title: Mating competitiveness of sterile male Anopheles coluzzii in large cages.
abstract: BACKGROUND
  Understanding 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.
  
  
  METHODS
  Sterile 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.
  
  
  RESULTS
  When 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Institut de Recherche en Sciences de la Santé/Centre Muraz, BP 545 Bobo-Dioulasso, Burkina Faso. maigahamid@yahoo.fr.
authors.forename: Hamidou
authors.initials: H
authors.lastname: Maïga
authors.forename: David
authors.initials: D
authors.lastname: Damiens
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Niang
authors.forename: Simon P
authors.initials: SP
authors.lastname: Sawadogo
authors.forename: Omnia
authors.initials: O
authors.lastname: Fatherhaman
authors.forename: Rosemary S
authors.initials: RS
authors.lastname: Lees
authors.forename: Olivier
authors.initials: O
authors.lastname: Roux
authors.forename: Roch K
authors.initials: RK
authors.lastname: Dabiré
authors.forename: Georges A
authors.initials: GA
authors.lastname: Ouédraogo
authors.forename: Fréderic
authors.initials: F
authors.lastname: Tripet
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Diabaté
authors.forename: Jeremie R L
authors.initials: JR
authors.lastname: Gilles
mesh_terms: D000818:Animals; D000852:Anopheles / Q000502:physiology* / Q000528:radiation effects*; D003163:Competitive Behavior / Q000528:radiation effects; D005260:Female; D005720:Gamma Rays; D008297:Male; D012726:Sexual Behavior, Animal / Q000528:radiation effects*