed the subesophagic zone (SEZ). Whether the SEZ presents lateralized gustatory processing remains to be determined. [ABSTRACT FROM AUTHOR]

Our aim was to determine whether honey bees use pollen to distinguish between staminate and pistillate kiwifruit flowers, and, if so, why they find pistillate flowers more attractive. Bees differentiated between staminate and pistillate flowers when the petals and stigma were removed. In trials using artificially collected staminate and pistillate pollen, bees responded by extending their proboscis to pistillate pollen at significantly higher rates in one out of two trials. Bees were trained to increase their response to staminate pollen, indicating their ability to differentiate the two pollens. There was no difference in the amount of sugar in staminate versus pistillate kiwifruit pollen pellets, suggesting that bees treat them the same during collection. Pistillate pollen grains were significantly lighter than staminate grains, which may influence honey bees’ preference for foraging on pistillate flowers. The proboscis extension response to pollen could be used to select staminate vines in breeding programmes. [ABSTRACT FROM PUBLISHER]

All animals constantly negotiate external with internal demands before and during action selection. Energy homeostasis is a major internal factor biasing action selection. For instance, in addition to physiologically regulating carbohydrate mobilization, starvation-induced sugar shortage also biases action selection toward food-seeking and food consumption behaviors (the counter-regulatory response). Biogenic amines are often involved when such widespread behavioral biases need to be orchestrated. In mammals, norepinephrine (noradrenalin) is involved in the counterregulatory response to starvation-induced drops in glucose levels. The invertebrate homolog of noradrenalin, octopamine (OA) and its precursor tyramine (TA) are neuromodulators operating in many different neuronal and physiological processes. Tyrosine-ß-hydroxylase (tßh) mutants are unable to convert TA into OA. We hypothesized that tßh mutant flies may be aberrant in some or all of the counter-regulatory responses to starvation and that techniques restoring gene function or amine signaling may elucidate potential mechanisms and sites of action. Corroborating our hypothesis, starved mutants show a reduced sugar response and their hemolymph sugar concentration is elevated compared to control flies. When starved, they survive longer. Temporally controlled rescue experiments revealed an action of the OA/TA-system during the sugar response, while spatially controlled rescue experiments suggest actions also outside of the nervous system. Additionally, the analysis of two OA- and four TA-receptor mutants suggests an involvement of both receptor types in the animals' physiological and neuronal response to starvation. These results complement the investigations in Apis mellifera described in our companion paper (Buckemüller et al., 2017).

All animals constantly negotiate external with internal demands before and during action selection. Energy homeostasis is a major internal factor biasing action selection. For instance, in addition to physiologically regulating carbohydrate mobilization, starvation-induced sugar shortage also biases action selection toward food-seeking and food consumption behaviors (the counter-regulatory response). Biogenic amines are often involved when such widespread behavioral biases need to be orchestrated. In mammals, norepinephrine (noradrenalin) is involved in the counterregulatory response to starvation-induced drops in glucose levels. The invertebrate homolog of noradrenalin, octopamine (OA) and its precursor tyramine (TA) are neuromodulators operating in many different neuronal and physiological processes. Tyrosine-ß-hydroxylase (tßh) mutants are unable to convert TA into OA. We hypothesized that tßh mutant flies may be aberrant in some or all of the counter-regulatory responses to starvation and that techniques restoring gene function or amine signaling may elucidate potential mechanisms and sites of action. Corroborating our hypothesis, starved mutants show a reduced sugar response and their hemolymph sugar concentration is elevated compared to control flies. When starved, they survive longer. Temporally controlled rescue experiments revealed an action of the OA/TA-system during the sugar response, while spatially controlled rescue experiments suggest actions also outside of the nervous system. Additionally, the analysis of two OA- and four TA-receptor mutants suggests an involvement of both receptor types in the animals' physiological and neuronal response to starvation. These results complement the investigations in Apismellifera described in our companion paper (Buckemüller et al., 2017). [ABSTRACT FROM AUTHOR]

