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PubMed2003

Hot bees in empty broodnest cells: heating from within.

Honeybee colonies maintain brood nest temperatures of 33-36 degrees C. We investigated brood nest thermoregulation at the level of individual worker behaviour and the transfer of heat from workers to the brood. Worker bees contribute to the regulation of brood nest temperature by producing heat while sitting motionless on the caps of brood cells. We report here an additional, newly observed heating strategy where heating bees enter empty cells between sealed brood cells and remain there motionless for periods of up to 45 min. Individually marked worker bees on the surface of sealed brood cells maintained thorax temperatures (T(th)) between 32.2+/-1.0 degrees C and 38.1+/-2.5 degrees C (mean +/- S.D.; N=20 bees) with alternating warming and cooling periods. Most of the observed bees made one or several long-duration visits (>2 min) to empty cells within the sealed brood area. T(th) at the time bees entered a cell [T(th(entry))] was 34.1-42.5 degrees C (N=40). In 83% of these cell visits, T(th(entry)) was higher (up to 5.9 degrees C; mean 2.5+/-1.5 degrees C; N=33) than the mean T(th) of the same bee. High values of T(th(entry)) resulted from preceding heating activity on the comb surface and from warm-ups just prior to cell visits during which T(th) increased by up to +9.6 degrees C. Bees inside empty cells had mean T(th) values of 32.7+/-0.1 degrees C (resting bees) to 40.6+/-0.7 degrees C (heat-producing bees) during long-duration cell visits without performing any visible work. Heating behaviour inside cells resembles heating behaviour on the brood cap surface in that the bees appear to be inactive, but repeated warmings and coolings occur and T(th) does not fall below the optimum brood temperature. Bees staying still inside empty cells for several minutes have previously been considered to be 'resting bees'. We find, however, that the heating bees can be distinguished from the resting bees not only by their higher body temperatures but also by the continuous, rapid respiratory movements of their abdomens. By contrast, abdominal pumping movements in resting bees are discontinuous and interrupted by long pauses. Heat transfer to the brood from individual bees on the comb surface and from bees inside empty cells was simulated under controlled conditions. Heating on the comb surface causes a strong superficial warming of the brood cap by up to 3 degrees C within 30 min. Heat transfer is 1.9-2.6 times more efficient when the thorax is in touch with the brood cap than when it is not. Heating inside empty cells raises the brood temperature of adjacent cells by up to 2.5 degrees C within 30 min. Heat flow through the comb was detectable up to three brood cells away from the heated thorax.

Animals↗
PubMed1995

Effects of experience and juvenile hormone on the organization of the mushroom bodies of honey bees.

There is an age-related division of labor in the honey bee colony that is regulated by juvenile hormone. After completing metamorphosis, young workers have low titers of juvenile hormone and spend the first several weeks of their adult lives performing tasks within the hive. Older workers, approximately 3 weeks of age, have high titers of juvenile hormone and forage outside the hive for nectar and pollen. We have previously reported that changes in the volume of the mushroom bodies of the honey bee brain are temporally associated with the performance of foraging. The neuropil of the mushroom bodies is increased in volume, whereas the volume occupied by the somata of the Kenyon cells is significantly decreased in foragers relative to younger workers. To study the effect of flight experience and juvenile hormone on these changes within the mushroom bodies, young worker bees were treated with the juvenile hormone analog methoprene but a subset was prevented from foraging (big back bees). Stereological volume estimates revealed that, regardless of foraging experience, bees treated with methoprene had a significantly larger volume of neuropil in the mushroom bodies and a significantly smaller Kenyon cell somal region volume than did 1-day-old bees. The bees treated with methoprene did not differ on these volume estimates from untreated foragers (presumed to have high endogenous levels of juvenile hormone) of the same age sampled from the same colony. Bees prevented from flying and foraging nonetheless received visual stimulation as they gathered at the hive entrance. These results, coupled with a subregional analysis of the neuropil, suggest a potentially important role of visual stimulation, possibly interacting with juvenile hormone, as an organizer of the mushroom bodies. In an independent study, the brains of worker bees in which the transition to foraging was delayed (overaged nurse bees) were also studied. The mushroom bodies of overaged nurse bees had a Kenyon cell somal region volume typical of normal aged nurse bees. However, they displayed a significantly expanded neuropil relative to normal aged nurse bees. Analysis of the big back bees demonstrates that certain aspects of adult brain plasticity associated with foraging can be displayed by worker bees treated with methoprene independent of foraging experience. Analysis of the overaged nurse bees suggests that the post-metamorphic expansion of the neuropil of the mushroom bodies of worker honey bees is not a result of foraging experience.

