Abstract
The control of Aedes albopictus through Sterile Male Releases requires that the most competitive males be mass-reared and sterilized usually with gamma- or X-ray radiation prior to release. Developing an understanding of the impact of irradiation treatment on flight performance in sterile males is very important because any fitness cost may reduce the efficacy of SIT intervention in the field. Here, we examined the role of irradiation exposure and sugar-feeding on daily flight activity and performance of Ae. albopictus males sterilized during pupal stage with gamma-radiation at 35Gray from a Caesium 137 source. We used a previously developed automated video tracking system to monitor the flight activity of different groups of sterile and control non-sterile males over 24 hours in a flight arena. This monitoring took place under controlled laboratory conditions and we wished to quantify the daily flight activity and to highlight any changes due to radiation treatment and nutritional conditions (starved versus sugar fed). Our experimental evidence demonstrated a characteristic diurnal flight activity with a bimodal pattern regardless of the treatment. Precisely, both irradiated and non-irradiated males exhibited two distinct peaks in flight activity in the morning (6–8 a.m.) and late afternoon (4–6 p.m.). Under changing physiological conditions, irradiated males were generally more active over time and flew longer overall distances than control male populations. These results suggest some internal circadian control of the phase relation to the light-dark cycle, with evidence for modification of flight performance by nutritional status. The fact that daily activity patterns are alike in irradiated and control Ae. albopictus males, and that sterile males could display higher flight performance, is in contrast with the hypothesis that irradiation treatment appears to reduce the fitness of male mosquitoes. We discuss the implications of the present study in sterile-male release programs against Ae. albopictus.
Highlights
Aedes (Stegomyia) albopictus (Skuse, 1984) (Diptera: Culicidae) plays an important role as a vector of chikungunya, dengue, and other arboviruses, its vector role is often assumed to be less than that of its sibling, Aedes aegypti [1,2,3]
Measurements of the 24-hrs cycles of flight activity were generated from 8 videos independently recorded from different paired experiments using groups of sterile and normal Ae. albopictus males, either under fed or unfed conditions (n = 15–20 males mosquitoes in each of the 4 conditions x 2 replicates)
It has generally been established that ionizing radiation generates chromosomal aberrations and dominant lethal mutations in sperm [29], but somatic damage induced by irradiation may reduce the competitive fitness of sterile males, even in the case of low-level radiation such as that applied in the present study
Summary
Aedes (Stegomyia) albopictus (Skuse, 1984) (Diptera: Culicidae) plays an important role as a vector of chikungunya, dengue, and other arboviruses, its vector role is often assumed to be less than that of its sibling, Aedes aegypti [1,2,3]. The Sterile Insect Technique (SIT) is at the front line of such anti-vector campaigns, as it offers a highly selective means of controlling vector populations in synergy with concerns for human health and environmental safety [6, 7]. It is an autocidal method in which mass-reared, irradiated males are released in overwhelming numbers to compete for mates with wild insects [8, 9]. The effectiveness of area-wide implementation of SIT has been demonstrated previously in control of the tsetse fly; vector of Trypanosoma brucei, the causative agent of sleeping sickness in humans [10], and in several trials against devastating agricultural and livestock pests [11]
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