Mandibles of Leaf-Cutting Ants: Morphology Related to Food Preference

Abstract

Feed adaptation is crucial for the ecological success of animals, which explore specific or varied resources according to the suitability of the selected feature. We hypothesized that the mandibles of leaf-cutting ants exhibit a greater degree of specialization because of the specific food preference of some species. The objective of this study was to highlight possible morphological differences between the mandibles of leaf-cutting ants of the genus Atta related to the food preference of the species, i.e., to investigate the morphofunctionality of mandibles in conjunction with a study of the leaf anatomy of plants selected. A detailed description of the mandibles of workers of the grass-cutting ant Atta bisphaerica and of the leaf-cutting ant Atta sexdens rubropilosa was provided, and the anatomy and chemical composition of the plant material foraged by these species were investigated. For morphometric analysis, 50 individuals of each of the four size classes were dissected for removal of the right mandible and one sample of each caste was processed for scanning electron microscopy. The Atta species had a similar mandibular morphology and differences were only observed between species and among castes, demonstrating the clear specialization of workers. Together with the anatomical study of the foraged plant material, the results indicate a high abundance of lignified cells in grasses, permitting to infer that the foraging and processing of these plants can lead to differences in behavioral acts during their preparation and incorporation in the fungus garden. We accept the hypothesis of morphofunctionality in view of the mandibular morphology observed.