A fluorescent sperm-specific marker for the medfly, Ceratitis capitata.

The medfly, Ceratitis capitata (Diptera: Tephritidae) is an invasive pest species of agricultural importance. Its polyphagous behavior and its high reproductive capacity are responsible for the spread of this species in the last two centuries from sub-Saharan Africa to several tropical and sub-tropical regions worldwide. The environmental-friendly Sterile Insect Technique (SIT) has been effectively applied as a component of area-wide integrated pest management (AW-IPM) for C. capitata since the 1970s. Effective monitoring to assess the number and mating success of the released medflies is essential. Using a transgenic approach we developed a direct sperm visualization system which makes it possible to follow the fate of sperm from different males in the female reproductive tract of the medfly. For this purpose, we generated a sperm-specific marking system based on the spermatogenesis-specific C. capitata beta2-tubulin (Ccbeta2t) promoter driving the expression of the reporter genes GFP or DsRed. Monitoring of the mating success of sterile released males by trapping females and examining their spermathecae is possible with these strains. Moreover, the availability of differently sperm-marked lines will help us to understand the relationship between sperm allocation, remating frequency and sperm displacement in the medfly, given that in wild populations females can remate with a strong paternity skew. In preliminary laboratory competitiveness assays we determined that the marker does not cause general fitness disadvantages. Therefore, such harmless transgenic markers represent an ideal springboard to transfer insect transgenesis technology from the laboratory to field applications.