Seminal fluids and its role in modulating female - Reproductive behaviour

Sexual conflict may drive the evolution of molecules in the male accessory gland and ejaculatory duct fluid (AGF and EDF) that manipulate female reproductive activity in insects. The aim of this study was to demonstrate experimentally that these molecules directly influence female re-mating decisions in the Queensland fruit fly Bactrocera tryoni, and determine the mechanisms underlying this phenomenon. Injections of AGF and EDF into virgin females showed that the inhibitory effect on remating is dose dependent. Post mating experiments revealed that accessory gland contents replenish over 22 hours, and that the newly synthesized molecules are potent at inhibiting remating. These AGF and EDF molecules, which influence female behaviour and physiology typically, appear to pass through the wall of the tract into the haemocoel. With the help of radioactive labelling, (using L-[35S] methionine and cysteine) we determined the fate of these seminal fluid molecules in female B. tryoni. We found that these seminal fluid molecules travel through the female body and are predominantly found in the head and thorax. The study of these seminal fluid molecules may provide novel methods of insect control, especially in Bactrocera tryoni, which is Australia's most costly horticultural pest.