Aging↗
PubMed2003

Honey bee (Hymenoptera: Apidae) pollination of rabbiteye blueberry Vaccinium ashei var. 'Climax' is pollinator density-dependent.

In a 2-yr field study, mature orchard plants of rabbiteye blueberry (Vaccinium ashei Reade variety 'Climax'), plus potted pollenizers ('Premier') were caged with varying densities of honey bees (0, 400, 800, 1,600, 3,200, 6,400, or 12,800 bees plus open plot) during the bloom interval. The rate of legitimate flower visits tended to increase as bee density increased within a range of 400-6,400 bees; there were more legitimate visits in cages with 6,400 bees than in those with < or = 1,600 bees. Similarly, within a range of 400-6,400 bees there was a trend for a corresponding increase in fruit-set with means ranging from 25.0 to 79%. Fruit-set was higher in cages with 6,400 or 3,200 bees than in those with < or = 800 bees. Regression analyses showed that fruit-set increased linearly with the rate of legitimate bee visits. Mean weight of berries was unaffected by bee density but varied significantly between years. Within a range of 0-3,200 bees/cage the average seeds per berry tended to increase with increasing bee density; there were more seeds in open plots than in cages with 12,800 honey bees or < or = 1,600 bees. Sucrose content ranged from 12.1 to 16.7% and fruits tended to have more sugar in cages with lower bee densities. Speed of ripening tended to be higher in cages with higher bee densities. Earlier work has shown that the effectiveness of Apis mellifera L. as a pollinator of rabbiteye blueberry is variety-dependent. Our data indicate that the effectiveness of A. mellifera is also bee density-dependent.

Animals↗
PubMed2004

Honey bee (Hymenoptera: Apidae) distribution and potential for supplementary pollination in commercial tomato greenhouses during winter.

This study examined the use of honey bees, Apis mellifera L., to supplement bumble bee, Bombus spp., pollination in commercial tomato, Lycopersicon esculentum Miller, greenhouses in Western Canada. Honey bee colonies were brought into greenhouses already containing bumble bees and left for 1 wk to acclimatize. The following week, counts of honey and bumble bees foraging and flying throughout the greenhouse were conducted three times per day, and tomato flowers open during honey bee pollination were marked for later fruit harvest. The same counts and flower-marking also were done before and after the presence of honey bees to determine the background level of bumble bee pollination. Overall, tomato size was not affected by the addition of honey bees, but in one greenhouse significantly larger tomatoes were produced with honey bees present compared with bumble bees alone. In that greenhouse, honey bee foraging was greater than in the other greenhouses. Honey bees generally foraged within 100 m of their colony in all greenhouses. Our study invites further research to examine the use of honey bees with reduced levels of bumble bees, or as sole pollinators of greenhouse tomatoes. We also make specific recommendations for how honey bees can best be managed in greenhouses.

Agriculture↗
PubMed2004

Influence of brood, vent screening, and time of year on honey bee (Hymenoptera: Apidae) pollination and fruit quality of greenhouse tomatoes.

