Effect of past and present behavioural specialization on brain levels of biogenic amines in workers of the red wood ant Formica polyctena

Abstract

Social insect workers usually participate first in intranidal tasks (i.e. act as nurses within the nest) and then switch to extranidal tasks and become foragers. However, foragers sometimes switch back again to brood care and become reverted nurses. Behavioural and physiological correlates of the transition nurse-forager (behavioural maturation) and forager-reverted nurse (behavioural reversion) are relatively well known in the honeybee, although they are less explored in ants. To understand better the role of biogenic amines in ant behavioural maturation and behavioural reversion, the levels of octopamine (OA), dopamine (DA) and serotonin (5-HT) are examined in the brains of nurses, foragers and reverted nurses of the red wood ant Formica polyctena Först. (Hymenoptera: Formicidae). Brain OA levels and the ratios OA : DA and OA : 5-HT are higher in nurses than in foragers and reverted nurses. Reverted nurses and foragers do not differ significantly with respect to brain biogenic amine levels and amine ratios. Biogenic amine levels in brains of workers of F. polyctena are thus maturation-related rather than task-related. This is one of the first studies of neurochemical correlates of ant behavioural maturation and the first attempt to identify neurobiological correlates of ant behavioural reversion. The data obtained provide further evidence that neurobiological processes underlying honeybee and ant behavioural maturation and behavioural reversion reveal important differences.

Social dominance and reproductive differentiation mediated by dopaminergic signaling in a queenless ant

“…For example, brain octopamine levels are elevated in old honeybee workers to trigger foraging behavior (Shultz and Robinson, 2001). The age-dependent changes in brain amine levels are also observed in ants, implying that age-dependent transition of amine levels commonly occur in social Hymenoptera (Seid and Traniello, 2005;Seid et al, 2008;Wnuk et al, 2011).…”

“…Age-dependent increases of brain amine levels have been reported in workers of various social insects, implying strong links between biogenic amine and age-dependent worker polyethism (Schultz andRobinson, 1999, 2001;Seid and Traniello, 2005;Seid et al, 2008; but see Wnuk et al, 2011). In Diacamma, workers specialize in insidenest tasks for 1-2 months after eclosion (Nakata, 1995); thus, day-7 workers are still nurses.…”

“…Another difficulty comes from the pleiotropic functions of biogenic amines. Brain amine levels are also associated with worker division of labor and amine levels tend to be age dependent (Schultz andRobinson, 1999, 2001;Seid and Traniello, 2005;Seid et al, 2008;Wnuk et al, 2011). As age is also a major determinant of dominance rank (Strassmann and Meyer, 1983;Higashi et al, 1994;Monnin and Ratnieks, 1999;Tsuji and Tsuji, 2005), brain amine levels may be under complex regulation by age and dominance rank (Cuvillier-Hot and Lenoir, 2006).…”

Neurohormonal changes associated with ritualized combat and the formation of a reproductive hierarchy in the antHarpegnathos saltator

“…In addition to reproduction and dominance, biogenic amines affect differences in task performance among non-reproductive workers Seid et al, 2008;Seid and Traniello, 2005;Wagener-Hulme et al, 1999;Wnuk et al, 2011). Workers generally display an age-based polyethism, where young workers perform in-nest duties while older workers transition to outside tasks, such as nest defense and foraging.…”

Octopaminergic system in the brain controls aggressive motivation in the ant,Formica Japonica

“…In general, the number of tasks performed by workers increase and change depending on their age in ants. However, there still remains plasticity in shifting between different tasks according to the demand of colony, for example, between nursing and foraging [12], foraging and nest building (our observation). However, at this stage, little is understood neuronal mechanisms how they change their task and which social demand in the colony makes workers change their task.…”