Dynamics of colony emigration in the ant Aphaenogaster senilis

In many social insect species, colonies frequently emigrate to a new nest. This requires the coordination of many individuals, and it puts the queen at risks of being lost or predated. We experimentally studied colony emigration in the ant Aphaenogaster senilis, who emigrates frequently and obligatorily reproduces by colony fission. As in other species, colony emigration was characterised by a synchronised relocation of workers. Foragers found the new nest site and triggered the relocation of the “inside” workers, which built up following a sigmoid curve. Unlike in Temnothorax, where workers are transported to the new nest, most individuals relocated by walking. The brood was transported around the middle of colony relocation, mostly by “inside” workers because they represent most of the workforce. The queen walked to the new nest at the middle of colony relocation, when the flow of ants to the new nest was maximal. Overall, this temporal dynamic of colony emigration is similar to that observed in other species. However, we argue that species-specific traits, such as whether workers are transported to the new nest or relocate by themselves, may affect parts of the process of colony emigration.     

Effect of primer pheromones and pollen diet on the food producing glands of worker honey bees (Apis mellifera L.)

Cooperative brood care is highly developed in the honey bee such that workers called nurses use their hypopharyngeal and mandibular glands to biosynthesize proteinaceous secretions that are progressively provisioned to larvae. The role that honey bee primer pheromones play in the functional physiology of food producing glands was examined. The combined and separate effects of queen mandibular pheromone (QMP) and brood pheromone (BP) on amount of protein extractable from hypopharyngeal and mandibular glands of workers reared for 12 days with and without pollen diets was measured. In rearing environments with a pollen diet, BP, and QMP + BP pheromone treatments significantly increased extractable protein from both glands. Bees reared with QMP + pollen had amounts of protein extractable from both glands that were not significantly different from control bees (no pheromones, no pollen). Pollen in the diet alone significantly increased amounts of protein extractable from glands versus control. In rearing environments without pollen, QMP + BP had a synergizing effect on amount of protein in both glands. The QMP + BP treatment was the only rearing environment without a pollen diet where protein amounts were significantly greater than the control. The synergizing effect of QMP + BP on extractable mandibular and hypopharyngeal gland protein suggests a highly derived role for the combined effect of these two primer pheromones on honey bee cooperative brood care. Mandibular gland area was significantly and positively correlated with extractable protein. Amounts of extractable protein from both glands declined significantly with age of workers in all treatments. However, treatment significantly affected rate of decline. The adaptive significance of gland protein amounts in response to pheromones and pollen diet are discussed.     

Pupal developmental temperature and behavioral specialization of honeybee workers (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Honeybees (Apis mellifera) are able to regulate the brood nest temperatures within a narrow range between 32 and 36°C. Yet this small variation in brood temperature is sufficient to cause significant differences in the behavior of adult bees. To study the consequences of variation in pupal developmental temperature we raised honeybee brood under controlled temperature conditions (32, 34.5, 36°C) and individually marked more than 4,400 bees, after emergence. We analyzed dancing, undertaking behavior, the age of first foraging flight, and forager task specialization of these workers. Animals raised under higher temperatures showed an increased probability to dance, foraged earlier in life, and were more often engaged in undertaking. Since the temperature profile in the brood nest may be an emergent property of the whole colony, we discuss how pupal developmental temperature can affect the overall organization of division of labor among the individuals in a self-organized process.     

西方蜜蜂幼虫发育温度对成体翅膀形态的影响

为探讨不同恒定温度条件对培育蜜蜂蛹翅膀形态特征的影响,作者将进入蛹期的西方蜜蜂(Apismellifera)放入人工气候箱里,分别在32、35和36℃的恒定温度条件培育,直到蜜蜂蛹羽化出房为止。测量了蜜蜂翅膀的标准形态特征,包括翅的大小、肘脉长和11个翅肘脉角,所得到的数据进行多变量比较分析、相关性分析、主成分分析和区别分析。研究结果表明,不同温度条件对蜜蜂翅膀形态特征有明显的影响     

Laying workers in queenless honeybee (Apis mellifera L.) colonies have physiological states similar to that of nurse bees but opposite that of foragers

Honeybee workers shift their labors from nursing their brood to foraging according to their age after eclosion. When the queen is lost from the colony, however, some workers become 'laying workers' whose ovaries develop to lay eggs. Here we investigated whether the physiological state of laying workers is more similar to that of nurse bees or foragers by examining the hypopharyngeal gland (HPG) and hemolymph vitellogenin titers. In a normal colony, nurse bees have well-developed HPGs that synthesize 'major royal jelly proteins' and high hemolymph vitellogenin titers, whereas foragers have shrunken HPGs that synthesize 70-kDa alpha-glucosidase and low hemolymph vitellogenin titers. In queenless colonies, however, workers with developed ovaries (laying workers) tended to have more developed HPGs and to synthesize major royal jelly proteins, whereas workers with shrunken HPGs tended to synthesize alpha-glucosidase and to have undeveloped ovaries. Furthermore, the workers with developed ovaries had higher vitellogenin titers than nurse bees, whereas those with undeveloped ovaries had lower vitellogenin titers. These findings indicate that the physiological state of laying workers is similar to that of nurse bees, but opposite that of foragers.     

