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Phototactic behaviour correlates with gustatory responsiveness in honey bees (Apis mellifera L.).

The response threshold hypothesis of division of labour in honey bees assumes that individuals differ in their responsiveness to different stimulus modalities. However, previous experiments have shown that responsiveness to gustatory stimuli correlates with responsiveness to odours, pollen and tactile stimuli. Evaluation of these stimuli involves sensory receptors on the antenna. We tested whether responsiveness to gustatory stimuli correlates with responsiveness to visual stimuli in a phototaxis experiment, which is independent of antennal input. Gustatory responsiveness was measured using the proboscis extension response to antennal stimulation with water and different sucrose concentrations. Phototaxis was quantified by measuring the walking times a bee needed to reach light sources of different intensities. Walking behaviour in the darkness was measured to test for differences in locomotor behaviour. The walking time towards a light stimulus, the path length, and the walking speed depended on the intensity of the light stimulus. Responsiveness to visual stimuli correlated significantly with gustatory responsiveness. Bees displaying a high gustatory responsiveness were also very sensitive to light. Locomotor activity did not correlate with gustatory responsiveness. This shows that gustatory responsiveness is a good indicator of sensitivity for visual stimuli, which are not perceived by the antenna.

Analysis of Variance↗

Nicotine injected into the antennal lobes induces a rapid modulation of sucrose threshold and improves short-term memory in the honeybee Apis mellifera.

In honeybee, although it is known that the food perception and the olfactory memory can be modulated by many environmental and biochemical factors, nothing is known on the effects of nicotine on these processes. Using microinjections of nicotine in the antennal lobes, we show that nicotine at 10(-3) M and 10(-4) M but not at 10(-5) M induced an increase of sucrose sensitivity and that post-training injection of 10(-5) M nicotine improved retention of olfactory learning. These results demonstrate that potentiation of the cholinergic system in the honeybee enhances sucrose perception and facilitates olfactory memory.

Animals↗

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA.

Phenoloxidase (monophenol, l-dopa: oxygen oxidoreductase, EC 1.14.18.1) is a multicopper oxidase, which plays an important role in melanin synthesis, necessary for defense against intruding microorganisms and parasites, wound healing and cuticle pigmentation. A phenoloxidase from the hemolymph of honey bee pupae exhibited an apparent molecular mass of 70 kDa, as estimated by gel filtration and SDS-PAGE. Optimal pH and temperature were 6.5 and 20 degrees C, respectively. Activity was fully stable for 30 min at 50 degrees C. Like phenoloxidases from the hemolymph of other insects, the honey bee enzyme was activated by trypsin and inhibited by protease inhibitors and phenylthiourea. Only high concentrations of sodium azide effectively inhibited the detected activity. A low concentration (5 microM) of Ca2+, Mg2+, and Mn2+ had a stimulatory effect on the activity. Single Michaelis-Menten curves were observed for l-dopa and dopamine oxidation, but the affinity of the enzyme for dopamine was greater than for L-dopa. Semiquantitative RT-PCR and Southern blot analysis using a 359 bp labeled probe, and quantification of the prophenoloxidase mRNA levels by real-time PCR showed increased amounts of transcripts in hemocytes and integument from young pupae injected with 20-hydroxyecdysone.

Animals↗

Visual resolution of the orientation cue by the honeybee (Apis mellifera).

Bees were trained to discriminate between a pattern with two or more black bars and a similar pattern with the bars at right angles. Earlier measures of the resolution of oblique black and white regular gratings of different periods were confirmed. The positions of the training bars were shifted every 5 min to prevent the bees from using their locations as cues. To measure the length of the detectors of edge orientation, the trained bees were tested with targets filled with parallel short black/white edges of various lengths. The minimum individual length of edge required to discriminate the orientation cue was found to be near 3 degrees, and similar for vertical, horizontal and oblique edges. This is the first time that this kind of resolution has been measured in an invertebrate. The bees learn and recognize the edge orientation, not the lay-out of the pattern.

