The dynamic association between ovariole loss and sterility in adult honeybee workers.

In the social insects, ovary state (the presence or absence of mature oocytes) and ovary size (the number of ovarioles) are often used as proxies for the reproductive capacity of an individual worker. Ovary size is assumed to be fixed post-eclosion whereas ovary state is demonstrably plastic post-eclosion. Here, we show that in fact ovary size declines as honeybee workers age.

Anarchy Is a Molecular Signature of Worker Sterility in the Honey Bee.

Worker sterility is a defining characteristic of eusociality. The existence of the sterile worker caste remains a fundamental question for evolutionary biology as it requires the existence of genes that reduce personal reproduction. Currently, little is known about the proximate mechanisms underpinning worker sterility.

RNA-sequencing elucidates the regulation of behavioural transitions associated with the mating process in honey bee queens.

Background: Mating is a complex process, which is frequently associated with behavioural and physiological changes. However, understanding of the genetic underpinnings of these changes is limited. Honey bees are both a model system in behavioural genomics, and the dominant managed pollinator of human crops; consequently understanding the mating process has both pure and applied value.

Regulation of oogenesis in honey bee workers via programed cell death.

Reproductive division of labour characterises eusociality. Currently little is known about the mechanisms that underlie the 'sterility' of the worker caste, but queen pheromone plays a major role in regulating the reproductive state. Here we investigate oogenesis in the young adult honey bee worker ovary in the presence of queen pheromone and in its absence.

Steroid hormone (20-hydroxyecdysone) modulates the acquisition of aversive olfactory memories in pollen forager honeybees.

Here, we examine effects of the steroid hormone, 20-hydroxyecdysone (20-E), on associative olfactory learning in the honeybee, Apis mellifera. 20-E impaired the bees' ability to associate odors with punishment during aversive conditioning, but did not interfere with their ability to associate odors with a food reward (appetitive learning). The steroid had a significant impact also on the expression of amine-receptor genes in centers of the brain involved in the formation and recall of associative olfactory memories (mushroom bodies).

Effects of natural mating and CO2 narcosis on biogenic amine receptor gene expression in the ovaries and brain of queen honey bees, Apis mellifera.

A queen honey bee mates at ∼6 days of age, storing the sperm in her spermatheca for life. Mating is associated with profound changes in the behaviour and physiology of the queen but the mechanisms underlying these changes are poorly understood. What is known is that the presence of semen in the oviducts and spermatheca is insufficient to initiate laying, and that copulation or CO(2) narcosis is necessary for ovary activation.

Biogenic amine receptor gene expression in the ovarian tissue of the honey bee Apis mellifera.

In the honey bee Apis mellifera loss of the queen from a colony induces increased levels of the biogenic amine dopamine in the brain of workers, and this elevation is correlated with ovary activation. In the present study we use real-time quantitative PCR to investigate expression of five biogenic amine receptor genes. We show that biogenic amine receptors are expressed in ovarian tissue, and that their expression is strongly influenced by the presence or absence of a queen in the colony.

Peripheral modulation of worker bee responses to queen mandibular pheromone.

It is generally accepted that young worker bees (Apis mellifera L.) are highly attracted to queen mandibular pheromone (QMP). Our results challenge this widely held view.

Olfactory conditioning of the sting extension reflex in honeybees: Memory dependence on trial number, interstimulus interval, intertrial interval, and protein synthesis.

Harnessed bees learn to associate an odorant with an electric shock so that afterward the odorant alone elicits the sting extension response (SER). We studied the dependency of retention on interstimulus interval (ISI), intertrial interval (ITI), and number of conditioning trials in the framework of olfactory SER conditioning. Forward ISIs (conditioned stimulus [CS] before unconditioned stimulus [US]) supported higher retention than a backward one (US before CS) with an optimum around 3 sec.

Queen pheromone blocks aversive learning in young worker bees.

Queen mandibular pheromone (QMP) has profound effects on dopamine signaling in the brain of young worker honey bees. As dopamine in insects has been strongly implicated in aversive learning, we examined QMP's impact on associative olfactory learning in bees. We found that QMP blocks aversive learning in young workers, but leaves appetitive learning intact.

Aversive learning in honeybees revealed by the olfactory conditioning of the sting extension reflex.

Invertebrates have contributed greatly to our understanding of associative learning because they allow learning protocols to be combined with experimental access to the nervous system. The honeybee Apis mellifera constitutes a standard model for the study of appetitive learning and memory since it was shown, almost a century ago, that bees learn to associate different sensory cues with a reward of sugar solution. However, up to now, no study has explored aversive learning in bees in such a way that simultaneous access to its neural bases is granted.

Queen pheromone modulates brain dopamine function in worker honey bees.

Honey bee queens produce a sophisticated array of chemical signals (pheromones) that influence both the behavior and physiology of their nest mates. Most striking are the effects of queen mandibular pheromone (QMP), a chemical blend that induces young workers to feed and groom the queen and primes bees to perform colony-related tasks. But how does this pheromone operate at the cellular level? This study reveals that QMP has profound effects on dopamine pathways in the brain, pathways that play a central role in behavioral regulation and motor control.