Haemolymph sugar levels in a nectar-feeding ant: dependence on metabolic expenditure and carbohydrates deprivation

SCHILMAN, P.E. & ROCES, F.

JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY

Springer Verlag

Lugar: New York, USA; Año: 2008 vol. 178 p. 157 - 165

0174-1578

In nectar-feeding insects, sugars are an important source of fuel and serve as energy storage for future demands. In the present study, we analyzed the haemolymph sugar levels in foragers of the ant Camponotus rufipes trained to collect nectar from an artificial feeder, and their dependence on the metabolic rate of the individuals, measured as their CO2 production rates during voluntary feeding. Haemolymph sugar levels were measured by high-pressure liquid chromatography (HPLC). As in many insect species, the levels of sugars in the haemolymph of C. rufipes were variable, with trehalose as the main sugar followed by glucose and traces of fructose and sucrose. In foraging ants, trehalose level was independent of the worker’s locomotory activity and metabolic rate while feeding. Carbohydrate deprivation of the colony had a strong effect on the haemolymph sugar levels of non-foraging ant workers, with a significant decrease in trehalose and glucose with increasing starvation. We also found a correlation between haemolymph sugar levels and behavioral states in non-foraging ants, with immobile workers having higher trehalose and fructose levels than active ones. It is suggested that under food deprivation, inside-nest workers initially stay completely immobile as a strategy to save energy, and only become active and start to search for food when the trehalose levels decrease even more. Based on a conservative estimation, well-fed ant would have been able to travel up to 500 m, or to maintain moderate locomotory activity for longer than 10 hours, using only the energy reserves provided by the haemolymph trehalose, before reaching the levels found in starved nest-mates.