Identification of Glutamic Acid as a Host Marking Pheromone of the African Fruit Fly Species Ceratitis rosa (Diptera: Tephritidae).

Host marking pheromones (HMPs) deposited by female fruit flies deter other females from overexploiting the same fruit for egg laying. Using a bioassay-guided approach, we identified the HMP of the Natal fruit fly species Ceratitis rosa as glutamic acid, 1, from the aqueous fecal matter extract of ovipositing females by liquid chromatography-quadrupole time-of-flight-mass spectrometry (LC-QTOF-MS). Dual choice oviposition assays showed that both the fecal matter extract and 1 significantly reduced oviposition responses in conspecific females of C. rosa. Glutamic acid levels were 10-20 times higher in fecal matter than in the ovipositor or hemolymph extracts of females. Identification of 1 as a host marking pheromone in females of C. rosa improves our understanding of fruit fly chemical ecology and provides evidence that it could be used as a potential component in the integrated management of this fruit fly species.

Identification of the Ubiquitous Antioxidant Tripeptide Glutathione as a Fruit Fly Semiochemical.

Many insects mark their oviposition sites with a host marking pheromone (HMP) to deter other females from overexploiting these sites. Previous studies have identified and used HMPs to manage certain fruit fly species; however, few are known for African indigenous fruit flies. The HMP of the African fruit fly, Ceratitis cosyra, was identified as the ubiquitous plant and animal antioxidant tripeptide, glutathione (GSH). GSH was isolated from the aqueous extract of adult female fecal matter and characterized by LC-QTOF-MS. GSH level increased with increasing age of female fecal matter, with highest concentration detected from 2-week-old adult females. Additionally, GSH levels were 5-10-times higher in fecal matter than in the ovipositor or hemolymph extracts of females. In bioassays, synthetic GSH reduced oviposition responses in conspecifics of C. cosyra and the heterospecific species C. rosa, C. fasciventris, C. capitata, and Zeugodacus cucurbitae. These results represent the first report of a ubiquitous antioxidant as a semiochemical in insects and its potential use in fruit fly management.