Behavioral changes mediated by hunger in honeybees infected withNosema ceranae

Abstract

The microsporidian Nosema is a common honeybee pathogen which enters the adult bee orally and multiplies in its gut, imposing a metabolic demand on its host. The newly discovered Nosema ceranae, given its relatively new association with the European honeybee, is likely to be particularly severe in this regard. We therefore hypothesized that N. ceranae exerts a significant effect on the feeding behavior of infected bees. Results from our experiments support this idea, revealing that infected bees are more responsive to sucrose and are less inclined to share this food with other bees, suggesting that they have a higher hunger level. We argue that increased hunger in the host is a general physiological effect of a number of pathogenic infections and due to its effect on host behavior could act as a mechanism by which the host and the pathogen can influence the transmission rates of an infection. Behavioral mechanisms, mediated by physiology could therefore be in the frontline of any arms race between a host and its pathogen.

Nosema spp. infections cause no energetic stress in tolerant honeybees

“…Although this would indicate increased hunger in those honeybees, Nosema-infected workers did not consume more food despite increased mortality (Williams et al, 2014). However, decreased trophallaxis (food sharing) in Nosema-infected honeybees (Naug & Gibbs, 2009), suggests that energetically stressed honeybees are not likely to share food with their nest mates. Instead, Nosema-infected honeybees actually leave the hive energetically stressed (Mayack & Naug, 2010) and may not return (Wolf et al, 2014).…”

Covert deformed wing virus infections have long-term deleterious effects on honeybee foraging and survival

“…Given that our donor bees all came from a single, rare uninfected colony, we had a priori not expected any large variation in the impact of the virus. Possible reasons for this variation could be linked with seasonal factors, variation in the genetic compatibility with the host colonies, or subtle differences in the performance or health of the host colonies, such as the possible presence of Nosema among the host workers, which we did not explicitly look at, but which is known to cause precocious foraging and affect longevity, activity and out-of-hive performance of honeybees [13,45,58,76,77]. Alternatively, it is possible that the variation in DWV impact is linked to some of the control bees having become infected during the later stages of our experiment, which our treatment validation results suggest may have been the case (though likely at lower levels, figure 2), and that the speed at which this occurred differed across host colonies.…”

Honey bee colonies provided with natural forage have lower pathogen loads and higher overwinter survival than those fed protein supplements

“…Nutritional stress is exacerbated when there is Nosema infection because this microsporidia relies on the host to furnish energy for growth and reproduction (Mayack and Naug 2009;Martín-Hernández et al 2011;Holt et al 2013). Queen loss might also be more common because infected workers are less likely to feed nestmates (Naug and Gibbs 2009). In our study, colonies fed diet 1 had the greatest incidence of Nosema and the highest queen losses.…”