Animals↗

Octopamine receptors in the honeybee (Apis mellifera) brain and their disruption by RNA-mediated interference.

Octopamine plays important neuromodulatory roles in the honeybee brain. Accordingly, mRNA from a recently identified honeybee octopamine receptor (AmOA1) is distributed throughout the brain. We have evaluated the occurrence of AmOA1 in the antennal lobe (AL) as well as rest of the brain (RB) by western blotting using an antiserum raised against a peptide selected from AmOA1 sequence. In addition to an expected band (78 kDa in the AL), one additional band (72 kDa) was identified from the AL and four bands (48, 60, 72 and 78 kDa) were observed in the RB. These bands were also recognized with antiserum against a different peptide segment from an octopamine receptor ortholog from the fruitfly (OAMB). Significant sequence identity with the peptide segment used to generate the antiserum was only found with OAMB and its splice variants in fruitfly; it was less conserved in other biogenic amine receptors from honeybee and other insects. Furthermore, western blot analysis performed on brains with dsRNA-treated antennal lobes showed a decrease in the intensity of all four bands. This suggests that AmOA1 antiserum specifically recognizes one or more types of AmOA1 receptors in the honeybee brain. We extend our earlier study of RNAi to quantify the rate of spread of dsRNA from a localized injection to other neuropils.

Amino Acid Sequence↗

Social versus individual behaviour: a comparative approach to thermal behaviour of the honeybee (Apis mellifera L.) and the American cockroach (Periplaneta americana L.).

To study the relationship between the individual and social thermoregulatory behaviour, we used honeybee workers and American cockroaches. Single insects or groups of 10-20 individuals were placed in a temperature gradient chamber, and their thermal preference was recorded for 48 h under natural summer photoperiod. Single bees showed diurnal changes in selected ambient temperature, which culminated at 14:00 reaching 34+/-2 degrees C, and then slowly decreased, reaching a nocturnal minimum of 28+/-2 degrees C at 04:00. In contrast, the zenith of temperature selected by groups of bees (31+/-1 degrees C) was reached at 04:00 and the nadir (29+/-2 degrees C) was recorded at 14:00. Groups of bees clustered together during the night time, and dispersed during intense day time activity. Such changes were absent in groups of cockroaches. Cockroaches selected an ambient temperature of 30+/-1 degrees C both during day and night. In conclusion, there is a striking analogy in the diurnal thermal behaviour between a colony of bees and mammals. During their nychthemeral rest phase, both of them select higher temperatures than during the activity phase and, simultaneously, they reduce their overall surface area of heat loss to conserve metabolic heat. Therefore, the colony behaves as a homeothermic superorganism. In contrast, a single bee, isolated from the colony, utilizes a heterothermic strategy to save energy for a morning warm up.

Analysis of Variance↗

Volatile compounds emitted by live European honey bee (Apis mellifera L.) queens.

We used solid-phase microextraction (SPME, 65 microm PDMS-DVB fiber) to sample the volatile compounds emitted by live honey bee queens in several reproductive states (unmated queens, recently mated queens, and established mated queens), and compared them to the volatiles emitted by workers. We detected nine compounds that were present in at least 75% of the individuals in at least one type of bee, and which were not present in the sampling environment alone. Four of these compounds were present in queens but not in workers. One of these four compounds, identified as E-beta-ocimene, was expressed fully only in established mated queens and may be a signal of diploid egg-laying activity. The three remaining queen-specific compounds (including one identified as 2-phenylethanol) were associated with unmated queens and may mediate interactions between unmated queens and workers during queen elimination. The five common compounds that we detected in both queens and workers were hydrocarbons and may function as nestmate recognition cues. We consider these discoveries as a first step in determining the potentially important functions of volatile signals and cues within honey bee nests.

Acyclic Monoterpenes↗

Visual discriminations of spokes, sectors, and circles by the honeybee (Apis mellifera).

