Functional morphology of the Dufour gland in the queenless ant Dinoponera quadriceps

Abstract

Colonies of the queenless ponerine ant Dinoponera quadriceps are characterized by a social hierarchy among the workers, in which the gamergate occupies the alpha rank. She may be challenged, however, by a beta worker in an attempt to take over reproductive control in the colony. The gamergate does not engage in a direct conflict, however, but only smears secretion from her Dufour gland onto the beta worker. This secretion then stimulates the low-ranked workers to immobilize the beta worker and thus prevent it from overthrowing the gamergate. Our histological and ultrastructural examination of the Dufour gland in gamergates, one-week-old workers that still have reproductive potential and low-ranked foragers clearly shows that the gamergate has the most developed gland containing secretory cells displaying abundant smooth endoplasmic reticulum and an obvious microvillar differentiation of the apical cell membrane. These findings are in line with the already existing chemical and behavioral observations of the peculiar pretender punishment in this species.