Honeybees are well known for their complex division of labor. Each bee sequentially performs a series of social tasks during its life. The changes in social task performance are linked to gross differences in behavior and physiology. We tested whether honeybees performing different social tasks (nursing versus foraging) would differ in their gustatory responsiveness and associative learning behavior in addition to their daily tasks in the colony. Further, we investigated the role of the biogenic amine tyramine and its receptors in the behavior of nurse bees and foragers. Tyramine is an important insect neurotransmitter, which has long been neglected in behavioral studies as it was believed to only act as the metabolic precursor of the better-known amine octopamine. With the increasing number of characterized tyramine receptors in diverse insects, we need to understand the functions of tyramine on its own account. Our findings suggest an important role for tyramine and its two receptors in regulating honeybee gustatory responsiveness, social organization and learning behavior. Foragers, which were more responsive to gustatory stimuli than nurse bees and performed better in appetitive learning, also differed from nurse bees in their tyramine brain titers and in the mRNA expression of a tyramine receptor in the brain. Pharmacological activation of tyramine receptors increased gustatory responsiveness of nurse bees and foragers and improved appetitive learning in nurse bees. These data suggest that a large part of the behavioral differences between honeybees may be directly linked to tyramine signaling in the brain. [ABSTRACT FROM AUTHOR]

Amitraz, an acaricide used to treat Varroa destructor Anderson & Trueman, is one of the most commonly detected pesticides in honey bee (Apis mellifera L.) hives. Acaricides sometimes negatively impact honey bee cognition, but potential effects of amitraz on honey bee learning have been rarely studied. We topically exposed foragers to 95th percentile field-relevant levels of amitraz and, 24 h later, tested the ability of bees to associate a sucrose reward with a conditioned odor (learning response) using the proboscis extension response (PER). We then tested the ability of the bees to retain this memory 1 h and 2 h post-conditioning. Because amitraz is thought to affect octopamine metabolism in honey bees, and because octopamine is directly related to honey bee learning and memory, we also examined effects of exposure to amitraz on octopamine levels in honey bee hemolymph. We found that acute exposure to 95th percentile doses of amitraz had no impact on honey bee learning or short-term memory as measured by PER. Concentrations of octopamine in hemolymph from our low amitraz treatment were 1.4-fold higher than control levels, but other treatments had no effect. Our results from worst-case acute exposure experiments with worker bees in the laboratory suggest that typical fieldrelevant (within hive) exposures to amitraz probably have little effect on honey bee learning and memory. [ABSTRACT FROM AUTHOR]

In recent years, many pollinators have declined in abundance and diversity worldwide, presenting a potential threat to agricultural productivity, biodiversity and the functioning of natural ecosystems. One of the most debated factors proposed to be contributing to pollinator declines is exposure to pesticides, particularly neonicotinoids, a widely used class of systemic insecticide. Also, newly emerging parasites and diseases, thought to be spread via contact with managed honeybees, may pose threats to other pollinators such as bumblebees. Compared to honeybees, bumblebees could be particularly vulnerable to the effects of stressors due to their smaller and more short-lived colonies. Here, we studied the effect of field-realistic, chronic clothianidin exposure and inoculation with the parasite Nosema ceranae on survival, fecundity, sugar water collection and learning using queenless Bombus terrestris audax microcolonies in the laboratory. Chronic exposure to 1 ppb clothianidin had no significant effects on the traits studied. Interestingly, pesticide exposure in combination with additional stress caused by harnessing bees for Proboscis Extension Response (PER) learning assays, led to an increase in mortality. In contrast to previous findings, the bees did not become infected by N. ceranae after experimental inoculation with the parasite spores, suggesting variability in host resistance or parasite virulence. However, this treatment induced a slight, short-term reduction in sugar water collection, potentially through stimulation of the immune system of the bees. Our results suggest that chronic exposure to 1 ppb clothianidin does not have adverse effects on bumblebee fecundity or learning ability.