Abstract:
Dietary sources of essential amino acids
(EAAs) are used for growth, somatic maintenance and
reproduction. Eusocial insect workers such as honeybees
are sterile, and unlike other animals, their nutritional needs
should be largely dictated by somatic demands that arise
from their role within the colony. Here, we investigated the
extent to which the dietary requirements of adult worker
honeybees for EAAs and carbohydrates are affected by
behavioural caste using the Geometric Framework for
nutrition. The nutritional optimum, or intake target (IT),
was determined by confining cohorts of 20 young bees or
foragers to liquid diets composed of specific proportions of
EAAs and sucrose. The IT of young, queenless bees shifted
from a proportion of EAAs-to-carbohydrates (EAA:C) of
1:50 towards 1:75 over a 2-week period, accompanied by a
reduced lifespan on diets high in EAAs. Foragers required
a diet high in carbohydrates (1:250) and also had low survival on diets high in EAA. Workers exposed to queen
mandibular pheromone lived longer on diets high in EAA,
even when those diets contained 59 their dietary requirements.
Our data show that worker honeybees prioritize
their intake of carbohydrates over dietary EAAs, even
when overeating EAAs to obtain sufficient carbohydrates
results in a shorter lifespan. Thus, our data demonstrate that
even when young bees are not nursing brood and foragers
are not flying, their nutritional needs shift towards a diet
largely composed of carbohydrates when they make the
transition from within-hive duties to foraging.
