Male bumblebees (Bombus terrestris) are more active and behaviourally flexible than workers.

SUMMARYInvestigations of queen, worker and male bumble bees (Bombus terrestris) showed that all individuals became infected with Nosema bombi. Infections were found in Malpighian tubules, thorax muscles, fat body tissue and nerve tissue, including the brain. Ultrastructural studies revealed thin walled emptied spores in host cell cytoplasm interpreted as autoinfective spores, besides normal spores (environmental spores) intended for parasite transmission between hosts. The nucleotide sequence of the gene coding for the small subunit rRNA (SSU-rRNA) from Microsporidia isolated from B. terrestris, B. lucorum, and B. hortorum were identical, providing evidence that N. bombi infects multiple hosts. The sequence presented here (GenBank Accession no AY008373) is different from an earlier submission to GenBank (Accession no U26158) of a partial sequence of the same gene based on material collected from B. terrestris. It still remains to be investigated if there is species diversity among Microsporidia found in bumble bees.

Bumblebee (Bombus terrestris L.) is a bee race that take part in pollination. It is though Bumblebee (Bombus terrestris L.) is only used in pollination. But, it is not only take part in pollination, it provide to produce different products. Nest cover wax material is a kind of bee product that produced by Bumblebee (Bombus terrestris L.). Although it is considered to be waste, nest cover wax material is an important hive product with its antioxidant and antimicrobial activities. In this study, Bumblebee nest cover wax material was produced under laboratory conditions in a controlled manner. Biochemical characterization of nest cover wax material obtained from five different colonies was performed and antimicrobial activities were determined. Accordingly, it was determined that the total phenolic content of the samples ranged between 3.778±0.165 and 9.504±0.353 mg GAE/g. In addition, it was observed that the samples were rich in p-coumaric acid, luteolin, quercetin, t-sinnamic acid, chrysin and pinocembrin components. It was determined that nest cover wax material, which also showed antimicrobial activity, had nearly equivalent activity to beehive products such as honey, pollen and bee bread. The data obtained show that nest cover wax material will be an alternative product for apitherapy applications.

Heterozygosity at loci affecting resistance against parasites can benefit host fitness. We predict that, in haplodiploid species, haploid males will suffer decreased parasite resistance relative to diploid females. We suggest that elevated susceptibility in haploid males has shaped the evolution of social behaviour in haplodiploid species. Male susceptibility will select for behavioural adaptations that limit males' exposure to pathogens and that limit male transmission of pathogens within and between colonies. The relatedness-asymmetry hypothesis that has been advanced to explain female-only workers does not make these predictions. We review the relevant evidence for genetic effects on parasite resistance in insects and summarize empirical evidence that relates to the haploid-susceptibility hypothesis.

Elevated developmental temperature affects gene expression and oxidative stress in bumblebee (Bombus terrestris) workers

The natural world is constantly changing, especially with climate change looming over different aspects of it. Humans are therefore affected, but creatures much smaller than humans are taking the brunt of the impact of climate change. Some creatures, such as the insects that pollinate food for humans, are facing critical declines. While climate change is directly impacting many different parts of an insect's life, a research group from the Republic of Korea and New Zealand focused on how climate heating impacts how buff-tailed bumblebees (Bombus terrestris), a very important pollinating insect, choose their mates, which is critical for the future of bumblebee colonies. Min Su Park, Ji Hyun Woo, Hyung Joo Yoon, Bo Yeon Kim, Kwang Sik Lee and Byung Rae Jin (Dong-A University, Republic of Korea), Steven A. Trewick (Massey University Manawatu, New Zealand) and Kyeong Yong Lee (National Academy of Agricultural Science, Republic of Korea) collaborated to examine how rising temperatures affected how males compete to attract a mate and how females choose the males they want to mate with.The researchers collected male bees and queen bees from several colonies, measured their body mass and categorized each male as small, medium or large. They then tested the insects’ preferences for a mate by placing equal numbers of large and small male bees with medium-sized queens inside a mating box for 2 h, keeping track of how often the bees mated, when and for how long. In another set of mate-choice tests, Park and colleagues placed equal numbers of large and small queens with medium-sized males in a mating box for the same length of time. Having conducted the tests at a low temperature (23°C), they then repeated them at the higher temperature of 32°C to see if it would affect anything. Additionally, they checked the males’ sperm count at the end of each mating session.Once the researchers had analyzed all of their measurements, they found some things that aligned with the measurements that other scientists had made previously, where body size does indeed matter for male and female buff-tailed bumblebees when looking for a mate. The team found that the largest male bumble bees (with the largest body mass) mated more than smaller male bumble bees. And when the researchers looked at how long each bee couple mated for, it took longer for the smaller male bees to complete mating and the larger males’ sperm counts were higher after mating had finished. In addition, when the researchers looked at which females the males preferred to mate with, they found that large queens mated much more with large males.Interestingly, body size mattered even more in the heat. At cooler temperatures, queens mated with both large and small males equally. But at 32°C, large males mated more often and passed on more sperm to the queens, because they had higher sperm counts. Queens also preferred larger mates when it was warmer. Plus, heavier queens tended to survive winter better, so size affected not just mating but also survival. Both temperature and body mass play a key role in the act of mating, as it can really determine the fate of future bumblebees.Both large males and large queens have characteristics that would benefit them in the long run. For example, large males have a higher sperm count, which is good because it gives the males a better chance of fertilizing the queen’s eggs, resulting also in success for the female with a lot of new baby bees and a successful colony. And large queens are more likely to survive through the winter, which is the first step for queens to produce a successful colony the following spring.

