Octopamine mobilizes lipids from honey bee (Apis mellifera) hypopharyngeal glands

Abstract

Recent widespread honey bee (Apis mellifera) colony loss is attributed to a variety of stressors, including parasites, pathogens, pesticides and poor nutrition. In principle, we can reduce stressinduced declines in colony health by either removing the stressor or increasing the bees' tolerance to the stressor. This latter option requires a better understanding than we currently have of how honey bees respond to stress. Here, we investigated how octopamine, a stress-induced hormone that mediates invertebrate physiology and behavior, influences the health of young nurse-aged bees. Specifically, we asked whether octopamine induces abdominal lipid and hypopharyngeal gland (HG) degradation, two physiological traits of stressed nurse bees. Nurse-aged workers were treated topically with octopamine and their abdominal lipid content, HG size and HG autophagic gene expression were measured. Hemolymph lipid titer was measured to determine whether tissue degradation was associated with the release of nutrients from these tissues into the hemolymph. The HGs of octopamine-treated bees were smaller than control bees and had higher levels of HG autophagy gene expression. Octopamine-treated bees also had higher levels of hemolymph lipid compared with control bees. Abdominal lipids did not change in response to octopamine. Our findings support the hypothesis that the HGs are a rich source of stored energy that can be mobilized during periods of stress.

Adipokinetic hormone (AKH), energy budget and their effect on feeding and gustatory processes of foraging honey bees

“…In honey bee nurses, which are the younger bees in the colony, topical application of octopamine leads to a reduction of the hypopharyngeal glands and a concomitant increase in the levels of hemolymph lipids compared with control bees. In contrast, abdominal lipids did not change in response to octopamine treatment 77 . These results indicate that the octopaminergic pathway has the capacity to mobilize nutrients stored in the hypopharyngeal grands, at least in nurse bees, which is considered as a response to stress 77 .…”

“…In contrast, abdominal lipids did not change in response to octopamine treatment 77 . These results indicate that the octopaminergic pathway has the capacity to mobilize nutrients stored in the hypopharyngeal grands, at least in nurse bees, which is considered as a response to stress 77 . Whether the same results are obtained in foragers, for which octopaminergic signalling plays a substantial role in reward representation 78 , 79 , remains to be determined.…”

“…While AKH seems to have lost its original function in honey bee foragers, the capacity of the insulin/AKH system to mobilize nutrient stores depends on the age and caste considered as well as on the season of the year. This system may thus be relevant for the regulation of the division of labor 71 , and may involve additional mechanisms such as octopaminergic signalling 77 . In honey bee nurses, which are the younger bees in the colony, topical application of octopamine leads to a reduction of the hypopharyngeal glands and a concomitant increase in the levels of hemolymph lipids compared with control bees.…”

Propolis Extract and Chitosan Improve Health of Nosema ceranae Infected Giant Honey Bees, Apis dorsata Fabricius, 1793

“…Although infected bees do not exhibit obvious external disease symptoms, some of the main pathophysiological effects from an infection identified from omics studies have pointed to metabolic dysregulation [ 18 , 21 , 25 , 69 ]. Resulting from this metabolic dysregulation are the key symptoms of infection, which are lowered trehalose levels and reduced hypopharyngeal glands [ 22 , 24 , 62 ]. Therefore, we find that the measures used in this study to be accurate predictors of bee health and recovery from a N. ceranae infection.…”

“…Nosemosis is considered to be a chronic infection that does not exhibit obvious external disease symptoms, but can cause a poor nutrient and energy absorption leading to a suppressed immune function and ultimately a shortened life span [ 17 , 18 , 19 , 20 , 21 ]. Infected bees have evidence of lower trehalose and lipid levels, and a reduced hypopharyngeal gland resulting from the poor nutrient absorption across the gut lining [ 22 , 23 , 24 ]. N. ceranae primarily lives and reproduces in the gut lining which is likely the cause for the poor nutrient absorption in infected bees [ 25 , 26 ].…”