How do flies learn and how are their brains influenced by irradiation?
At the moment I am developing an aversion learning assay for the tephritid fruit fly, Bactrocera tryoni. These flies are major agricultural pests in Australia and are being controlled using the Sterile Insect Technique, where flies are irradiated to cause sterility and released outside to mate with wild flies. It is important that irradiatied flies are attractive mates to wild flies. By determining whether we can teach flies to learn to avoid something they are attracted to, we can test the influence of several factors (including irradiation) on fly learning ability. I am also using microCT to examine the effects of irradiation on fly brains.
How does the honey bee colony work and what makes it collapse?
Some of my work investigates how external stressors affect the honey bee colony. To do this, we have investigated how honey bee colonies react to exposure to crops containing neonicotinoid pesticides. This family of pesticide blocks receptors in the honey bee brain, and previous work suggests that bees exposed to these pesticides (at sublethal levels) are mentally impaired. We are examining how neonicotinoids accumulate in the hive (they are present in pollen and nectar), how the bees are affected by them and what effects these pesticides have on the hive as a whole.
A honey bee hive contains a complex society, where everyone has a job. The queen lays eggs, young workers feed and care for brood, and maintain the nest while older workers forage for resources for the colony. In bees that are less social, the queen will physically attack her workers in order to make them work for her. In highly social honey bees, this ‘worker’s contract’ is mediated by pheromones. I wanted to know why workers work for the queen instead of having their own offspring? We found that the queen’s pheromone blend is highly correlated to her mating status, and that when the queen was able to produce lots of brood (workers’ sisters), workers had inactive ovaries and refrained from reproduction. When the queen was potentially less fertile, workers started activating their ovaries, suggesting that when the queen can produce lots of sisters for the workers (and therefore high worker inclusive fitness) it is likely adaptive for workers to work for the queen (Peso, Niño, Grozinger and Barron, Insectes Sociaux, 2012) also see (Peso, Elgar and Barron, Biological Reviews, 2014).
Then I asked what happens in a bee hive when the queen is no longer present? We found that without the queen and her pheromone, individual workers lay eggs, forage, and maintain and defend the nest, losing the specialisation observed in colonies with a queen. This ‘jack of all trades’ honey bee worker state resembles those of their likely ancestors, communal bees, that share living space, but engage in their own reproduction (Naeger, Peso, Even, Barron and Robinson, Current Biology, 2013). This story has another chapter in which we investigate what is going on in the brains of these queenless worker honey bees (Peso, Even, Søvik, Naeger, Robinson and Barron, Journal of Comparative Physiology A, 2016).
As developing brood emits a pheromone in the hive as well, I wanted to know how adding supplementary brood pheromone to colonies in different stages of growth would affect foraging and colony growth (Peso and Barron, Apidologie, 2014). The answer is it’s complicated, but you can read my paper to find out more.
Signalling by waving: how male fiddler crabs attract the ladies
Above left: male Uca mjoebergi fiddler crab. Above right: a female Uca mjoebergi laden with eggs. (Photo credits: Wil Splinter)
The fiddler crab, U. mjoebergi lives in densely-populated patches on the mudflats of Darwin, Australia. In these patches, females wander across the mudflats, looking for mates. Males wave their large, yellow claw madly signalling to try and capture the attention of wandering females. But females are picky, and can reject up to 13 males before choosing a mate (Reaney and Backwell 2007). Females generally like males with big claws and fast waves (Reaney 2009), but when we presented females with robotic crabs of different claw sizes and wave rates, we found that at a distance, the preference disappears (Peso, Telford and Backwell, Animal Behaviour, 2014). Also, we found that females only preferentially choose males with big claws and fast waves when the choices were adjacent to each other, and only when the female was released relatively close to the simulated males (Peso, Telford and Backwell, Animal Behaviour, 2014). Taken together, these results suggest that the claw size and wave rate matters when the female relatively close to the male and when she can compare waving males directly within her field of view.
Signalling nest membership in the carpenter bee, Xylocopa virginica
X. virginica are facultatively eusocal, meaning that a female can establish a nest alone, or share nest space with other females (presumably her sisters). I wanted to know if, somehow, both males and females can distinguish members of their own nest from non-nestmates, turns out they can (Peso and Richards, Animal Behaviour, 2010) despite the fact that nest membership changes frequently (Peso and Richards, Insectes Sociaux, 2011)!