Hot spots in the bee hive

Honeybee colonies (Apis mellifera) maintain temperatures of 35-36°C in their brood nest because the brood needs high and constant temperature conditions for optimal development. We show that incubation of the brood at the level of individual honeybees is done by worker bees performing a particular and not yet specified behaviour: such bees raise the brood temperature by pressing their warm thoraces firmly onto caps under which the pupae develop. The bees stay motionless in a characteristic posture and have significantly higher thoracic temperatures than bees not assuming this posture in the brood area. The surface of the brood caps against which warm bees had pressed their thorax were up to 3.2°C warmer than the surrounding area, confirming that effective thermal transfer had taken place.     

Oviposition by small hive beetles elicits hygienic responses from Cape honeybees

Two novel behaviours, both adaptations of small hive beetles (Aethina tumida Murray) and Cape honeybees (Apis mellifera capensis Esch.), are described. Beetles puncture the sides of empty cells and oviposit under the pupae in adjoining cells. However, bees detect this ruse and remove infested brood (hygienic behaviour), even under such well-disguised conditions. Indeed, bees removed 91% of treatment brood (brood cells with punctured walls caused by beetles) but only 2% of control brood (brood not exposed to beetles). Only 91% of treatment brood actually contained beetle eggs; the data therefore suggest that bees remove only that brood containing beetle eggs and leave uninfected brood alone, even if beetles have accessed (but not oviposited on) the brood. Although this unique oviposition strategy by beetles appears both elusive and adaptive, Cape honeybees are able to detect and remove virtually all of the infested brood.     

Aggressive behavior of the male parent predicts brood sex ratio in a songbird

Brood sex ratio is often affected by parental or environmental quality, presumably in an adaptive manner that is the sex that confers higher fitness benefits to the mother is overproduced. So far, studies on the role of parental quality have focused on parental morphology and attractiveness. However, another aspect, the partner’s behavioral characteristics, may also be expected to play a role in brood sex ratio adjustment. To test this hypothesis, we investigated whether the proportion of sons in the brood is predicted by the level of territorial aggression displayed by the father, in the collared flycatcher (Ficedula albicollis). The proportion of sons in the brood was higher in early broods and increased with paternal tarsus length. When controlling for breeding date and body size, we found a higher proportion of sons in the brood of less aggressive fathers. Male nestlings are more sensitive to the rearing environment, and the behavior of courting males may often be used by females to assess their future parental activity. Therefore, adjusting brood sex ratio to the level of male aggression could be adaptive. Our results indicate that the behavior of the partner could indeed be a significant determinant in brood sex ratio adjustment, which should not be overlooked in future studies.     

Caps and gaps: a computer model for studies on brood incubation strategies in honeybees (<Emphasis Type="Italic">Apis mellifera carnica</Emphasis>)

In addition to heat production on the comb surface, honeybee workers frequently visit open cells (“gaps”) that are scattered throughout the sealed brood area, and enter them to incubate adjacent brood cells. We examined the efficiency of this heating strategy under different environmental conditions and for gap proportions from 0 to 50%. For gap proportions from 4 to 10%, which are common to healthy colonies, we find a significant reduction in the incubation time per brood cell to maintain the correct temperature. The savings make up 18 to 37% of the time, which would be required for this task in completely sealed brood areas without any gaps. For unnatural high proportions of gaps (>20%), which may be the result of inbreeding or indicate a poor condition of the colony, brood nest thermoregulation becomes less efficient, and the incubation time per brood cell has to increase to maintain breeding temperature. Although the presence of gaps is not essential to maintain an optimal brood nest temperature, a small number of gaps make heating more economical by reducing the time and energy that must be spent on this vital task. As the benefit depends on the availability, spatial distribution and usage of gaps by the bees, further studies need to show the extent to which these results apply to real colonies. M. Fehler and M. Kleinhenz contributed equally to this work.     

Keeping eggs warm: thermal and developmental advantages for parasitic cuckoos of laying unusually thick-shelled eggs

Obligate brood parasites have evolved unusually thick-shelled eggs, which are hypothesized to possess a variety of functions such as resistance to puncture ejection by their hosts. In this study, we tested the hypothesis that obligate brood parasites lay unusually thick-shelled eggs to retain more heat for the developing embryo and thus contribute to early hatching of parasite eggs. By doing so, we used an infrared thermal imaging system as a non-invasive method to quantify the temperature of eggshells of common cuckoos (Cuculus canorus) and their Oriental reed warbler (Acrocephalus orientalis) hosts in an experiment that artificially altered the duration of incubation. Our results showed that cuckoo eggshells had higher temperature than host eggs during incubation, but also less fluctuations in temperature during incubation disturbance. Therefore, there was a thermal and hence a developmental advantage for brood parasitic cuckoos of laying thick-shelled eggs, providing another possible explanation for the unusually thick-shelled eggs of obligate brood parasites and earlier hatching of cuckoo eggs compared to those of the host.     

