Abstract:
Over-consuming amino acids is associated with reduced survival in many species, including honeybees.
The mechanisms responsible for this are unclear but one possibility is that excessive intake of amino
acids increases oxidative damage. If this is the case, antioxidant supplementation may help reduce the
survival costs of high amino acid intake. We tested this hypothesis in African honeybees (Apis mellifera
scutellata) using the major antioxidant in green tea, epigallocatechin-3-gallate (EGCG). We first determined
the dose-range of EGCG that improved survival of caged honeybees fed sucrose solution. We then
provided bees with eight diets that differed in their ratio of essential amino acids (EAA) to carbohydrate
(C) (0:1, 1:250, 1:100, 1:75, 1:50, 1:25, 1:10, 1:5 EAA:C) and also in their EGCG dose (0.0 or 0.4 mM). We
found that bees fed sucrose only solution survived better than bees fed EAA diets. Despite this, bees preferred
a diet that contained intermediate ratios of EAA:C (ca. 1:25), which may represent the high
demands for nitrogen of developing nurse bees. EGCG supplementation improved honeybee survival
but only at an intermediate dose (0.3–0.5 mM) and in bees fed low EAA diets (1:250, 1:100 EAA:C). That
EGCG counteracted the lifespan reducing effects of eating low EAA diets suggests that oxidative damage
may be involved in the association between EAAs and lifespan in honeybees. However, that EGCG had no
effect on survival in bees fed high EAA diets suggests that there are other physiological costs of over-consuming
EAAs in honeybees.