Greenhouse tomatoes, Lycopersicon esculentum Miller (Solanaceae), are autogamous, but facilitated pollination results in increased fruit size and set. Previous research examining honey bee pollination in greenhouse tomato crops established that fruit quality resulting from honey bee visitation is often comparable to bumble bees (Bombus spp.) and significantly better than in flowers that receive no facilitated pollination. However, management alternatives have not been studied to improve tomato fruit quality when honey bees are the only pollination option available for the high-value greenhouse industry. We investigated whether the quantity of brood (eggs, larvae, and pupae) in a honey bee colony in the winter and screening on greenhouse vents in the summer would encourage honey bee foraging on tomato flowers. We also established the influence of time of year on the potential for honey bees to be effective pollinating agents. We constructed small honey bee colonies full of naive forager bees with either two frames of brood ("brood colonies") or two empty frames ("no-brood") and compared total fruit set and the number of tomato seeds resulting from fruit potentially visited by honey bees in each of these treatments to bagged flowers that received no facilitated pollination. There was no significant difference in the quality of fruit resulting from honey bees from "brood" and "no-brood" colonies. However, these fruits produced significantly more seeds than bagged flowers restricted from facilitated pollination. Honey bees from brood and no-brood colonies also resulted in 98% fruit set compared with 80% fruit set in bagged flowers that received no facilitated pollination. During the summer, the number of seeds per fruit did not differ significantly between unbagged flowers potentially visited by honey bees in screened greenhouses and unscreened greenhouses and bagged flowers that received no facilitated pollination. However, time of year did have a significant influence on the quality of fruit produced by honey bees compared with flowers that received no facilitated pollination, because no difference in seed number was observed between the treatments after mid-April. The results from this study demonstrate that the management of brood levels and vent screening cannot be used to improve the quality of fruit resulting from honey bee pollination and that honey bees can be a feasible greenhouse pollination alternative only during the winter.

Agriculture↗
PubMed1990

Quantity, analysis, and lethality of European and Africanized honey bee venoms.

Venom from Africanized honey bees (derived mainly from Apis mellifera scutellata) was compared with venom from domestic, European bees by study of lethality, immunological cross-reactivity, venom yield, isoelectric focusing (IEF) patterns, and melittin titers. The LD50s of European and Africanized bee venom by iv injection in mice were similar. In venom neutralization experiments, Africanized bee venom was mixed with antibodies from a beekeeper exposed only to European bees and used to challenge mice. Survival times of mice given these mixtures were significantly prolonged, indicating that human serum antibodies to European bee venom neutralized the lethal effects of Africanized bee venom. Reservoirs from Africanized bees contained less venom than European bees (94 and 147 micrograms venom/bee, respectively) and Africanized bee venom had a lower melittin content. The IEF patterns of venom from individual European bees varied considerably, as did IEF patterns of individual Africanized bees. Pools of venom from 1,000 bees of each population of A. mellifera showed noticeable but less obvious electrophoretic differences. The findings suggest that multiple stinging, and not increased venom potency or delivery, is the cause of serious reactions from Africanized bee attacks.

Africa↗
PubMed2003

Behavioral performance in adult honey bees is influenced by the temperature experienced during their pupal development.

To investigate the possible consequences of brood-temperature regulation in honey bee colonies on the quality of behavioral performance of adults, we placed honey bee pupae in incubators and allowed them to develop at temperatures held constant at 32 degrees C, 34.5 degrees C, and 36 degrees C. This temperature range occurs naturally within hives. On emergence, the young adult bees were marked and introduced into foster colonies housed in normal and observation hives and allowed to live out their lives. No obvious difference in within-hive behavior was noted between the temperature-treated bees and the foster-colony bees. However, when the temperature-treated bees became foragers and were trained to visit a feeder 200 m from the hive, they exhibited clear differences in dance performance that could be correlated with the temperatures at which they had been raised: bees raised at 32 degrees C completed only approximately 20% of the dance circuits when compared with bees of the higher-temperature group. Also, the variance in the duration of the waggle phase is larger in 32 degrees C-raised bees compared with 36 degrees C-raised bees. All other parameters compared across all groups were not significantly different. One-trial learning and memory consolidation in the bees raised at different temperatures was investigated 1 and 10 min after conditioning the proboscis-extension reflex. Bees raised at 36 degrees C performed as expected for bees typically classified as "good learners," whereas bees raised at 32 degrees C and 34.5 degrees C performed significantly less well. We propose that the temperature at which pupae are raised will influence their behavioral performance as adults and may determine the tasks they carry out best inside and outside the hive.

Animals↗
PubMed2000

Phospholipase A2-induced coagulation abnormalities after bee sting.