Event Abstract Back to Event Testing colour discrimination models with free-flying bumblebees (Bombus terrestris L.): the unexpected effect of inspection time Francismeire J. Telles1* and Miguel A. Rodríguez-Gironés1 1 Estación Experimental de Zonas Áridas -EEZA, Departament of Functional and Evolutionary Ecology , Spain Several models have been proposed to explain how bees see and discriminate colours. To investigate the accuracy of two contending models, the colour hexagon and the colour opponent coding model (COC), we trained 64 bumblebees to discriminate between four colour pairs (16 bees per pair), having the same hexagon units (0.05) but differing in their COC distances (0.55-1.5 units). While the proportion of correct choices increased with COC distance, the effect was mediated by an increase in the time that bumblebees spent inspecting colours before choosing one, and the effect of COC distance on performance disappeared after statistically correcting for inspection time. Neither of the models could fully account for the data: the colour hexagon model cannot explain the relationship between COC distance and inspection time, and the COC model predicted that, after correcting for inspection time, performance should increase with COC distance. Figure 1 Acknowledgements Spanish National Research Council – CSIC and Estación Experimental de Zonas Áridas – EEZA. This work was supported by CGL2010-16795 References Backhaus, W. (1991). Color Opponent Coding in the Visual System of the Honeybee. Vision Res., 31(7), 1381–1397. Chittka, L. (1992). The colour hexagon: a chromaticity diagram based on photoreceptor excitations as a generalized representation of colour opponency. Journal of Comparative Physiology A, 170(5), 533–543. doi:10.1007/BF00199331 Keywords: Bumblebees, vision models, Colour discrimination, search time, Colour Hexagon Model, Colour Opponent Coding Model Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Poster presentation preferred Topic: Colour and polarisation vision Citation: Telles FJ and Rodríguez-Gironés MA (2019). Testing colour discrimination models with free-flying bumblebees (Bombus terrestris L.): the unexpected effect of inspection time. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00108 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Apr 2013; Published Online: 09 Dec 2019. * Correspondence: Miss. Francismeire J Telles, Estación Experimental de Zonas Áridas -EEZA, Departament of Functional and Evolutionary Ecology, Almería, Almería, 04120, Spain, meirecuesta@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Francismeire J Telles Miguel A Rodríguez-Gironés Google Francismeire J Telles Miguel A Rodríguez-Gironés Google Scholar Francismeire J Telles Miguel A Rodríguez-Gironés PubMed Francismeire J Telles Miguel A Rodríguez-Gironés Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Simple SummaryA vast array of microorganisms colonize invertebrates and vertebrates. Most of these microbes reside in the digestive tract, where they constitute the intestinal (gut) microbiome. Some microbes are commensal, coexisting with their host without causing harm, while others can be mutualistic or pathogenic. Mutualistic microorganisms perform many health-related functions such as promoting digestion and acquisition of nutrients; hormone regulation; maintenance and control of the immune system; regulation of homeostasis and stress physiology of the body; insecticide resistance; production of certain vitamins; and providing protection against pathogenic microorganisms, parasites, and diseases. Bee-specific bacterial genera such as Lactobacillus, Snodgrassella, and Gilliamella dominate the gut communities of many bumblebees. This study confirmed Lactobacillus, Snodgrassella, and Gilliamella as dominant gut bacteria of the buff-tailed bumblebee Bombus terrestris in the agricultural landscape. However, we show that the guts of B. terrestris from natural forest habitats can be dominated by fructose-associated Fructobacillus spp. Our findings may have important implications for understanding the ecological role of bumblebees and the reasons for the decline of key pollinators.Bumblebees are key pollinators in agricultural landscapes. However, little is known about how gut microbial communities respond to anthropogenic changes. We used commercially produced colonies of buff-tailed bumblebees (Bombus terrestris) placed in three habitats. Whole guts (midgut, hindgut, and rectum) of B. terrestris specimens were dissected from the body and analyzed using 16S phylogenetic community analysis. We observed significantly different bacterial community composition between the agricultural landscapes (apple orchards and oilseed rape (Brassica napus) fields) and forest meadows, whereas differences in gut communities between the orchards and oilseed rape fields were nonsignificant. Bee-specific bacterial genera such as Lactobacillus, Snodgrassella, and Gilliamella dominated gut communities of B. terrestris specimens. In contrast, the guts of B. terrestris from forest meadows were dominated by fructose-associated Fructobacillus spp. Bacterial communities of workers were the most diverse. At the same time, those of males and young queens were less diverse, possibly reflecting greater exposure to the colony’s inner environment compared to the environment outside the colony, as well as bumblebee age. Our results suggest that habitat quality, exposure to environmental microbes, nectar quality and accessibility, and land use significantly affect gut bacterial composition in B. terrestris.

