Creative New

A LEADER IN THE HIVE: THE QUEEN BEE.Via us2.harunyahya

A bee’s future as queen or worker may rest with parasitic fly.Via eurekalert

Genomic dissection of behavioral maturation in the honey bee.Via pubmedcentral.nih.gov

Strange things are happening in the lowland tropical forests of Panama and Costa Rica. A tiny parasitic fly is affecting the social behavior of a nocturnal bee, helping to determine which individuals become queens and which become workers.

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The finding by researchers from the University of Washington and the Smithsonian Tropical Research Institute is the first documented example of a parasite having a positive affect on the social behavior of its host. This is accomplished by cleptoparasitism – in this case fly larvae stealing food from the developing immature bees. The researchers found that smaller bees that emerge in a nest are dominated by their mothers. These small bees are more likely to stay and act as helping workers, while larger bees tend to depart and start new nests as egg-laying queens. Bees that emerge from cells, or brood chambers, that also house flies are smaller than their nest mates from fly-free cells. The flies may encourage worker behavior in some bees.

“We often think of parasitism in terms of it affecting an animal’s fitness, its survival or its ability to reproduce,” said Sean O’Donnell, a UW associate professor of psychology and co-author of the paper appearing in the current issue of the Journal of Insect Behavior. “Here the parasite is not living inside another animal, but is still stealing resources from the host.

“We think these fly parasites are not affecting the lifespan of the bees, and the bees’ mothers benefit by having a helper, or worker, stay around to protect the nest, increasing survivability.”

O’Donnell and his colleagues studied two closely related tropical social bees, Megalopta genalis and Megalopta ecuadoria, and a family of very small parasitic flies calledChloropidae.

The bees are important pollinators of night-blooming plants and the female bees can nest alone or live in small colonies. A colony is typically made up of two to four individuals – a queen and her offspring.

Behavioral observations showed that non-reproductive foragers and guards are significantly smaller than the queen bee in a nest, although the relative size of individual bees varied from nest to nest. Here’s where the flies apparently fit in and are affecting the bees’ behavior. The bees nest in hollowed twigs and sticks hanging in the tropical understory and the flies flick their eggs into the entrance to the bee nests. Some of these eggs randomly fall into cells, or chambers, prepared by the bees, each to hold a larva and pollen that the larva eats. The cells are then sealed, so if a cell does contain fly eggs the young flies are competing with the bee larva for a limited amount of food.

“There is a natural size variation in bees and this is based in part on the amount of food available in the cell,” said O’Donnell. “A fly or flies in a cell reducing the amount of food could be a potentially important factor. It seems that the more flies in a cell the smaller the bee is. The key here is relative body size compared to nest mates. The larger individuals become queens because they are not dominated.”

The researchers were able to culture the bees and flies from individual cells and counted as many as 15 of the tiny flies in a single cell. Some cells did not contain flies.

“This study is a counterintuitive take on parasitic infection. It encourages us to look for complicated ecological relationships between different species. Parasitism may encourage sociality in some situations. Here it is promoting social behavior,” O’Donnell said.

DISCUSSION

Our results demonstrate how a genomic approach can be combined with organismal biology, which, in this case, refers to knowledge about ontogenetic, genetic, physiological, and social components of bee behavior, to help gain insights into the molecular basis of social behavior. This successful dissection of brain gene expression indicates that, for social behavior, gene expression in the brain can provide a robust indicator of the interaction between hereditary and environmental information (23).

Our results, combined with those in refs. 1 and 2, reveal a robust molecular signature for division of labor in honey bee colonies, providing further evidence for a strong connection between brain gene expression and plasticity in naturally occurring behavior (12). Seeley (24) described four behaviorally distinct “temporal castes” in honey bee colonies that were associated with age, task, and task location. Our PCA revealed trends in brain gene expression that were related to these groups of bees. The first group of newly eclosed bees likely corresponds to Seeley’s “cell cleaners” (the first temporal caste, which persists for ≈1 day) and represented the most different and discrete group in PCA (cluster a in Fig. 1B). Although our four hive-bee age groups (days 4, 8, 12, and 17) overlap in age with two of Seeley’s temporal castes, their collection from the brood area at the center of the hive likely places all four age groups (clusters b and c) in Seeley’s “hive center” rather than the subsequent “hive periphery” caste. Seeley’s hive periphery caste was not represented in the current study, but results from another study (13) showed that this group (represented by comb builders, guards, and undertakers) also was distinct in brain gene expression profiles from both nurses (hive-center bees) and foragers. The fourth temporal caste described by Seeley consisted of foragers, which did form a distinct group (cluster d) in the present study. Thus, four worker groups derived from behavioral observation are distinguished by distinct gene expression profiles in the brain.

How Does the Queen Regulate the Gender of Other Bees?

One of the most extraordinary attributes of the queen bee is her ability to regulate the genders of the bees in the hive. The queen regulates gender by opening and closing the mouth of the sac in which sperm are preserved. This sac is connected to the egg laying tube by a thin channel. When the queen wishes to lay a female egg she contracts her muscles, drawing a few sperm from the small sac connected to the egg passage channel, and these fertilise the egg there. As a result of this function given to the queen, female bees hatch from fertilized eggs and males from non-fertilised ones. (4) Despite the queen bee’s regulation of the eggs, it is actually the workers who determine the egg’s gender. Because the egg-laying performed by the queen is carried out in accordance with the cell type prepared by the workers. If the cell the queen approaches is a 5.2 mm standard cell, she will lay a female egg, whereas if it is 1 mm larger, she will lay a male egg in it. (5)