A new cue for visual discrimination by the honeybee has been demonstrated. Bees detected the position of the centre of symmetry of radial patterns of spokes, sectors, and circles relative to their point of choice in the learning process, irrespective of the pattern. When trained with one of these patterns versus a blank target, the bees discriminated a shift in the position of the centre of symmetry by as little as 5 degrees , in some cases with unfamiliar test patterns. A pattern of spokes or rings also stabilized the vision of the bees in the horizontal plane so that the position of a plain black area could then be discriminated. In other experiments, bees discriminated half of a pattern of radial spokes or concentric circles from the other half, cut either vertically or horizontally, and irrespective of scale. Therefore these patterns were not detected by preformed combinations of orientation detectors or global templates with a single output. Instead, the crucial cue for detecting edges as radial or circular was the coincidence of responses of numerous local edge detectors having the appropriate convergence to a hub. Edges that converged towards a hub were detected by the bees as radial, and edges at right angles to these were parts of circles, irrespective of the actual pattern. Breaking the patterns of spokes or circles into rows of squares spoiled the discrimination if the squares were separately resolved. Alternatively, breaking the pattern into short bars that were separately resolved spoiled the discrimination when the bars subtended less than 3 degrees . The local feature detectors for spokes and circles therefore resembled those of the orientation detectors in being short, independent, and unable to span gaps of more than 3 degrees . In conclusion, radial and circular patterns were identified by the regional coincidences and convergence of local detectors of edge orientation, and the positions of the centres of symmetry were remembered as landmarks that helped locate the reward, but the patterns themselves were not remembered.

Animals↗

Octopamine and tyramine influence the behavioral profile of locomotor activity in the honey bee (Apis mellifera).

The biogenic amines octopamine and tyramine are believed to play a number of important roles in the behavior of invertebrates including the regulation of motor function. To investigate the role of octopamine and tyramine in locomotor behavior in honey bees, subjects were injected with a range of concentrations of octopamine, tyramine, mianserin or yohimbine. Continuous observation of freely moving worker bees was used to examine the effects of these treatments on the amount of time honey bees spent engaged in different locomotor behaviors such as walking, grooming, fanning and flying. All treatments produced significant shifts in behavior. Decreases in time spent walking and increases in grooming or stopped behavior were observed for every drug. However, the pattern of the shift depended on drug, time after injection and concentration. Flying behavior was differentially affected with increases in flying seen in octopamine treated bees, whereas those receiving tyramine showed a decrease in flying. Taken together, these data provide evidence that octopamine and tyramine modulate motor function in the honey bee perhaps via interaction with central pattern generators or through effects on sensory perception.

Animals↗

Acute ethanol ingestion produces dose-dependent effects on motor behavior in the honey bee (Apis mellifera).

Ethanol consumption produces characteristic behavioral states in animals that include sedation, disorientation, and disruption of motor function. Using individual honey bees, we assessed the effects of ethanol ingestion on motor function via continuous observations of their behavior. Consumption of 1 M sucrose solutions containing a range of ethanol doses led to hemolymph ethanol levels of approximately 40-100 mM. Using ethanol doses in this range, we observed time and dose-dependent effects of ethanol on the percent of time our subjects spent walking, stopped, or upside down, and on the duration and frequency of bouts of behavior. The effects on grooming and flying behavior were more complex. Behavioral recovery from ethanol treatment was both time and ethanol dose dependent, occurring between 12 and 24 h post-ingestion for low doses and at 24-48 h for higher doses. Furthermore, the amount of ethanol measured in honey bee hemolymph appeared to correlate with recovery. We predict that the honey bee will prove to be an excellent model system for studying the influence of ethanol on the neural mechanisms underlying behavior.

Animals↗

Some labels that are recognized on landmarks by the honeybee (Apis mellifera).