Among the large number of exocrine glands described in bees, the tarsal glands were thought to be the source of footprint scent marks. However, recent studies showed that the compounds used for marking by stingless bees are secreted by leg tendon instead of tarsal glands. Here, we report on the structure of leg tendon glands in males of Bombus terrestris, together with a description of the chemical composition of their secretions and respective changes of both during the males' lives. The ultrastructure of leg tendon glands shows that the secretory cells are located in three independent regions, separated from each other by unmodified epidermal cells: in the femur, tibia, and basitarsus. Due to the common site of secretion release, the organ is considered a single secretory gland. The secretion of the leg tendon glands of B. terrestris males differs in its composition from those of workers and queens, in particular by (1) having larger proportions of compounds with longer chain lengths, which we identified as wax esters; and (2) by the lack of certain hydrocarbons (especially long chain dienes). Other differences consist in the distribution of double bond positions in the unsaturated hydrocarbons that are predominantly located at position 9 in males but distributed at seven to nine different positions in the female castes. Double bond positions may change chemical and physical properties of a molecule, which can be recognized by the insects and, thus, may serve to convey specific information. The function of male-specific compounds identified from their tendon glands remains elusive, but several possibilities are discussed.

Reproductive competence in male bumblebees ( Bombus terrestris ) is contingent upon the precise orchestration of spermatogenesis, governed by the temporal regulation of genes involved in mitochondrial metabolism and flagellar assembly. Although bumblebees serve as ecologically and agriculturally indispensable pollinators, the molecular underpinnings of testicular development in drones remain poorly elucidated. We conducted stage‐resolved transcriptomic profiling of B. terrestris drone testes at three critical post‐eclosion intervals—Days 1, 5, and 9—to capture gene expression dynamics associated with sperm development. A total of 620 differentially expressed genes (DEGs) were identified and grouped into four discrete temporal expression clusters. Gene Ontology (GO) and KEGG pathway enrichment analyses revealed substantial transcriptional reprogramming associated with mitochondrial bioenergetics, cytoskeletal remodeling, and flagellar motility. This transcriptomic analysis of B. terrestris drone testes identified a precise, stage‐specific transcriptional program involving early proliferation and detoxification (Day 1), mitochondrial metabolic priming (Day 5), and robust activation of ATP synthesis and flagellar assembly (Day 9). Despite a slight temporal offset between molecular (Day 9) and physiological maturity (peak mating at Day 7), identified key genes—including inositol 2‐dehydrogenase, flagellar attachment zone protein, flagellar hook‐length control protein, and axonemal dynein intermediate chain—serve as candidate molecular biomarkers for reproductive fitness. These findings provide foundational genomic resources for advancing pollinator breeding and conservation strategies.

