Submitted to: Green Chemistry Letters and Reviews
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/18/2009
Publication Date: 12/31/2008
Citation: Walse, S.S., Alborn, H.T., Teal, P.E. 2008. Environmentally Regulated Abiotic Release of Volatile Pheromones from the Sugar-based Oral Secretions of Caribflies. Green Chemistry Letters and Reviews. 1(4):205-217. Interpretive Summary: It is highly probable that many species of insect pests, or at least Tephritids, utilize a disconnect between abiotic and biotic mechanisms of pheromone release to initiate aggregation. Consequently, the characterization and exploitation of these natural abiotic mechanisms has marked potential for improving the utility of semiochemical-based pest management practices as “green” alternatives to insecticide application. Specifically, we report a natural mechanism for abiotic pheromone release that is used by Male Anastrepha suspensa [Loew] (caribflies) to mark mating sites on leaf surfaces; results show that pheromone release from the markings occurs over many days with a periodicity that parallels relative humidity and complements the daily pattern of the caribflies’ reproductive activity. In more general context, however, this mechanistic study illustrates connectivity between the abiotic environmental processing of chemical signals and physicochemical-based inter-organism communication strategies; it implies that their simultaneous investigation can be mutually beneficial and contributes to an understanding of how biologically active molecules can transmit efficiently through the environment.
Technical Abstract: We report an abiotic mechanism for the emission of volatile insect pheromones that is controlled by environmentally-induced change in the physicochemical properties of the sugar-based release matrix. Male Anastrepha suspensa [Loew] (caribflies) mark mating sites on leaf surfaces by depositing oral secretions that contain sugar, as well as, gamma-hydroxy acid and gamma-lactone forms of the diastereomeric aggregation pheromones, epianastrephin and anastrephin. The gamma-hydroxy acids extend emission over many days via aqueous equilibrium with the thermodynamically less preferred, but more volatile, gamma-lactones (~100:1). A kinetic model, which supports a gamma-lactone diffusion-limited rate, was generated and tested by measuring the effect of temperature and humidity under fixed and ambient inputs, respectively. Results show that pheromone release from the markings occurs with a periodicity that parallels relative humidity and complements the daily pattern of the caribflies’ reproductive activity. This study provides an example of a physicochemical-based inter-organism communication strategy that has been mechanistically linked to the abiotic environmental processing of volatile chemical signals. The exploitation of this natural connectivity will spur environmentally sustainable chemistries, particularly pheromone-based alternatives to insecticide application.