Morphology and Volatilomics of the Pre-Pharyngeal and Pharyngeal Glands of Paraponera clavata (Hymenoptera: Paraponerinae) and Pachycondyla crassinoda (Hymenoptera: Ponerinae) Workers

Abstract

Ants occur in a remarkable diversity of species, many of which fulfill essential ecological roles and exhibit complex eusocial behaviors. Among their unique adaptations are specialized exocrine glands, such as the pre-pharyngeal and pharyngeal glands, which produce secretions crucial for physiology and social cohesion. Despite their importance, these glands are poorly studied in Paraponerinae and Ponerinae species. This study examines the morphology and chemical composition of these glands in workers of Paraponera clavata (Paraponerinae) and Pachycondyla crassinoda (Ponerinae). The results document distinct morphological and morphometric differences: the pre-pharyngeal gland in P. clavata is larger, with cells rich in proteins and glycoproteins, whereas in P. crassinoda, the gland has more extensive secretory cells and a higher concentration of lipids. Additionally, the pharyngeal glands in P. clavata are tubular, while in P. crassinoda, they have large lobes with internal cuticular projections. Chemical analyses identified shared hydrocarbons between the species, as well as unique compounds that may reflect specific behavioral and ecological adaptations. These findings suggest that morphological and chemical differences in these ants' glands are potentially associated with dietary habits and behavioral traits.