Sucrose response thresholds of honey bee (Apis mellifera) foragers are not modulated by brood ester pheromone

Division of labor is a hallmark of eusocial insects and their ecological success can be attributed to it. Honey bee division of labor proceeds along a stereotypical ontogenetic path based on age, modulated by various internal and external stimuli. Brood pheromone is a major social pheromone of the honey bee that has been shown to affect honey bee division of labor. It elicits several physiological and behavioral responses; notably, regulating the timing of the switch from performing in-hive tasks to the initiation of foraging. Additionally, brood pheromone affects future foraging choice. In honey bees, sucrose response threshold is a physiological correlate of age of first foraging and foraging choice. Brood pheromone has been shown to modulate sucrose response threshold in young bees, but its effects on sucrose response thresholds of bees in advanced behavioral states (foragers) are not known. In this study we examined the sucrose response thresholds of two different task groups, foragers (pollen and non-pollen) and non-foraging bees, in response to honey bee brood pheromone. Sucrose response thresholds were not significantly different between brood pheromone treatment and controls among both non-pollen and pollen foragers. However, the sucrose response threshold of non-foraging bees was significantly higher in the brood pheromone treatment group than in the control group. The switch to foraging task is considered a terminal one, with honey bee lifespan being determined at least partially by risks and stress accompanying foraging. Our results indicate that foragers are physiologically resistant to brood pheromone priming of sucrose response thresholds.     

Vitamin e hypervitaminosis in laying hens

The aim of this investigation was to contribute to the problem of overdosing vitamin E. A total of 80 laying hens, divided into 5 groups, were fed diets supplemented with 0; 100, 1000, 10 000 and 20 000 mg/kg vitamin E over a period of 20 weeks within two brooding tests. Laying performance and hatching parameters were registered. All vitamin E doses did not significantly influence health and performances of hens. Vitamin E content of eggs increased from 1 to 4, 21, 46 and 51 mg per egg with vitamin E supplementation. High doses decreased oxidative stability of abdominal fat, vitamin A concentration of liver and egg yolk colour. In both tests vitamin E supplements of 10 000 and 20 000 mg/kg feed resulted in a decrease of living hatched chicken, which demonstrated an adverse effect. Further studies seem to be necessary to explain the effect.     

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.     

Photoperiod influences endogenous rhythm of ambient temperature selection by the honeybee Apis mellifera

The aim of this study was to evaluate whether the day–night cycle phase is a critical factor modulating diurnal rhythm of isolated honeybee's thermal preference or other factors are involved. The insects were exposed to standard (LD 12:12) and reversed (DL 12:12) photoperiods as well as to constant light and constant darkness conditions. Thermal preference and motor activity of honeybees were recorded for 3–5 days in a thermal gradient system. Under the standard (control) photoperiod conditions mean values of temperature selected by honeybees changed rhythmically within the period of about 24 h. Honeybees, exposed to the modified light–darkness cycle distinctly modified their rhythm of thermal preference. Under the reversed photoperiod conditions period of selected ambient temperature was much longer than before, until a complete reversal of the circadian oscillation was established at the end of the experiment. Experiments performed under constant light and constant darkness yielded undisturbed 24 h rhythms of both ambient temperature selection and locomotor activity. Under these conditions only a slight, nonsignificant flattening of the temperature selection curves was noticed. Both lack of substantial changes in the amplitude and occurring phase shifts of the rhythm, recorded in our experiments suggest its endogenous character. Our results prove that diurnal rhythm of ambient temperature selection by bee workers may be entrained by light–dark cycles. This implies a critical role of photoperiod in the modulation of nychthemeral oscillations of thermal preference in honeybees.     

Higher vitellogenin concentrations in honey bee workers may be an adaptation to life in temperate climates

The honey bee originated in tropical Africa and later dispersed to northern Europe. It has been suggested that a higher hemolymph storage capacity for the glycolipoprotein vitellogenin evolved in temperate regions, and that the trait constitutes an adaptation to a strongly seasonal environment. We have investigated whether the relative vitellogenin levels of European and African honey bees are in accordance with this hypothesis. Our data indicate that European workers have a higher set-point concentration for vitellogenin compared to their African origin. Considered together with available life history information and physiological data, the results lend support to the view that “winter bees”, a longlived honey bee worker caste that survives winter in temperate regions, evolved through an increase in the worker bees’ capacity for vitellogenin accumulation. Received 20 September 2004; revised 25 March 2005; accepted 13 April 2005.     

Hygropreference and brood care in the honeybee (Apis mellifera)

Terrestrial organisms need to limit evaporation from their bodies in order to maintain a homeostatic water balance. Owing to a large surface to volume ratio, arthropods are particularly susceptible to desiccation and have evolved behavioural and physiological mechanisms to conserve water. In social insects, water balance is also affected by the interactions between nestmates and by the architecture of the nest. For honeybees, humidity is particularly important for the brood because it affects the hatching success of eggs and because, unlike ants, honeybees cannot relocate their brood to parts of the nest with more favourable humidity. To advance the understanding of the water economy in honeybee nests, we investigated whether workers exhibit a hygropreference when exposed to a gradient of 24-90% relative humidity (RH) and whether the expression of this preference and their behaviour is affected by the presence of brood. The results show that young honeybee workers in the absence of brood exhibit a weak hygropreference for approximately 75% RH. When brood is present the expression of this preference is further weakened, suggesting that workers tend to the brood by distributing evenly in the gradient. In addition, fanning behaviour is shown to be triggered by an increase in humidity above the preferred level but not by a decrease. Our results suggest that humidity in honeybee colonies is actively controlled by workers.