Mating competitiveness of sterile male Anopheles coluzzii in large cages.

Jeremie Rl Gilles,Simon P Sawadogo,Abdoulaye Niang,Georges A Ouédraogo,Roch K Dabiré,Abdoulaye Diabaté,Fréderic Tripet,Omnia Fatherhaman,David Damiens,Rosemary S Lees,Hamidou Maïga,Olivier Roux

doi:10.1186/1475-2875-13-460

Abstract

BackgroundUnderstanding the factors that account for male mating competitiveness is critical to the development of the sterile insect technique (SIT). Here, the effects of partial sterilization with 90 Gy of radiation on sexual competitiveness of Anopheles coluzzii allowed to mate in different ratios of sterile to untreated males have been assessed. Moreover, competitiveness was compared between males allowed one versus two days of contact with females.MethodsSterile and untreated males four to six days of age were released in large cages (~1.75 sq m) with females of similar age at the following ratios of sterile males: untreated males: untreated virgin females: 100:100:100, 300:100:100, 500:100:100 (three replicates of each) and left for two days. Competitiveness was determined by assessing the egg hatch rate and the insemination rate, determined by dissecting recaptured females. An additional experiment was conducted with a ratio of 500:100:100 and a mating period of either one or two days. Two controls of 0:100:100 (untreated control) and 100:0:100 (sterile control) were used in each experiment.ResultsWhen males and females consort for two days with different ratios, a significant difference in insemination rate was observed between ratio treatments. The competitiveness index (C) of sterile males compared to controls was 0.53. The number of days of exposure to mates significantly increased the insemination rate, as did the increased number of males present in the untreated: sterile male ratio treatments, but the number of days of exposure did not have any effect on the hatch rate.DiscussionThe comparability of the hatch rates between experiments suggest that An. coluzzii mating competitiveness experiments in large cages could be run for one instead of two days, shortening the required length of the experiment. Sterilized males were half as competitive as untreated males, but an effective release ratio of at least five sterile for one untreated male has the potential to impact the fertility of a wild female population. However, further trials in field conditions with wild males and females should be undertaken to estimate the ratio of sterile males to wild males required to produce an effect on wild populations.

Highlights

Understanding the factors that account for male mating competitiveness is critical to the development of the sterile insect technique (SIT)
Competitiveness of irradiated Anopheles coluzzii males When males and females consorted for two days, a significant difference in insemination rate was observed with different ratios of sterile to untreated males (LRT χ2 = 35.86; df = 4; P < 0.001) (Table 1)
Irradiation for sterilization had an impact on the ability of An. coluzzii males to compete for mates in a large cage setting

Summary

Introduction

Understanding the factors that account for male mating competitiveness is critical to the development of the sterile insect technique (SIT). A renewed interest in the development of environmentfriendly vector control strategies using sterile insects raises hopes of being able to reduce the high reproductive rate of mosquitoes. The sterile insect technique (SIT) is based on inundative and repeated releases of sterile insects to induce sterility in the wild population and suppress the target pest species [8]. In El Salvador, experimental releases of chemosterilized male Anopheles albimanus drastically reduced the wild mosquito population in a pilot area [12]. Several trials conducted in the 1970s produced limited success due to the poor competitiveness of released males for wild females (reviewed in [13]). Sterile male Anopheles quadrimaculatus were unable to control a caged field population [14]

Methods

Results

Conclusion