Out with the garbage: the parasitic strategy of the mantisfly Plega hagenella mass-infesting colonies of the eusocial bee Melipona subnitida in northeastern Brazil

Between April and June of 2012 mantisflies (Plega hagenella) were found to be extensively parasitizing the nests of two groups of managed colonzies of eusocial stingless bees (Melipona subnitida) in the semi-arid region of northeastern Brazil. The mantisfly larvae developed inside closed brood cells of the bee comb, where each mantispid larva fed on the bee larva or pupa present in a single brood cell. Mature mantispid larvae pupated inside silken cocoons spun in place within their hosts' brood cells then emerged as pharate adults inside the bee colony. Pharate adults were never attacked and killed by host colony workers. Instead, colony workers picked up the pharates and removed them from the nest unharmed, treating them similar to the way that the general refuse is removed from the nest. Adult mantispids subsequently eclosed from their pupal exuviae outside the nest. Manipulative experiments showed that post-eclosion adult mantispids placed back within active bee colonies were quickly attacked and killed. These observations demonstrate that pharate and post-eclosion adults of P. hagenella are perceived differently by colony workers and that delayed adult eclosion is an important functional element in the parasitic life strategy of P. hagenella, allowing adults to escape without injury from the bee colonies they parasitize.     

Effects of cross-feeding anarchistic and wild type honey bees: anarchistic workers are not queen-like

Unlike normal (wild type) honey bee ( Apis mellifera) colonies, 'anarchistic' colonies are characterised by workers that activate their ovaries in the presence of the queen and brood and by the ability of their workers to lay eggs that evade worker policing. In the Cape honey bee ( A. m. capensis), female larvae can manipulate non- capensis nurse workers such that they receive more larval food and develop into worker-queen intermediates or intercastes. We speculated that, in anarchistic colonies, larvae might produce signals that result in excessive feeding of female larvae. Excessively fed female larvae may then develop into reproductively active workers. In this study we cross-fostered anarchistic and wild type brood and investigated the effect of cross-fostering on the amount of food fed to larvae and on the morphology of the resulting workers. We show that anarchistic larvae do not manipulate wild type nurse workers into feeding them more, nor do anarchistic workers develop into worker-queen intermediates. On the contrary, anarchistic larvae are fed less than wild type larvae and anarchistic workers seem to be poor nurses in that they feed larvae less, irrespective of brood genotype.     

Does the Spatial Distribution of the Parasitic Mite Varroa jacobsoni Oud. (Mesostigmata: Varroidae) in Worker Brood of Honey Bee Apis Mellifera L. (Hymenoptera: Apidae) Rely on an Aggregative Process?

  Varroa jacobsoni is an ectoparasite of honey bees which reproduces in capped brood cells. Multi-infestation is frequently observed in worker brood and can be interpreted as an aggregative phenomenon. The aim of this study was to determine whether the distribution of V. jacobsoni in worker brood cells relies on a random or an aggregative process. We studied the distribution of Varroa females in capped worker brood at similar age by comparing, by a Monte Carlo test, the observed frequency distribution of mites per cell to simulated distributions based on a random process. A complementary approach, using the "nearest neighbor distances" (NND) with Monte Carlo tests, was investigated to study the spatial distribution (a) between mites in different cells and (b) between infested cells in brood. The observed distributions did not differ significantly from that expected by a random process, and we conclude that there is no aggregation during invasion of V. jacobsoni in worker brood. Received: 29 April 1999 / Accepted in revised form: 26 August 1999     

Disc size regulation in the brood cell building behavior of leaf-cutter bee, <Emphasis Type="Italic">Megachile tsurugensis</Emphasis>

The leaf-cutter bee, Megachile tsurugensis, builds a brood cell in a preexisting tunnel with leaf discs that she cuts in decreasing sizes and assembles them like a Russian matryoshka doll. By experimentally manipulating the brood cell, it was investigated how she regulates the size of leaf discs that fit in the brood cell’s internal volume. When the internal volume was artificially increased by removing a bulk of leaf discs, she decreased the leaf disc size, although increasing it would have made the leaf disc more fitting in the increased internal volume. As a reverse manipulation, when the internal volume was decreased by inserting a group of inner layers of preassembled leaf discs to a brood cell, she decreased the leaf disc size, so that the leaf disc could fit in the decreased internal volume. These results suggest that she uses at least two different mechanisms to regulate the disc size: the use of some internal memory about the degree of building work accomplished in the first and of sensory feedback of dimensional information at the construction site in the second manipulation, respectively. It was concluded that a stigmergic mechanism, an immediate sensory feedback from the brood cell changed by the building work, alone cannot explain the details of the bee’s behavior particularly with respect to her initial response to the first manipulation. For a more complete explanation of the behavior exhibited by the solitary bee, two additional behavioral elements, reinforcement of building activity and processing of dimensional information, were discussed along with stigmergy.     

