Male sexual competitiveness of two Ceratitis capitata strains, tsl Vienna 8 and OX3864A transgenics, in field cage conditions

Abstract

AbstractThe success of the sterile insect technique (SIT) depends on the ability of sterile males to compete effectively with wild males to mate with wild females. This study compared the sexual competitiveness and other behavioral parameters of males of two strains of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), tsl Vienna 8 (tsl V‐8) and the transgenic line OX3864A, in competition with wild males from the São Francisco Valley region in Bahia, Brazil. Mating events were observed in field cages containing virgin, sexually mature insects as follows: 50 wild females (10–12 days old), 50 wild males (8–10 days old), and either 50 tsl V‐8 sterile males (5 days old) or 50 transgenic males (3–4 days old). In addition to scoring male type for each mating event, we also monitored the location of mating events within the tree canopy, mating duration, and mating latency. The proportion of females that mated did not differ between the two competition scenarios tested (tsl V‐8 vs. wild males: 0.65 ± 0.04; transgenic vs. wild males: 0.64 ± 0.03). Relative sterility index did not differ between sterile (0.34 ± 0.04) and transgenic males (0.31 ± 0.03). The latency period was significantly longer for transgenic males (84.90 ± 4.87 min) than for sterile (65.24 ± 4.65 min) and wild males (66.61 ± 2.66 min). Mating events involving the three strains occurred in the same area of the tree, i.e., mid‐height, in the central sector and on leaf undersurfaces. The mean duration of mating events involving sterile (94.1 ± 3.59 min) and transgenic males (81.1 ± 3.54 min) were both significantly shorter than for wild males (123.3 ± 1.93 min). Further investigation is suggested to assess other behavioral parameters, such as the amount of sperm transferred by transgenic males, their ability to disperse and survive in the field conditions, and their capacity to prevent females remating with wild males, in order to determine the potential of this transgenic strain for inclusion in the Brazilian SIT programs.