The flow of jelly within a honeybee colony

Summary The flow of jelly from 100 nurse bees to the members of two normal-sized colonies was measured during one night. To follow the flow, nurses were injected with ¹⁴C-phenylalanine. They incorporated this label into the protein of their hypopharyngeal (brood food) glands and their own body protein. When they were allowed trophallactic contacts during the investigation period a loss of label and a shift away from the abdomen was observed, indicating protein synthesis in the hypopharyngeal glands from previously stored protein. Very young larvae were fed less frequently than older ones. Younger workers received larger amounts of jelly than older ones, but considerable amounts were given to foragers. Drones behaved similarly. Between one-third and one-half of the distributed jelly was given to imagines; 10% and 16% of all workers received radioactive jelly from 100 nurses in the two colonies during one night. Thus, jelly is a very important food for adult honey bees. There was a remarkable exchange of label within the class of nurses themselves that is interpreted as communication within the social system.Abbreviation dpm decays per minute     

The organization of honeybee ocelli: Regional specializations and rhabdom arrangements

We have re-investigated the organization of ocelli in honeybee workers and drones. Ocellar lenses are divided into a dorsal and a ventral part by a cusp-shaped indentation. The retina is also divided, with a ventral retina looking skywards and a dorsal retina looking at the horizon. The focal plane of lenses lies behind the retina in lateral ocelli, but within the dorsal retina in the median ocellus of both workers and drones. Ventral retinula cells are ca. 25 μm long with dense screening pigments. Dorsal retinula cells are ca. 60 μm long with sparse pigmentation mainly restricted to their proximal parts. Pairs of retinula cells form flat, non-twisting rhabdom sheets with elongated, straight, rectangular cross-sections, on average 8.7 μm long and 1 μm wide. Honeybee ocellar rhabdoms have shorter and straighter cross-sections than those recently described in the night-active bee Megalopta genalis. Across the retina, rhabdoms form a fan-shaped pattern of orientations. In each ocellus, ventral and dorsal retinula cell axons project into two separate neuropils, converging on few large neurons in the dorsal, and on many small neurons in the ventral neuropil. The divided nature of the ocelli, together with the particular construction and arrangement of rhabdoms, suggest that ocelli are not only involved in attitude control, but might also provide skylight polarization compass information.     

Determining colony densities in wild honeybee populations (<Emphasis Type="Italic">Apis mellifera</Emphasis>) with linked microsatellite DNA markers

Estimating the population size of social bee colonies in the wild is often difficult because nests are highly cryptic. Because of the honeybee (Apis mellifera) mating behaviour, which is characterized by multiple mating of queens at drone congregation areas (DCA), it is possible to use genotypes of drones caught at these areas to infer the number of colonies in a given region. However, DCAs are difficult to locate and we assess the effectiveness of an alternative sampling technique to determine colony density based on inferring male genotypes from queen offspring. We compare these methods in the same population of wild honeybees, Apis mellifera scutellata. A set of linked microsatellite loci is used to decrease the frequency of recombination among marker loci and therefore increase the precision of the estimates. Estimates of population size obtained through sampling of queen offspring is significantly larger than that obtained by sampling drones at DCAs. This difference may be due to the more extensive flying range of queens compared with drones on mating flights. We estimate that the population size sampled through queen offspring is about double that sampled through drones.     

Nosema ceranae in drone honey bees (Apis mellifera)

Nosema ceranae is a microsporidian intracellular parasite of honey bees, Apis mellifera. Previously Nosema apis was thought to be the only cause of nosemosis, but it has recently been proposed that N. ceranae is displacing N. apis. The rapid spread of N. ceranae could be due to additional transmission mechanisms, as well as higher infectivity. We analyzed drones for N. ceranae infections using duplex qPCR with species specific primers and probes. We found that both immature and mature drones are infected with N. ceranae at low levels. This is the first report detecting N. ceranae in immature bees. Our data suggest that because drones are known to drift from their parent hives to other hives, they could provide a means for disease spread within and between apiaries.     

