Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus.
BACKGROUND
Leaf-cutting ants collect plant fresh material for the cultivation of their mutualistic fungus. Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) cause great economic losses through their foraging activity, mainly in agriculture. The main control method is the application of granulated toxic baits incorporated with an active ingredient (AI). The present goal is to evaluate the effect of caffeine on in vitro growth of the mutualistic fungus and on the survival of the leaf-cutting ants, aiming to verify the potential toxicity of this secondary metabolite over these organisms.


RESULTS
Three distinct patterns of fungal growth correlated with caffeine concentration were observed: (1) no effect (0.01% caffeine); (2) intermediate growth reduction (0.05% caffeine); (3) drastic growth reduction (0.10 and 0.50% caffeine). The highest caffeine concentration causes fungus death in the first week. As for insect survival, caffeine does not seem to exert any effect. The treatments with diet containing caffeine showed similar values of M50, irrespective of caffeine concentration.


CONCLUSIONS
As caffeine was shown to reduce growth of the mutualistic fungus of Atta sexdens rubropilosa, but with no conclusive effect on insect survival, a hypothetical explanation for the selection of different Coffea species by this leaf-cutting ant species might be associated with caffeine toxicity to the fungus.
Department of Botany, Institute of Bioscience, University of São Paulo, São Paulo, Brazil.
Carlos H
CH
Miyashira
Daniel G
DG
Tanigushi
Adriana M
AM
Gugliotta
Déborah Y A C
DY
Santos
D000818:Animals; D001000:Ants / Q000187:drug effects* / Q000254:growth & development / Q000382:microbiology*; D002110:Caffeine / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005658:Fungi / Q000187:drug effects*; D016019:Survival Analysis; D013559:Symbiosis
D002110:Caffeine