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

Abstract

The 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 AE 0.04; transgenic vs. wild males: 0.64 AE 0.03). Relative sterility index did not differ between sterile (0.34 AE 0.04) and transgenic males (0.31 AE 0.03). The latency period was significantly longer for transgenic males (84.90 AE 4.87 min) than for sterile (65.24 AE 4.65 min) and wild males (66.61 AE 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 AE 3.59 min) and transgenic males (81.1 AE 3.54 min) were both significantly shorter than for wild males (123.3 AE 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.

Radiation effects on Drosophila suzukii (Diptera: Drosophilidae) reproductive behaviour

“…Our data showed that male condition did not influence mating latency period; however, sterile females presented a longer mating latency compared to fertile females. Effects of irradiation on latency were previously reported in males of B. cucurbitae, B. tryoni and C. capitata, but not in females (Haq et al, 2013;Radhakrishnan et al, 2009;Virginio et al, 2017). According to Cayol, Vilardi, Rial, and Vera (1999), mating latency is controlled by females and not by males.…”

“…The female condition of D. suzukii did not have an effect on mating duration, but sterile males differ from fertile males in the duration of copula. Shorter copulation when sterile males are involved was already reported for A. serpentina, A. fraterculus and C. capitata (Allinghi et al, 2007;Cayol et al, 1999;Landeta-Escamilla et al, 2016;Virginio et al, 2017). Nonetheless, the importance of this effect on the efficiency of the SIT is not clear, since there is no relationship between copulation duration and the ability of males to transfer sperm (Allinghi et al, 2007;Collins et al, 2012;Harmer, Radhakrishnan, & Taylor, 2006).…”

Genetic stability, genetic variation, and fitness performance of the genetic sexing Salaya1 strain for Bactrocera dorsalis, under long-term mass rearing conditions

“…A much higher value of RSI (0.80 ± 0.11) demonstrated that the Salaya1 sterile males can succeed more often in the mating competition with the wild females when they were irradiated at 50 Gy. This RSI value is unusally high when compared with the values from GSSs Vienna 8 (0.22 to 0.34) [ 38 , 39 ] and Tapachula-7 (0.4) [ 40 ]. However, this is consistent with a previous finding.…”

The Sterile Insect Technique (SIT) – an introduction

“…Virginio et al. () compared the mating performances of an established medfly strain with a new, transgenic strain in field cage experiments. No differences between the two SIT strains were found, although wild males consistently outperformed males of both SIT strains.…”

“…Augustinos et al (2017) compared two medfly genetic sexing strains in laboratory experiments, and report differences in egg hatch, pupation, and emergence rates, and in male tolerance to elevated temperatures. Virginio et al (2017) compared the mating performances of an established medfly strain with a new, transgenic strain in field cage experiments. No differences between the two SIT strains were found, although wild males consistently outperformed males of both SIT strains.…”