Thermal Impacts of Apicultural Practice and Products on the Honey Bee Colony

Hive design and apicultural processes have not been fundamentally changed since the design and commercialization of the Langstroth moveable frame hive in 1854. Colonies of Apis mellifera Linnaeus (Hymentoptera: Apidae) (the honey bee) maintain a brood nest temperature within the narrow range of 34.5–35.5°C, critical for brood development. Apis mellifera invest considerable energy to maintain hive homeostasis through behavioral modification of the hive environment. Human honey-harvesting processes and removal of the honey-filled comb (a source of thermal mass) have a detrimental impact on hive temperature that requires an increased investment of energy to rectify. This additional energy demand on the bees is a form of stress to the colony and diverts workers away from other essential tasks to that of environmental management. We investigated the thermal energy loss resulting from the removal and extraction of honey, the rate of thermal loss of an Australian standard Langstroth 10 frame hive, and the effect of honey and wax as a thermal mass in unoccupied bee hive. The results demonstrate that considerable energy expenditure would be required to rectify the hive thermal environment after honey harvesting or honeycomb frame addition. Honey provides thermal mass in the beehive, acting as a thermal buffer to external temperature change, which may mediate part of the thermal losses from the simplistic design of the Langstroth hive. Identification of these impacts in current apicultural practice and hive design allows for the improvement in the design of beehives and associated practices. These improvements may reduce stress to the bee colony, increasing colony efficiency for pollination and nectar foraging.

The evolution of queen control over worker reproduction in the social Hymenoptera

A trademark of eusocial insect species is reproductive division of labor, in which workers forego their own reproduction while the queen produces almost all offspring. The presence of the queen is key for maintaining social harmony, but the specific role of the queen in the evolution of eusociality remains unclear. A long-discussed scenario is that a queen either behaviorally or chemically sterilizes her workers. However, the demographic and ecological conditions that enable such manipulation are unknown. Accordingly, we propose a simple model of evolutionary dynamics that is based on haplodiploid genetics. We consider a mutation that acts in a queen, causing her to control the reproductive behavior of her workers. Our mathematical analysis yields precise conditions for the evolutionary emergence and stability of queen-induced worker sterility. These conditions do not depend on the queen's mating frequency. Moreover, we find that queen control is always established if it increases colony reproductive efficiency and can evolve even if it decreases colony efficiency. We further outline the conditions under which queen control is evolutionarily stable against invasion by mutant, reproductive workers.

Individual personalities shape task differentiation in a social spider

Deciphering the mechanisms involved in shaping social structure is key to a deeper understanding of the evolutionary processes leading to sociality. Individual specialization within groups can increase colony efficiency and consequently productivity. Here, we test the hypothesis that within-group variation in individual personalities (i.e. boldness and aggression) can shape task differentiation. The social spider Stegodyphus sarasinorum (Eresidae) showed task differentiation (significant unequal participation) in simulated prey capture events across 10-day behavioural assays in the field, independent of developmental stage (level of maturation), eliminating age polyethism. Participation in prey capture was positively associated with level of boldness but not with aggression. Body size positively correlated with being the first spider to emerge from the colony as a response to prey capture but not with being the first to attack, and dispersal distance from experimental colonies correlated with attacking but not with emerging. This suggests that different behavioural responses to prey capture result from a complex set of individual characteristics. Boldness and aggression correlated positively, but neither was associated with body size, developmental stage or dispersal distance. Hence, we show that personalities shape task differentiation in a social spider independent of age and maturation. Our results suggest that personality measures obtained in solitary, standardized laboratory settings can be reliable predictors of behaviour in a social context in the field. Given the wealth of organisms that show consistent individual behavioural differences, animal personality could play a role in social organization in a diversity of animals.

Juveniles and the elderly defend, the middle-aged escape: division of labour in a social aphid

In colonies of social insects, non-random spatial positioning within the colonies may reflect division of labour and improve colony efficiency. Here, we describe a novel defence system in the colony of a gall-forming social aphid, Quadrartus yoshinomiyai (Nipponaphidini), where young and old defensive aphids move towards the dangerous area typically associated with a higher risk of predation, whereas the middle-aged reproductive individuals move away. Younger nymphs and post-reproductive adults of Q. yoshinomiyai concurrently defend against predators that intrude after their galls open. In natural open galls, both types of defenders were preferentially located around the open area vulnerable to invasion by predators, whereas reproductive individuals remained in the safer areas. In addition, when a hole was artificially made in closed galls, these morphs located themselves in similar spatial positions to the natural open galls within 12 hours. The defensive system led by oldest and youngest individuals may reflect the possibility of future reproduction for these insects, thereby optimizing colony efficiency in a seasonally changing environment, according to the reproductive values of colony members.