The size of wild honeybee populations (<Emphasis Type="Italic">Apis mellifera</Emphasis>) and its implications for the conservation of honeybees

The density of wild honeybee colonies (Apis mellifera) in the African dry highland savannahs was estimated in three Nature Reserves in Gauteng, South Africa (Ezemvelo, Leeuwfontein, Suikerbosrand) based on the genotypes of drones which were caught at drone congregation areas. Densities were estimated to range between 12.4 and 17.6 colonies per square kilometer. In addition colony densities were estimated in two German National parks (Müritz and Hochharz) and a commercial mating apiary. The density of colonies was significantly lower at the German sampling sites with estimates of 2.4–3.2 colonies per square kilometer, which closely matches the nation-wide density of colonies kept by beekeepers. This shows that the densities of colonies observed in wild populations under the harsh conditions of the African dry savannahs exceeds that of Germany by far, in spite of intensive beekeeping. The intensity of apiculture in Europe is therefore unlikely to compensate for the loss of habitats suitable for wild honeybees due to agriculture, forestry and other cultivation of land.     

Amino acids and osmolarity in honeybee drone haemolymph

Summary In the haemolymph of honeybee drones, concentrations of free amino acids were higher than in worker haemolymph, with different relative proportions of individual amino acids. The overall concentration of free amino acids reached its highest level at the 5th day after adult drone emergence, and after the 9^th day only minor changes in the concentration and distribution of free amino acids were observed. This coincides with the age when drones reach sexual maturity and change their feeding behaviour. Levels of essential free amino acids were high during the first 3 days of life and thereafter decreased. Osmolarity was lowest at emergence (334 ± 41 mOsm), increased until the age of 3 days (423 ± 32mOsm) and then stayed generally constant until the 16^th day of life. Only 25-day-old drones had significantly higher osmolarity (532 ± 38 mOsm). The overall change in osmolarity during a drone's lifetime was about 40%.     

Cloning and expression pattern of odorant receptor 11 in Asian honeybee drones,Apis cerana (Hymenoptera,Apidae)

Odorant receptors play a crucial role in the special recognition of scent molecules in the honeybee olfaction system. The odorant receptor 11 (AmOR11) in western honeybee drones (Apis mellifera) has been demonstrated to specifically bind to 9-oxo-2-decenoic acid (9-ODA) of queens. However, little is known regarding the functions of OR11 Asian honeybee drones (Apis cerana) in the context of their mating activities. In this study, the odorant receptor 11 gene (AcOr11) from A. cerana was cloned, and its expression profiles were examined during two developmental stages (immature and sexually mature) and different physiological statuses (flying and crawling). The cDNA sequence of AcOr11 was highly similar to that of AmOr11, and encoded a membrane-coupled protein of 384 amino acids. The results of qRT-PCR indicated that AcOr11 was expressed at higher levels in drone antennae compared to brains, and the expression was significantly up-regulated in sexually mature drone brains compared to immature brains. Interestingly, AcOr11 expression in brains of mature flying drones was dramatically higher than those of mature crawling drones. To our knowledge, this study demonstrate a link between AcOr11 gene expression in the brain of honeybee drones and behavior associated with sexual maturity and mating flight.     

Thermal impact of migrating birds’ wing color on their flight performance: Possibility of new generation of biologically inspired drones

The thermal impact of the birds’ color on their flight performance are investigated. In most of the large migrating birds, the top of their wings is black. Considering this natural phenomenon in the migrating birds, such as albatross, a thermal analysis of the boundary layer of their wings is performed during the year depending on the solar insulation. It is shown that the temperature difference between the bright and dark colored top wing surface is around 10 °C. The dark color on the top of the wing increases the temperature of the boundary layer over the wing which consequently reduces the skin drag force over the wing. This reduction in the drag force can be considered as one of the effective factors for long endurance of these migrating birds. This research should lead to improved designs of the drones by applying the inspired colors which can help drones increase their endurance.