No effect of juvenile hormone on task performance in a bumblebee (Bombus terrestris) supports an evolutionary link between endocrine signaling and social complexity

Foraging activity in social insects should be regulated by colony nutritional status and food availability, such that both the emission of, and response to, recruitment signals depend on current conditions. Using fully automatic radio-frequency identification (RFID) technology to follow the foraging activity of tagged bumblebees (Bombus terrestris) during 16,000 foraging bouts, we tested whether the cue provided by stored food (the number of full honeypots) could modulate the response of workers to the recruitment pheromone signal. Artificial foraging phero- mones were applied to colonies with varied levels of food reserves. The response to recruitment pheromones was stronger in colonies with low food, resulting in more workers becoming active and more foraging bouts being performed. In addition to previous reports showing that in colonies with low food successful foragers perform more excited runs during which they release recruitment phero- mone and inactive workers are more prone to leave the nest following nectar influx, our results indicate that evolution has shaped a third pathway that modulates bumblebee foraging activity, thus preventing needless energy expendi- ture and exposure to risk when food stores are already high. This new feedback loop is intriguing since it involves context-dependent response to a signal. It highlights the integration of information from both forager-released pheromones (signal) and nutritional status (cue) that occurs within individual workers before making the decision to start foraging. Our results support the emerging view that responses to pheromones may be less hardwired than commonly acknowledged.

Innate sensory biases could play an important role in helping naïve animals to find food. As inexperienced bees are known to have strong innate colour biases we investigated whether bumblebee (Bombus terrestris) colonies with stronger biases for the most rewarding flower colour (violet) foraged more successfully in their local flora. To test the adaptive significance of variation in innate colour bias, we compared the performance of colour-naïve bees, from nine bumblebee colonies raised from local wild-caught queens, in a laboratory colour bias paradigm using violet (bee UV-blue) and blue (bee blue) artificial flowers. The foraging performance of the same colonies was assessed under field conditions. Colonies with a stronger innate bias for violet over blue flowers in the laboratory harvested more nectar per unit time under field conditions. In fact, the colony with the strongest bias for violet (over blue) brought in 41% more nectar than the colony with the least strong bias. As violet flowers in the local area produce more nectar than blue flowers (the next most rewarding flower colour), these data are consistent with the hypothesis that local variation in flower traits could drive selection for innate colour biases.

1. Life‐history traits such as immunity are often characterised by the presence of large phenotypic variation, but it often remains unclear how and why this variation is maintained by selection. 2. Here an annual social insect, the bumblebee Bombus terrestris , was used to study variation in encapsulation response of males and workers. Bumblebees are a suitable system to study offspring immunity because they are host to a broad variety of different parasites. Bumblebee males, in particular, have a long lifespan compared with other social insect males and their immunity should therefore be an important element for colony reproductive success. 3. Encapsulation response, which was used here as a measurement for the generalised immune defence capacity of an individual, was found to be a highly variable trait. High levels of worker response correlated with low levels of colony parasitism rates. 4. Encapsulation response was found to be (a) lower in males compared with sister workers, and (b) lower in late‐produced cohorts compared with early ones. 5. In colonies with delayed sexual reproduction, males had a lower encapsulation response. Thus, investments into immunity seemed reduced in later male cohorts and those eclosing later in the season, perhaps because males had a shorter expected remaining time to acquire matings. The results presented add further evidence that immune defence is a key variable defining colony fitness in social insects.

Reinventing the plant

The arrival of exotic pollinators to new habitats may introduce new patterns of floral preference and foraging behavior that modify the structure of the resident plant–pollinator community. The aim of this paper is to examine the potential impact of the exotic bumblebee Bombus terrestris on the pollination service provided by the native pollinator assemblage of the herb Mimulus luteus. The study was performed in a high-elevation locality in the Chilean Andes during the summer seasons of 2010, 2011, and 2012. We recorded visitation rate, and the number of pollen grains transported on the body of B. terrestris and native pollinators and the pollen deposition on the stigmas of M. luteus. Pollinator effectiveness (pollen deposited × visitation rate) was compared among species. Results revealed that B. terrestris was an inefficient pollinator, due to the low amount of pollen delivered on stigmas and the low and intermittent visitation rate across years. The parallel inter-annual variation in the visitation rate of B. terrestris and the native bumblebee Bombus dahlbomii suggests that the integration of B. terrestris had no important consequences for the congeneric species. In general, B. terrestris accounted for a low proportion of the pollen transfer in M. luteus, reaching 4.6 % in 2010, absence of effect in 2011, and 0.01 % in 2012. These results suggest that in spite of being a quickly spreading species in Chile, B. terrestris is still in the initial phase of invasion in this area.