Freely flying bees were trained in a situation that resembled the natural task of a bee arriving at a foraging site that was located by a landmark. The bees' task was to locate the reward in the arm of the Y-choice apparatus, where a black pattern on a white background was displayed in one arm versus a white target in the other arm, at a range of 27 cm. The alternative patterns for the training included previously identified cues. They were: an oblique bar, three parallel oblique bars, an oblique grating, a square cross, six spokes, a large or a small spot, a spotty modulation, or a ring. The trained bees were given a variety of interleaved tests to discover the labels they had used to identify the patterns. A label is defined as the coincidence of cues that contributed to the recognition of a single landmark. The bees learned, firstly, the black area at the expected place, secondly, modulation caused by edges at the expected place. These cues were quantified and always available. In addition, the orientation cue was learned from a grating that covered the target, but was ignored in a single bar. The bees learned the positions of the centres of black and of radial symmetry. In tests, they also recognized unfamiliar cues that were not displayed in the training. The cues and preferences were similar to those used to discriminate between two targets. The new experiments validate some old conclusions that have been controversial for 40 years.

Animals↗

A scientific note on the detection of honeybee viruses using real-time PCR (TaqMan) in Varroa mites collected from a Thai honeybee (Apis mellifera) apiary.

Bee parasitic mite syndrome is a disease complex of colonies simultaneously infested with Varroa destructor mites and infected with viruses and accompanied by high mortality. By using real-time PCR (TaqMan), five out of seven bee viruses were detected in mite samples (V. destructor) collected from Thailand. Moreover, the results of this study provide an evidence for the co-existence of several bee viruses in a single mite. This is also the first report of bee viruses in mites from Thailand.

Animals↗

Horizontal and vertical transmission of viruses in the honey bee, Apis mellifera.

The most crucial stage in the dynamics of virus infections is the mode of virus transmission. In general, transmission of viruses can occur through two pathways: horizontal and vertical transmission. In horizontal transmission, viruses are transmitted among individuals of the same generation, while vertical transmission occurs from mothers to their offspring. Because of its highly organized social structure and crowded population density, the honey bee colony represents a risky environment for the spread of disease infection. Like other plant and animal viruses, bee viruses use different survival strategies, including utilization of both horizontal and vertical routes, to transmit and maintain levels in a host population. In this review, we explore the current knowledge about the honey bee viruses and transmission routes of bee viruses. In addition, different transmission strategies on the persistence and dynamics of host-pathogen interactions are also discussed.

Animals↗

Proteome Unravels Mechanism Differences in Embryogenesis Between Honey Bee Drone and Worker (Apis mellifera L.).

The physiological and social behaviors differ widely between honeybee workers and drones. All the organ rudiments of adult bees are formed during the embryonic stage. The initial molecular bases at the proteomic level for both embryonic developments have been identified, but a comprehensive understanding of the significant events involved in embryonic establishment remains elusive. To elucidate the molecular regulatory mechanisms underlying tissue differentiation during the embryogenesis of drones and workers, we implemented a state-of-the-art approach that combines in-hive inspection and targeted sampling (at nine embryogenesis stages) with high-throughput proteomics technology to investigate the developmental differences. In-hive inspection of hatching timing revealed an average developmental gap of approximately 3.6 h between the two embryos. Furthermore, proteomic analyses indicate that drone and worker embryos adopt distinct developmental strategies. Notably, proteins involved in fatty acid metabolism and key biological pathways related to organ formation-such as the Hedgehog and Wnt signaling pathways-are activated earlier in drones, suggesting that tissue development begins sooner in drone embryos than in workers. Additionally, the upregulation of cytoskeletal proteins and antioxidants in drone embryos likely supports their larger cell size and higher metabolic stress, reflecting distinct molecular characteristics of male development. Ribosomal proteins essential for biosynthetic support remain consistently expressed throughout the late stages in male embryos, indicating that drone embryogenesis lasts longer than that of workers. This work provides novel insights into the molecular foundations of honeybee embryogenesis and lays both theoretical and practical groundwork for future research into the mechanisms driving embryonic development.

Animals↗

Characterization of the two distinct subtypes of metabotropic glutamate receptors from honeybee, Apis mellifera.