Using the nematode Caenorhabditis elegans as a model animal for assessing the toxicity induced by microcystin-LR

Among more than 75 variants of microcystin(MC),microcystin-LR(MC-LR) is one of the most common toxins.In this study,the feasibility of using Caenorhabditis elegans to evaluate MC-LR toxicity was studied.C.elegans was treated with MC-LR at different concentrations ranging from 0.1 to 80 μg/L.The results showed that MC-LR could reduce lifespan,delay development,lengthen generation time,decrease brood size,suppress locomotion behavior,and decreases hsp-16-2-gfp expression.The endpoints of generation time,brood...     

Heat Shielding: A Novel Method of Colonial Thermoregulation in Honey Bees

 Honey bees, Apis mellifera, maintain constant colony temperatures throughout the year. Honey bees fan their wings to cool the colony, and often spread fluid in conjunction with this behavior to induce evaporative cooling. We present an additional, previously undescribed mechanism used by the honey bee to maintain constant colony temperature in response to localized temperature increases. Worker bees shield the comb from external heat sources by positioning themselves on hot interior regions of the hive's walls. Although honey comb and brood comb were both shielded, the temperature-sensitive brood received a greater number of heat shielders and was thus better protected from overheating. Heat shielding appears to be a context-dependent adaptive behavior performed by worker bees who would previously have been considered "unemployed." Received: 16 November 1998 / Accepted in revised form: 31 March 1999     

Vasculature of the hive: heat dissipation in the honey bee (Apis mellifera) hive

Eusocial insects are distinguished by their elaborate cooperative behavior and are sometimes defined as superorganisms. As a nest-bound superorganism, individuals work together to maintain favorable nest conditions. Residing in temperate environments, honey bees (Apis mellifera) work especially hard to maintain brood comb temperature between 32 and 36 °C. Heat shielding is a social homeostatic mechanism employed to combat local heat stress. Workers press the ventral side of their bodies against heated surfaces, absorb heat, and thus protect developing brood. While the absorption of heat has been characterized, the dissipation of absorbed heat has not. Our study characterized both how effectively worker bees absorb heat during heat shielding, and where worker bees dissipate absorbed heat. Hives were experimentally heated for 15 min during which internal temperatures and heat shielder counts were taken. Once the heat source was removed, hives were photographed with a thermal imaging camera for 15 min. Thermal images allowed for spatial tracking of heat flow as cooling occurred. Data indicate that honey bee workers collectively minimize heat gain during heating and accelerate heat loss during cooling. Thermal images show that heated areas temporarily increase in size in all directions and then rapidly decrease to safe levels (<37 °C). As such, heat shielding is reminiscent of bioheat removal via the cardiovascular system of mammals.     

Spatial separation from family in the mobile young of a biparental fish: risks and dynamics of returning home

In species with extended parental care, mobile dependent young are potentially more vulnerable to predators when they stray and become separated from their parents. We would expect that the likelihood of, and latency time for, a separated young to safely return to its ‘family unit’ (i.e. parents and brood mates) to be, respectively, inversely and positively related to the initial distance of separation and potentially mediated by its age or body size. Using the biparental convict cichlid fish (Amatitlania siquia), we tested these predictions by capturing individual young and displacing them at varying distances from their family unit in both the field and laboratory. As expected, displaced fish were less likely, and took longer, to return to their family with increasing separation distance from the family unit. The body length of displaced young mediated these relationships and their antipredator behaviour; larger young refuged more than smaller ones and were also less likely to be eaten by predators. These results suggest that selection should favour strong affiliative behaviour in mobile young animals towards their brood mates and protective parents because straying from the family unit leads to increased exposure to predation and a reduced likelihood of returning home with increasing separation distance.     

Pheromone-modulated behavioral suites influence colony growth in the honey bee (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

The success of a species depends on its ability to assess its environment and to decide accordingly which behaviors are most appropriate. Many animal species, from bacteria to mammals, are able to communicate using interspecies chemicals called pheromones. In addition to exerting physiological effects on individuals, for social species, pheromones communicate group social structure. Communication of social structure is important to social insects for the allocation of its working members into coordinated suites of behaviors. We tested effects of long-term treatment with brood pheromone on suites of honey bee brood rearing and foraging behaviors. Pheromone-treated colonies reared significantly greater brood areas and more adults than controls, while amounts of stored pollen and honey remained statistically similar. Brood pheromone increased the number of pollen foragers and the pollen load weights they returned. It appeared that the pheromone-induced increase in pollen intake was directly canalized into more brood rearing. A two-way pheromone priming effect was observed, such that some workers from the same age cohorts showed an increased and extended capacity to rear larvae, while others were recruited at significantly younger ages into pollen-specific foraging. Brood pheromone affected suites of nursing and foraging behaviors allocating worker and pollen resources associated with an important fitness trait, colony growth.     

