The infrabuccal pellet piles of fungus-growing ants

Abstract

Fungus-growing ants (Attini) live in an obligate mutualism with the fungi they cultivate for food. Because of the obligate nature of this relationship, the success of the ants is directly dependent on their ability to grow healthy fungus gardens. Attine ants have evolved com-plex disease management strategies to reduce theirgarden’s exposure to potential parasitic microbes, toprevent the establishment of infection in their gardens,and to remove infected garden sections. The infrabuccalpocket, a filtering device located in the oral cavity of allants, is an integral part of the mechanisms that leaf-cutterants use to prevent the invasion and spread of generalmicrobial parasites and the specific fungal-garden parasiteEscovopsis. Fungus-growing ants carefully groom theirgarden, collecting general debris and pathogenic spores ofEscovopsisin their infrabuccal pocket, the contents ofwhich are later expelled in dump chambers inside the nestor externally. In this study we examined how a phylogenetically diverse collection of attine ants treat their infrabuccal pellets. Unlike leaf-cutters that deposit their infrabuccal pellets directly in refuse piles, ants of themore basal attine lineages stack their infrabuccal pellets in piles located close to their gardens, and a separate caste of workers is devoted to the construction, management, and eventual disposal of these pile.