L-Glutamate is a major neurotransmitter at the excitatory synapses in the vertebrate brain. It is also the excitatory neurotransmitter at neuromuscular junctions in insects, however its functions in their brains remain to be established. We identified and characterized two different subtypes (AmGluRA and AmGluRB) of metabotropic glutamate receptors (mGluRs) from an eusocial insect, honeybee. Both AmGluRA and AmGluRB form homodimers independently on disulfide bonds, and bind [3H]glutamate with K(D) values of 156.7 and 80.7 nM, respectively. AmGluRB is specifically expressed in the brain, while AmGluRA is expressed in the brain and other body parts, suggesting that AmGluRA is also present at the neuromuscular junctions. Both mGluRs are expressed in the mushroom bodies and the brain regions of honeybees, where motor neurons are clustered. Their expression in the brain apparently overlaps, suggesting that they may interact with each other to modulate the glutamatergic neurotransmission.

Amino Acid Sequence↗

Effects of caffeine on olfactory and visual learning in the honey bee (Apis mellifera).

Although caffeine is known to improve alertness and arousal in humans and other mammals, its impacts on specific behaviours, including complex cognitive processes, remain controversial. We reasoned that the availability of an easily manipulable, but behaviourally complex invertebrate organism with a simpler nervous system would be beneficial to this field of research. We used a popular behavioural model, the honeybee, to evaluate the effects of caffeine on (1) the development of olfactory learning and (2) the performance in complex learning paradigms, including a 'delayed-match-to-sample' task and visual associative learning. To evaluate the efficacy of caffeine treatment, a variety of doses (0.4-400 ng/1 mg of body mass) were applied topically to tethered individuals. Behavioural testing was performed with either tethered or free-flying adult honeybees. We show that caffeine has marked cognitive effects in this species. In young honeybees, it reduces the age at which restrained individuals are able to learn an olfactory associative task, whereas in older, free-flying bees, caffeine improves both motivation and cognitive performance in complex learning tasks. Our results suggest that the honeybee model may be useful in explaining caffeine-related behavioural changes not only in this species, but also in mammalian systems.

Animals↗

Jelleines: a family of antimicrobial peptides from the Royal Jelly of honeybees (Apis mellifera).

Four antimicrobial peptides were purified from Royal Jelly of honeybees, by using reverse phase-HPLC and sequenced by using Q-Tof-MS/MS: PFKLSLHL-NH(2) (Jelleine-I), TPFKLSLHL-NH(2) (Jelleine-II), EPFKLSLHL-NH(2) (Jelleine-III), and TPFKLSLH-NH(2) (Jelleine-IV). The peptides were synthesized on-solid phase, purified and submitted to different biological assays: antimicrobial activity, mast cell degranulating activity and hemolysis. The Jelleines-I-III presented exclusively antimicrobial activities against yeast, Gram+ and Gram- bacteria; meanwhile, Jelleine-IV was not active in none of the assays performed. These peptides do not present any similarity with the other antimicrobial peptides from the honeybees; they are produced constitutively by the workers and secreted into Royal Jelly.

Animals↗

Screening of biological activities present in honeybee (Apis mellifera) royal jelly.

Bioactivities present in three honeybee royal jelly (RJ) protein fractions were screened for diverse in vitro model systems. RJCP, a RJ crude protein extract, stimulated cell growth of Tn-5B1-4 insect cells inducing 6.5 population doublings per mg of protein added to culture medium, meanwhile fetal bovine serum, the usual growth supplement, gave rise only to 2.55 population doublings. RJCP, as well as the fractions RJP30 and RJP60 obtained by precipitation with ammonium sulfate, also affected Tn-5B1-4 cell shape and stimulated adhesion of these cells to the substrate. RJP30 also increased the percent of mature adipocytes in cultures of 3T3-F442A murine preadipocytes twofold with respect to insulin treatment, without inducing additional cell growth of confluent preadipocytes. Fractions RJCP and RJP60 showed similar capacity as that of insulin to stimulate the formation of mature 3T3 adipocytes. Fraction RJP30 also was cytotoxic for HeLa human cervicouterine carcinoma cells, diminishing 2.5-fold the initial cell density after seven days of treatment. Our results show the presence of diverse bioactivities in RJ affecting cell growth, cell differentiation and cell survival of insect, murine, and human cancer cells.

3T3 Cells↗