Explaining postnatal growth plasticity in a generalist brood parasite

Selection of a particular host has clear consequences for the performance of avian brood parasites. Experimental studies showed that growth rate and fledging mass of brood parasites varied between host species independently of the original host species. Finding correlates of this phenotypic plasticity in growth is important for assessing adaptiveness and potential fitness consequences of host choice. Here, I analyzed the effects of several host characteristics on growth rate and fledging mass of the young of brown-headed cowbird (Molothrus ater), a generalist, non-evicting brood parasite. Cowbird chicks grew better in fast-developing host species and reached higher fledging mass in large hosts with fast postnatal development. A potential proximate mechanism linking fast growth and high fledging mass of cowbird with fast host development is superior food supply in fast-developing foster species. So far, we know very little about the consequences of the great plasticity in cowbird growth for later performance of the adult parasite. Thus, cowbird species could become interesting model systems for investigating the role of plasticity and optimization in the evolution of growth rate in birds.     

渤海湾海丰盐场卤虫种类组成与生殖特性

1999年7～10月对渤海湾海丰盐场卤虫自然种群的种类组成和生殖特性进行了研究，结果表明：(1)原来仅有孤雌生殖种群，如今孤雌生殖卤虫与两性生殖卤虫Artemia franciscana共存，且在8～10月份外来种A.franciscana占主要部分。(2)温度是影响休眠卵产生的重要环境因子。实验期间温度降低，卵生比例升高，到9、10月份已全部为卵生。(3)随温度降低，怀后代数有上升的趋势。多数月份卤虫怀后代数与盐度负相关。     

Larval salivary glands are a source of primer and releaser pheromone in honey bee (Apis mellifera L.)

A brood pheromone identified in honeybee larvae has primer and releaser pheromone effects on adult bees. Using gas chromatography–mass spectrometry (GC–MS) to evaluate fatty acid esters—the pheromonal compounds—in different parts of the larvae, we have localized the source of the esters as the larval salivary glands. A histochemical study describes the glands and confirms the presence of lipids in the glands. Epithelial cells of the gland likely secrete the fatty acids into the lumen of the gland. These results demonstrate the salivary glands to be a reservoir of esters, components of brood pheromone, in honeybee larvae.     

Decision rules for egg recognition are related to functional roles and chemical cues in the queenless ant Dinoponera quadriceps

The capacity to distinguish colony members from strangers is a key component in social life. In social insects, this extends to the brood and involves discrimination of queen eggs. Chemical substances communicate colony affiliation for both adults and brood; thus, in theory, all colony members should be able to recognize fellow nestmates. In this study, we investigate the ability of Dinoponera quadriceps workers to discriminate nestmate and non-nestmate eggs based on cuticular hydrocarbon composition. We analyzed whether cuticular hydrocarbons present on the eggs provide cues of discrimination. The results show that egg recognition in D. quadriceps is related to both age and the functional role of workers. Brood care workers were able to distinguish nestmate from non-nestmate eggs, while callow and forager workers were unable to do so. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Colony size affects division of labour in the ponerine ant<Emphasis Type="Italic"> Rhytidoponera metallica</Emphasis>

In theory, larger colonies of social insects should have greater colony organisation. While inter-specific comparative studies provide support for this idea, there is little direct intra-specific evidence. We investigated differences in task specialisation between large (>450 workers) and small (<80 workers) colonies of the ponerine ant Rhytidoponera metallica. Observations of individually marked young or old workers revealed greater task specialisation in large colonies. Age polyethism was detected in large but not small colonies. In large colonies, old workers spent significantly more time foraging than young workers did, while young workers spent more time caring for brood. In small colonies, young and old workers spent a similar amount of time foraging and caring for brood. This difference in task allocation patterns in large and small colonies was associated with a difference in contact rates between workers. Workers in small colonies have a lower contact rate between nestmates and a greater variability in time between contacts than workers from large colonies.     

Seven suggestive quantitative trait loci influence hygienic behavior of honey bees

In 1964, Walter Rothenbuhler proposed a two-gene model to explain phenotypic variance in the remarkable behavior in which honey bee workers remove dead brood from their colonies. Rothenbuhler's model proposed that one locus controls the uncapping of brood cells containing dead pupae, while a second controls the removal of the cell contents. We show here, through molecular techniques and quantitative trait loci (QTL) linkage mapping, that the genetic basis of hygienic behavior is more complex, and that many genes are likely to contribute to the behavior. In our cross, we detected seven suggestive QTLs associated with hygienic behavior. Each detected QTL controlled only 9-15% of the observed phenotypic variance in the character.