The role of substrate preparation in the symbiosis between the leaf‐cutting ant Acromyrmex octospinosus (Reich) and its food fungus

Abstract

Abstract. 1. In laboratory nests the ants thoroughly licked leaf fragments by a rasping action of their glossa before inoculating the food fungus. The extent of this licking varied with the substrate and was influenced by the thickness of surface leaf waxes and by the chemical attractiveness of the substrate. 2. Microscopy and wettability studies showed that licking removes the wax layer present on leaves. It also removes or inhibits micro‐organisms present. 3. Chemically de‐waxed and decontaminated leaves and ant‐licked leaves proved the best substrates for artificially culturing the ant fungus. 4. The process of substrate preparation circumvents some of the normal defence mechanisms of green plants against fungal attack. The ant fungus thus utilizes nutritionally richer resources of green leaves normally available only to specialized parasitic fungi, rather than the nutritionally inferior shed leaves normally available to saprophytic fungi.

Rapid shifts in Atta cephalotes fungus-garden enzyme activity after a change in fungal substrate (Attini, Formicidae)

“…Atta and Acromyrmex workers carry freshly cut leaves to the nest where they process this material into substrate for their crop symbiont Leucocoprinus gongylophorus, by chewing it into minute pieces that are mixed with ''saliva''. These leaf pieces are deposited on the outer edges of the top section of the garden, after which fragments of mycelium are added, together with fecal fluid that contains fungal enzymes that have survived gut passage, to assist with initial substrate degradation (Boyd and Martin, 1975;Quinlan and Cherrett, 1977;Bass and Cherrett, 1994;Erthal et al, 2009). While the fungus garden degrades this plant material, it eventually produces inflated hyphal tips (gongylidia) that are preferentially eaten by the ants before the old mycelium is removed from the bottom sections of the garden (Bass and Cherrett, 1995;Schiøtt et al, 2008).…”

Symbiont recognition of mutualistic bacteria by Acromyrmex leaf-cutting ants

“…In addition to providing substrate for its growth, the ants weed and groom their fungus garden to remove competing microbes or pathogens (Quinlan and Cherrett, 1977;Currie and Stuart, 2001), especially Escovopsis -a specialized microparasite capable of rapidly devastating the entire fungus garden (Currie et al, 1999a;Currie and Stuart, 2001). Besides engaging in specific behaviors to defend their fungus gardens, the ants have a mutualism with bacteria that produce antibiotics with apparent specific activity against Escovopsis ( Currie et al, 1999bCurrie et al, , 2003a.…”

Reduced biological control and enhanced chemical pest management in the evolution of fungus farming in ants

“…Exocrine gland secretions, especially from the metapleural glands (MG), are broadspectrum antimicrobials (do Nascimento et al 1996;Bot et al 2002;Fernández-Marín et al 2006). In short, ants reduce the pathogen load within nests by (i) monitoring contaminant levels ( Fernández-Marín et al 2006), (ii) grooming their bodies and those of adult and immature nest-mates (Bailey 1920;Weber 1972;Quinlan & Cherrett 1977), (iii) actively regulating antimicrobials from exocrine glands ( Fernández-Marín et al 2006), (iv) weeding the garden (Bass & Cherrett 1994;Currie et al 2006), and (v) deploying antibiotics from Pseudonocardia (Currie et al 1999aLittle et al 2006).…”