Direct ingestion of plant sap from cut leaves by the leaf-cutting ants Atta cephalotes (L.) and acromyrmex octospinosus (reich) (Formicidae, Attini)

Abstract

Ingestion of radiolabelled plant juices from cut surfaces of leaves during foraging and during substrate preparation for the fungus garden was demonstrated for laboratory colonies of the leaf-cutting ants Atta cephalotes (L.) and Acromyrmex octospinosus (Reich). Using P32 isotope, up to one-third of the radioactivity in the leaves was taken in directly by the colony as a whole, but this was much less when C14 was used. Additional plant material was taken in by the ants via the fungus garden. Large numbers of ants spend time in investigating cut surfaces of leaves and also in cutting and crimping leaves. Ingestion of plant material during these processes could play an important nutritional role in the colony and this may explain why many ants return from foraging apparently unladen. Large ants obtained most of their plant juice intake during foraging and the medium and small ants took much of theirs during substrate preparation. Inhibitory chemicals did not affect cutting but they reduced drinking and also reduced the intake of P32 from leaves during substrate preparation. The ants also ingested different amounts of P32 from leaves of different acceptability. It is suggested that leaf-cutting ants use fungus culture as a means of ‘sidestepping’ plant inhibitors. Nutrients are ingested directly from leaves when these are palatable, and the less palatable components are made available to the ants via the fungus.

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

“…2 are similar, but only a single amylase substrate was used so that the latter enzyme activities had no error bars), the ants might have also already ingested and digested most of the starch using the a-amylases from their labial glands (D'Ettorre et al, 2002;Erthal et al, 2004;Erthal et al, 2007). This would be consistent with the notion that adult leafcutter ants also directly ingest plant sap and fruit juice (Littledyke and Cherrett, 1976) and would imply that the ants can extend this habit to any source of starch that is not contained in hard cell walls that their fungal symbiont needs to breach first. If excess starch would be processed in this way, the increased concentration of glucose might then affect the production of fungal amylase by some antinduced feedback mechanism (Silva et al, 2006a, b).…”

“…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).…”

Laccase detoxification mediates the nutritional alliance between leaf-cutting ants and fungus-garden symbionts

“…1 and 2B). An additional advantage of LgLcc1 ingestion may be that it helps neutralize phenolic compounds in plant sap that foraging workers may drink when cutting leaves (30).…”

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;.…”