γ Ray Dosimetry and Mating Capacity Studies in the Laboratory on Aedes albopictus Males

Abstract

In Italy, Aedes albopictus Skuse is currently recognized as the most dangerous mosquito, and as currently applied conventional control methods gave unsatisfactory results, we are developing alternative strategies such as the sterile insect technique. To find the optimal sterilizing dose, male pupae were exposed to different doses of gamma rays in the range 20-80 Gy, generated by a Cesium-137 source. The effects of male pupal age at irradiation and gamma ray dose on adult male emergence, sterility level, longevity, and mating capacity were evaluated, and dose-response curves of residual fertility were calculated. Radiation tests were also performed on female pupae to observe their reproductive capacity in case of accidental release. Results confirmed that the age at which the male pupa is irradiated is an important factor that affects the longevity of the adult, whereas the effect of age on the induced sterility level is less pronounced. When male pupae older than 30 h were irradiated, the longevity of the adults was not affected by doses up to 40 Gy. The 40-Gy dose appeared sufficient to induce high level of sterility (>99%) at any male pupal age for all the strains tested. The duration of coupling and the number of mated females per male appeared to be affected by the radiation received by male pupae only at doses higher than 40 Gy. The female pupae were more sensitive to radiation than male pupae, with strong reduction in fecundity and fertility at 20 Gy and complete suppression of oviposition at higher doses.

Cross-Mating Compatibility and Competitiveness among Aedes albopictus Strains from Distinct Geographic Origins - Implications for Future Application of SIT Programs in the South West Indian Ocean Islands

“…This radiation dose represents the best compromise between the expected level of sterility and mating competitiveness. Consistent with evidence from our previous laboratory and semi-field investigations [78, 24], the radiation dose (35 Gy) currently applied to sterilize Ae . albopictus males is expected to induce 95–97% sterility.…”

A bacterium against the tiger: preliminary evidence of fertility reduction after release of Aedes albopictus males with manipulated Wolbachia infection in an Italian urban area

“…albopictus eggs produced by ENEA was amplified by mass-rearing at ENEA Casaccia (Rome) and Centro Agricoltura Ambiente G. Nicoli (CAA, Crevalcore, Bologna) based on standard operating procedures developed at CAA. 33 The resulting eggs were then hatched at ENEA Casaccia following the protocol described in Balestrino et al 33 Larval rearing trays were set up starting with 2000 first-instar larvae (larval density of two larvae/mL deionized water) at 28 ∘ C, 80% relative humity (RH) and a 14:10 h light/dark photoperiod. Larvae were fed for 4 days with increasing doses (0.2, 0.4, 0.6 and 0.8 mg/larva/day) of a liquid diet consisting of 50% tuna meal, 36% bovine liver powder, 14% brewer's yeast and 0.2% w/v vitamin mix (IAEA-BY diet).…”

Sugar administration to newly emerged Aedes albopictus males increases their survival probability and mating performance

“…The newly emerged males must go through the holes to take flight. at 30 Gy at the Medical Physics Department of St. Anna Hospital (Ferrara, Italy), just before release (Balestrino et al, 2010).…”

“…Domestication may lead to abnormal behaviors in laboratory reared insects (Bartlett, 1984); indeed one study found that after just 9-16 weeks of colonization males Culex tarsalis were unable to compete for wild females (Reisen et al, 1982). The exposure to ionizing radiation commonly used to sterilize mosquitoes for use in the SIT causes somatic damage which may affect ability to perform well in the field (Helinski et al, 2009) though the dose and timing can be adjusted to minimize the negative effects (Balestrino et al, 2010). In the context of mosquito control strategies relying on the release of male adults which must disperse, find and successfully mate with wild females, such as the SIT, it is of crucial importance to formulate optimal larval diets in order to produce sterile males which are highly competitive with wild males.…”