The Role of Temperature on the Development of Circadian Rhythms in Honey Bee Workers

Abstract

Circadian rhythms in honey bees are involved in various processes that impact colony survival. For example, young nurses take care of the brood constantly throughout the day and lack circadian rhythms, while foragers use the circadian clock to remember and predict food availability in subsequent days. Previous studies suggested that development of circadian rhythms both in the field and the laboratory began around 7-9 days of age. However, not much is understood about the postembryonic development of circadian rhythms in honey bees. In the current study, we examine the effects of socially regulated colony temperature on the ontogeny of circadian rhythms of young workers under controlled laboratory conditions. We hypothesized that temperature plays a key role in the development of circadian rhythmicity in young workers. Our results show that young workers kept at 35{degrees}C develop circadian rhythmicity faster and in greater proportion than bees kept at 25{degrees}C. In addition, we examine if the effect of colony temperature during the first 48 hours after emergence is enough to observe effects on the rate and proportion of development of circadian rhythmicity. We observed that twice as many individuals that were exposed to 35{degrees}C during the first 48 hours develop circadian rhythms compared to individuals kept at 25{degrees}C. In addition, we observed differences in the average endogenous period length consistent with temperature compensation of the circadian rhythms between the 25{degrees}C and 35{degrees}C cohorts. We also observed differences in the degree of period length variation between the 25{degrees}C and 35{degrees}C cohorts, which combined with the proportion of arrhythmic individuals and survival data suggest that development of circadian rhythms is incomplete in individuals exposed to 25{degrees}C adult emergence. This study shows that temperature, which is socially regulated inside the hive, is a key factor that influences the ontogeny of circadian rhythmicity of workers.