Acetic Acid Vapour as a Resource and Stress in Drosophila

Acetic acid is utilized as a resource, to a threshold concentration where it becomes a metabolic stress, in Drosophila species of subgenera Drosophila and Sophophora that are normally collected by attraction to fermented-fruit baits. This is expected since ethanol is metabolized to acetic acid via acetaldehyde. There is a tendency among tropical species in these subgenera to have lower threshold concentrations for both ethanol and acetic acid than do temperate species. A similar trend is likely among populations within D. melanogaster. D. (Dorsilopha) busckii, however, hardly utilizes acetic acid, which may be a reflection of the dependence of this species upon vegetables and other resources that are quite exotic by comparison with other species attracted to fermented-fruit baits. In two species of subgenus Scaptodrosophila, D. inornata and D, hibisci, that are not attracted to fermented-fruit baits, acetic acid and ethanol are used to low levels (or not at all); the process of energy acquisition has yet to be explored in these species.