The Honeybee Society

In contrast to the classic models of biological aging research, honeybees represent a species in an advanced state of social evolution. They live their entire lives as part of a complex society, the colony, and cannot survive or reproduce as solitary individuals. The honeybee society rivals traditional human societies in many societal parameters, such as group size, cohesiveness, information exchange, integration, and differentiation of roles (Wilson, 1980), including reproductive division of labor. Honeybees are characterized by a strong colony-level selection component, which has led to functional differentiation of colony members into separate castes and to the concept of regarding the colony as a superorganism (Moritz and Fuchs, 1998): workers fulfill the various roles of the soma (food acquisition, processing, and distribution, home-ostasis, and protection), while the mature queen represents the unique germ line and stem cell (meristem), and males and young queens can be regarded as the gametes.

Typically, a honeybee colony contains one reproductive queen and tens of thousands of female workers that are functionally sterile in the presence of a reproductive queen (de Groot and Voogd, 1954). During the reproductive season, several thousand males (drones) are also found in the nest. Additionally, all stages of the developing juveniles (brood, i.e., eggs, larvae and pupae) and extensive food resources (honey and pollen) are found in the colony. The brood, honey and pollen are stored in the main nest structure, the wax combs. These combs are typically arranged in sheets. The center of the nest is filled with brood, surrounded by a sphere of pollen storage, and the outer areas of the nest are used to store honey (Winston, 1987). All demographic variables have a strong seasonal component, at least in the temperate regions where the majority of studies have been conducted (Winston, 1987). Workers are produced throughout most of the year except for the first part of winter. However, the peak in the production of new workers precedes the production of drones and new queens in the early summer when resources are abundant.

In contrast to individual honeybees, colonies are perennial and potentially immortal through the continuous replacement of their members. The queen, as the only reproducing individual, can live several years (see below), but is regularly replaced by her own daughters (reviewed by Page and Peng, 2001). As part of the regular reproductive cycle, replacement queens are raised and the old queen leaves the nest in a swarm with the majority (50-90%) of the workers present to establish a new colony. One of the new queens takes over the remaining colony, killing all other young queens and engaging in mating flights (Severson, 1984). In contrast, the male reproductive role of honeybee colonies is exerted throughout the mating season by the continuous production of drones. These seek out matings from unrelated virgin queens during mating flights (Winston, 1987). After having been successfully mated, the young queen assumes the reproductive role in the colony, using her stored sperm (over five million) for several years of reproduction, producing up to 2000 eggs per day (Winston, 1987). During this time, the queen does not fulfill any other colony tasks and is attended by a retinue of young workers that clean and feed her.

Honeybees are haplo-diploid (drones are haploid), and their sex is determined by a single gene (Beye et al., 2003). Female caste determination is nutritional: more abundant and higher quality food causes the female larva to develop into a queen, whereas less and lower quality food leads to worker development. It has been shown in cross-fostering experiments that the developmental trajectories start diverging in the bipotent third larval stage. Queens will continue to be fed royal jelly, a highly nutritional food that triggers a juvenile hormone (JH) peak that shifts global gene expression patterns compared to workers (Evans and Wheeler, 1999) and ultimately accelerates their development rate. Worker-destined larvae are reared on an inferior diet which causes them to emerge as adults with half of the body weight of queens (reviewed by Page and Peng, 2001).

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Blood Pressure Health

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