Neuro-endocrine correlates of ovarian development and egg-laying behaviors in the primitively eusocial wasp (Polistes chinensis).

To explore the roles of biogenic amines in reproduction in workers in primitively eusocial societies, correlations between brain levels of biogenic amines and ovarian development or oviposition in workers of the paper wasp Polistes chinensis were investigated. Several workers in queenright colonies developed ovaries and were potential egg-layers. Maximum ovarian width was significantly correlated with brain levels of dopamine, serotonin and their metabolites (N-acetyldopamine and N-acetylserotonin). Individuals with developed ovaries proceeded with yolk formation had significantly higher levels of brain dopamine, serotonin and N-acetyldopamine compared with individuals with undeveloped ovaries. Brain dopamine levels were higher in egg-laying individuals than in other individuals with developed ovaries. Thus, the workers of the paper wasp showed quantitative differences in brain dopamine levels correlated with reproduction. These results suggest that the brain levels of biogenic amines in paper wasp workers correspond to their tasks, and that there is a mechanism for promoting reproduction by dopamine, as previously reported in the workers of eusocial bees.