|dc.description.abstract||Escape, learned avoidance, and defensive behavior underlie adaptive response to aversive stimuli. I examined genetic, physiological, and evolutionary correlates of this response in the honey bee (Apis mellifera sp.). Many adaptations have been described as strategies aimed to cope with the interplay between sociality and ecology. Because the primary model systems for neurophysiological, behavioral and genetic work are solitary or subsocial (e.g. fruit fly, rats, mice), sociality may have a greater effect on these processes than currently thought. It is hypothesized that the tradeoffs and interactions between socially and ecologically driven demands enact on limited resources: time, attention, neural substrate at the level of the individual. To test this central hypothesis I compared behavioral response across sterile female workers and solitary-like male drones. The social and ecological tradeoffs hypothesis predict that behavior of the social female workers would be more impacted by the demands of social interactions than those of the less social males in response to aversive stimuli. Below I describe studies that demonstrate a nuanced understanding of social and ecological influences on response to aversive stimuli in honey bee castes.
In this body of work I first examine correlates between individual sensitivity to a negative stimulus (mild shock) and colony level aggression. My experiments identified and described a novel drone behavior, abdomen flexion, which is similar to the sting attempt produced by workers. I used this variable along with measures of locomotion to assess the relationship between drone, worker and colony response. Results from this study validated the genetic hypothesis and showed that indeed worker and drone response both significantly correlated with colony aggressiveness. Yet I found that workers delay the sting response until aversive stimulus (i.e. electric shock) threshold level, whereas males respond in proportion to electric shock level, and not in a threshold fashion.
My second study focused on assessing how social signals of alarm affect individual learning response across highly social sterile female worker and less social male drone honey bees. Results showed that indeed odor presentation affected learning. Response to alarm pheromone was surprising, as avoidance learning improved with presentation and the effect was dose dependent. This pattern was maintained in drone learning performance suggesting that though social signals do modulate individual response, this effect is not dependent on social roles/participation.
Lastly I focused on worker honey bees to assess signals of genetic expression following aversive training. Results showed that when present, signals of expression were localized to the mushroom body of worker honey bees. That changes in CaMKII are localized to the mushroom body is supported by past neurophysiological research. The novel gene, fen-1, also showed a mushroom-body-localized increase in expression suggesting a possible link between long term memory (LTM) processes and DNA recombination/repair components. Contrastingly gene expression of CREB remained constant across time points and brain regions. The three chapters detailed in this thesis outlines an analysis of honey bee perception, response, and integration of aversive stimuli and how these processes are shaped by the social environment. ğ||