Reproductive constraint is a developmental mechanism that maintains social harmony in advanced ant societies

A hallmark of eusociality in ants is the reproductive division of labor between queens and workers. Yet, nothing is known about the molecular mechanisms underlying reproduction in this group. We therefore compared the developmental genetic capacity of queens and workers to reproduce in several eusocially advanced species from the two largest subfamilies of ants, the Myrmicinae and Formicinae. In flies, the asymmetric localization of maternally encoded determinants (mRNAs and proteins) during oogenesis establishes oocyte polarity and subsequently ensures proper embryonic development. Vasa and nanos, two key maternal determinants, are properly localized in the posterior of queen oocytes, but their localization is impaired in those of the workers. This mislocalization leads to severe embryonic defects in worker progeny, and therefore, represents a constraint on worker reproduction that we call ‘reproductive constraint.’ We show that reproductive constraint is phylogenetically widespread, and is at high levels in most species tested. Reproductive constraint can simultaneously reduce or eliminate the workers' ability to produce viable eggs for reproduction, while preserving their ability to produce trophic eggs for nutrition, and thus, may have been the basis for the evolutionary retention of worker ovaries in the majority of ants. We propose that high levels of reproductive constraint has most likely evolved as a consequence of selection at the colony level to reduce or eliminate any potential conflict over worker reproduction, therefore maintaining harmony and colony efficiency in advanced ant societies.

Division of labour and colony efficiency in social insects: effects of interactions between genetic architecture, colony kin structure and rate of perturbations

The efficiency of social insect colonies critically depends on their ability to efficiently allocate workers to the various tasks which need to be performed. While numerous models have investigated the mechanisms allowing an efficient colony response to external changes in the environment and internal perturbations, little attention has been devoted to the genetic architecture underlying task specialization. We used artificial evolution to compare the performances of three simple genetic architectures underlying within-colony variation in response thresholds of workers to five tasks. In the ‘deterministic mapping’ system, the thresholds of individuals for each of the five tasks is strictly genetically determined. In the second genetic architecture (‘probabilistic mapping’), the genes only influence the probability of engaging in one of the tasks. Finally, in the ‘dynamic mapping’ system, the propensity of workers to engage in one of the five tasks depends not only on their own genotype, but also on the behavioural phenotypes of other colony members. We found that the deterministic mapping system performed well only when colonies consisted of unrelated individuals and were not subjected to perturbations in task allocation. The probabilistic mapping system performed well for colonies of related and unrelated individuals when there were no perturbations. Finally, the dynamic mapping system performed well under all conditions and was much more efficient than the two other mapping systems when there were perturbations. Overall, our simulations reveal that the type of mapping between genotype and individual behaviour greatly influences the dynamics of task specialization and colony productivity. Our simulations also reveal complex interactions between the mode of mapping, level of within-colony relatedness and risk of colony perturbations.

Finding One's Mate in a King Penguin Colony: Efficiency of Acoustic Communication

In the king penguin, during the three months of incubation and the brooding stage, members of a pair alternate care duties on land with foraging trips. Contrary to most of the species of birds that nest at a fixed location, the king penguin carries its egg on its feet during incubation. This allows the incubating parents to move in the colony. Brooding or incubating parents moved on average 4.4 meters between egg-laying and the end of the brooding stage. This movement in a group of thousands of other birds reduced the reliability of visual cues for recovering the pair mate during the change-over. We showed that the difficulty in relocating the mate was more important during the brooding stage than during incubating. We confirmed earlier findings that acoustic communication was the main mode of communication during a change-over, and showed that the omnidirectional properties of sound allowed birds to reach more than five hundred other birds with each emitted call. Our experiments proved that the communication system is performed at short or medium range. On average, the birds identified their mate at a distance of 8.8 m. Seventy percent of the birds started the acoustic search of their mate when the distance was shorter or equal to this discrimination range, and so acoustic communication is a particularly efficient strategy in the king penguin. Chez le manchot royal (Aptenodytes patagonicus) le male et la femelle participent tous deux a l'incubation et a l'elevage du poussin. Si en general les oiseaux possedent un nid dont la position fixe aide les deux partenaires a se retrouver lors des releves, le manchot royal est une des rares especes sans nid. En effet, l'adulte incube et protege son oeuf ou son poussin sur ses pattes ce qui lui permet de se deplacer dans la colonie. Nous avons mesure un deplacement moyen de 4.4 metres entre le moment de la ponte et la fin de l'elevage individuel. Ce deplacement parmis des milliers d'autres oiseaux morphologiquement semblables rend tous reperes visuels inutilisables lors des releves entre male et femelle. Pour se reconnaitre individuellement, les manchots utilisent une signature acoustique. Nous avons montre que les proprietes omnidirectionelles du son permettent au manchot qui cherche son partenaire de communiquer potentiellement avec plus de 500 oiseaux pour chaque chant emis. La degradation rapide de la signature lors de la propagation du signal dans la colonie ne permet pas une communication a longue distance: les oiseaux identifient le chant de leur partenaires a une distance moyenne de 8.8 metres. La majorite des manchots royaux (70%) commencent a chanter a une distance inferieure ou egale a la portee du signal ce qui revele une strategie de communication particulierement efficace.

Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.