We will examine the correlation between various bee venom phospholipase A2 (PLA2) concentrations and several parameters of coagulation in human plasma in order to offer a rationale for requesting a particular laboratory coagulation test after bee sting(s). We will also evaluate in vitro the influence of clinically available drugs with a noncompetitive inhibitory effect on PLA2 on the anticoagulant effect of bee venom PLA2. Prothrombin index (PTi), partial thromboplastin time (PTT), antithrombin III (AT III), soluble fibrin monomers (SFM), the activity of coagulation factors I, II, V, and VIII, and thrombelastography (TEG) parameters (split point [Sp], reaction time [R], kinetic time [K], coagulation time [R + K], maximal amplitude [MA], and the growth angle [alpha]) were determined before and after addition of 1.4, 2.7, and 4.1 units (1, 2, and 3 microg protein respectively) of bee venom PLA2. Linear regression was used to determine the significance of the relationship between these coagulation parameters and bee venom PLA2 concentrations used. To study the influence of ketamine, lidocaine, magnesium, furosemide, and cromolyn on the anticoagulant effect of bee venom PLA2, PTi and factor II- and V-activities were measured before and after addition of 2.7 units of PLA2 and PLA2 plus one of the tested substances. Determinations of F II, PTi, F V, and F VIII showed a negative correlation to bee venom PLA2 concentration (r = -0.88, -0.86, -0.81, and -0.79 respectively). A positive correlation was found for PTT (r = 0.69). FII- activity and PTi correlated better with bee venom PLA2 concentration than other parameters. F I, AT III, and SFM showed no changes. Whereas Sp, R, and K were prolonged by bee venom PLA2 and a was reduced, there was no correlation to the PLA2 concentration. Addition of none of the 5 substances could correct the effects of bee venom PLA2 on the coagulation. In a patient with toxic reaction or a severe anaphylactic reaction after bee sting(s) we suggest determinations of FII and/or PTi. This will allow a quick and economical assessment of coagulation abnormalities after bee sting(s). Noncompetitive PLA2-inhibitors (ketamine, lidocaine, magnesium, furosemide, and cromolyn) are unable to correct in vitro the anticoagulant effect of bee venom PLA2. They cannot be recommended at this stage for this purpose. Further investigations with competitive PLA2-inhibitors are warranted.

Animals↗
PubMed2001

Comparative study of the venoms from three species of bees: effects on heart activity and blood.

Crude venoms from three highly evolved aculeate species: Apis mellifera (highly social bees), Bombus morrisoni (eusocial bees), and Anthophora pauperata (solitary bees), were used for conducting this study to compare the effects of honey bee, bumble bee, and solitary bee venom on toad cardiac muscle activity. In addition, these venoms were tested on rat whole blood in order to determine their ability to induce red blood cell haemolysis. The main toxic effects on isolated toad heart were monitored by ECG after perfusion with different concentrations of each bee venom, and are represented as a decrease in the heart rate (HR) accompanied by an elongation in the P-R interval. A gradual and progressive increase in R-wave amplitude was also noted. Several electrocardiographic changes were noted 5-30 min after envenomation with any of the bee venoms. The mechanism of action of the three bee venoms was determined by direct application of atropine, nicotine, or verapamil to the isolated toad hearts. Comparison of the three venoms revealed that Anthophora pauperata venom is the most effective venom in inducing bradycardia, and it has the strongest negative dromotropic effect. Apis mellifera venom demonstrates the most positive inotropic effect of the three venoms. The effects of bee venom on the blood indices of erythrocyte osmotic fragility (EOF) and plasma albumin levels were studied after incubation of rat blood with each venom. It was noticed that RBCs decreased while Hb content, HCT, MCV, MCH, and MCHC increased, although this change did fluctuate and was not significant. A nonsignificant decrease in EOF was noted after 60 min with any of the venoms used. Incubation of rat whole blood with 1 microg/ml of any of the bee venom solutions revealed a highly significant decrease in plasma albumin levels. It can be concluded that venoms from the three species of bees we tested have negative chronotropic and dromotropic effects on isolated toad heart, with Anthophora pauperata being the most potent. In addition, the venoms have positive inotropic effects withApis mellifera being the most potent. The nonsignificant effects of venom on blood profiles and erythrocyte osmotic fragility, combined with the significant decrease in plasma albumin level suggest a protective effect of plasma albumin against bee venom induced toxicity to erythrocytes.

Animals↗