The role of fungus in the diet of the leaf‐cutting ant Atta cephalotes (L.)

Abstract

Abstract. 1. The workers and queen of the leaf‐cutting ant Atta cephalotes fed on the juice of swollen hyphae (staphylae) produced by their cultivated fungus, but neither obtained sufficient energy from this source for their respiratory needs. The number of staphylae eaten by workers increased with worker size but was not enough to satisfy their energy requirements.2. Larvae fed on whole staphylae and staphylae previously chewed by workers, and obtained sufficient energy from this source for respiration and growth. No evidence of feeding on fungus hyphae or of trophallaxis between worker and larvae was found. Larvae preferred staphylae to hyphae when fed them artificially and they gained more weight on the former.3. Worker ants imbibed plant sap during the preparation of plant material for the fungus garden and the uptake of carbohydrate during this process was sufficient to supply their energy needs for approximately 24 h.4. Staphylae were richer in lipid and carbohydrate, and poorer in protein than ant fungal hyphae.5. The number of staphylae produced by the fungus gardens of two small nests was comparable with the observed consumption rate but would provide only about 4% of the nest's respiratory requirements.6. In the light of these findings, a revised view of the role of the fungus in the diet of the ant is discussed.

Symbiotic adaptations in the fungal cultivar of leaf-cutting ants

“…Scattered observations of gongylidia in lower-attine fungus gardens suggests that gongylidia-like structures may have evolved several times 37 , but it was only when the fungal cultivar became obligate 20-25 MYA that gongylidia became synamoporphic for all higher-attine (including leaf-cutting) ant fungus gardens. Their functional significance for nutritional provisioning was confirmed more than 30 years ago, and around the same time it was discovered that fungal enzymes are transferred via the ant faecal fluid 13,17 . However, the coevolutionary processes that shaped and maintained these fungal organs have only recently regained focal attention, confirming and expanding the results by Boyd and Martin 17 for a number of fungal enzymes [19][20][21] .…”

“…1c) 11,12 . Relative to fungal hyphae, the gongylidia have high concentrations of lipids and carbohydrates (free sugars and polysaccharides) and provide all food for the ant larvae and most food for the adult ants 13 . Based on comparisons of extant species, the evolution of gongylidia coincided with distinct changes in fungus garden enzyme activity 14 , proportional shifts in plant material used as fungal substrate 15 and the cultivated fungi loosing the ability to live independently without the ants 10 .…”

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

“…The mutualism is obligatory for both the symbiotic fungus and the ants (Mueller et al, 2005), as the fungus is dependent on the ants for substrate provisioning and control of competing and pathogenic microbes (Currie et al, 1999;Hart et al, 2002;Valmir Santos et al, 2004), whereas the ants are dependent on the fungus as their main food component (Weber, 1966;Littledyke and Cherrett, 1976;Quinlan and Cherrett, 1979).…”

Mutualistic bacteria and a possible trade-off between alternative defence mechanisms in Acromyrmex leaf-cutting ants

“…The fungus is an essential food source for the ants (Quinlan and Cherrett, 1977;Hölldobler and Wilson, 1990). Ant brood is fed exclusively with fungal hyphae and gongylidia, special fungal cells containing nutrients, whereas adult ants get additional sugars from plant sap (Littledyke and Cherrett, 1976;Quinlan and Cherrett, 1979). The ants provide the fungus with nutrition and play an essential role in protecting the cultivar from parasites and competitors, which rapidly overgrow fungus gardens when ant-care is absent (Weber, 1972;Currie et al, 1999 b;.…”