Impact of dietary treatments on longevity and body weight of Apis mellifera winter bees

In eusocial honey bees, Apis mellifera, diet, gut microbiota and nestmates
can all contribute to the health of freshly-emerged individual workers,
but their relative importance for longevity and body weight is currently
unknown. Here, we show that diet is most relevant, followed by gut
microbiota and the presence of nestmates. Freshly emerged workers were
randomly assigned to eight treatments (with or without honey/pollen,
protein-substitute lactalbumin, antibiotic tetracycline and nestmates for
24 h) and maintained under standardized laboratory conditions.
Longevity and food consumption were measured daily and fresh body weight
was assessed at day seven. The data show a significantly better survival
and a higher body weight in workers supplied with honey/pollen. Survival
was higher in the lactalbumin treatments compared to the ones restricted
to sucrose only, but lower compared to those with honey/pollen,
highlighting the importance of micronutrients. In contrast, antibiotic
treatment had a significant negative effect on longevity and body weight,
which may be explained by inactivated gut microbiota and/or toxicity of
the antibiotics. There was no positive effect of nestmates, probably due
to the short exposure period. In contrast, nestmates showed a negative
effect on survival in antibiotic-treated workers, possibly by transmitting
pathogens and antibiotic-induced gut dysbiosis. In conclusion, a macro-
and micronutrient-rich diet appears to be the key to individual honey bee
worker health. Providing an optimal diet and possibly gut microbiota
appears to be a promising way to promote managed A. mellifera
health.