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

Feeding adaptation is crucial for the ecological success of animals, which explore specific or varied resources according to the suitability of the selected morphological feature. We hypothesized that the mandibles of leaf-cutting ants exhibit a 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 ant species of the genus Atta related to food preference, i.e., to investigate the morphofunctionality. 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. For morphometric analysis, 50 individuals of four size classes were dissected for removal of the right mandible and one sample of each caste was processed for scanning electron microscopy. It was observed differences between species and among castes, demonstrating the clear specialization of workers. Although the results of mandibular morphometry accept the hypothesis of morphofunctionality, further investigation is needed taking into consideration the body size of foragers, robustness and factors that confer greater resistance to the mandibles such as zinc content, the force employed during cutting, and mandibular biomechanics.