Anatomy and histology of the metapleural gland in the giant tropical ant Paraponera clavata (Fabricius, 1775) (Formicidae: Paraponerinae)

Abstract

Ants are social insects with about 85 exocrine glands with different morphologies. The metapleural gland is exclusive to ants and its compounds have antimicrobial action, indicating a function in the defense against pathogens. Within ants, Paraponera clavata is the only living species representative of Paraponerinae. This study describes the anatomy and histology of the metapleural gland in workers of P. clavata. The metapleural gland is formed by secretory units that release secretion in a reservoir through collecting canaliculi. Secretory units are bicellular with a well-developed globular secretory cell, with 145 µm in diameter, and a duct cell forming the collecting canaliculi characterizing a class III gland. The metapleural gland is pointed out as a synapomorphy of ants. Paraponerinae constitutes one of the six subfamilies of the basal and paraphyletic Poneroide clade and knowledge of the metapleural gland morphology contribute to the understanding of evolutionary history of the basal ants' groups.