The effect of age on the mating competitiveness of male Glossina fuscipes fuscipes and G. palpalis palpalis

Abstract

The effect of age on male Glossina fuscipes fuscipes, Newstead, and Glossina palpalis palpalis, Austin (Diptera: Glossinidae) competiveness were investigated with a view to estimate optimal age for sterile male release. Sterile insect technique involves the mass production, sterilization and sequential release of males of the target species to out compete the wild male population. Mating between released sterile males and wild females produce inviable progeny and the population is reduced over several generations to unsustainable levels. It is vital that the released male are of high quality and are sexually competitive. Age is one parameter affecting the sexual competiveness of the male tsetse fly. The optimal release age was estimated by assessing sexual competitiveness of flies of different age categories, 1, 5, 8 and 13-days after adult eclosion. A walk-in field-cage was used in order to approximate as closely as possible the actual field scenario during sterile insect release programes. It was shown that 8 and 13-day old males mated significantly more frequently, i.e. were more competitive, in the presence of equal numbers of 1 and 5-day old males. The age of male tsetse flies significantly affected competitiveness in both species studied. The ability of G. f. fuscipes to inseminate was not age dependent, and insemination occurred in all females that mated regardless of male age. In G. p. palpalis, however, 1-day old males were least able to inseminate. Mating duration was not significantly affected by age in both species. Eight to thirteen day old males of the test species are here recommended as the optimal sterile male release age.RésuméL'effet de l'âge sur la compétitivité des mâles de Glossina fuscipes fuscipes et de Glossina palpalis palpalis a été étudié en vue de déterminer l'âge optimal pour le lâcher de mâles stériles. La technique de l'insecte stérile (TIS) consiste en une production de masse, en la stérilisation et au lâchage de mâles de l'espèce cible afin qu'ils competissent avec la population de mâles sauvages. L'accouplement entre mâles stériles lâches et femelles sauvages ne produit pas de progéniture, ce qui conduit au bout de plusieurs générations à une réduction de la population à un niveau non sur vivable. Il est primordial que les mâles lâches soient de bonne qualité et sexuellement compétitifs. L'âge est l'un des paramètres affectant la compétitivité des mouches tsetse mâles. Il était donc nécessaire d'estimer l'âge optimal pour lâcher des mâles en comparant la compétitivité de différentes catégories d́âges (1, 5, 8 et 13 jours après leur émergence). La méthode dite du « field-cage » a été utilisée afin d'étudier le comportement des mâles TIS dans les conditions aussi proches que possible de la réalité. Il a été démontré que les mâles de 8 et 13 jours s'accouplent plus fréquemment que les mâles de 1 a 5 jours. Pour les deux espèces étudiées, l'âge affecte significativement la compétitivité des tsetse mâles. La capacité des mâles de G. f. fuscipes à inséminer n'est pas fonction de l'âge ...

Mating performance of Glossina palpalis gambiensis strains from Burkina Faso, Mali, and Senegal

“…The behaviour of females that were not ready to mate was similar to that described for Glossina austeni Newstead and G. m. morsitans (Huyton & Langley, 1982), and G. pallidipes (Mutika et al, 2001). These types of field cage study have likewise been used to assess the effect of various abiotic or biotic parameters on the mating behaviour and competitiveness of tsetse flies, e.g., the effect of age on G. f. fuscipes and G. p. palpalis (Abila et al, 2003), of low temperatures on G. pallidipes (Mutika et al, 2002), and of low temperatures in combination with irradiation on G. p. gambiensis ( GN Mutika, unpubl. ).…”

“…The flight activity that was noted in both field cage setups was similar in that there was infrequent movement from resting positions and that the flies spent most of their time grooming themselves as noted for Glossina pallidipes Austen (Mutika et al, 2001). These types of field cage study have likewise been used to assess the effect of various abiotic or biotic parameters on the mating behaviour and competitiveness of tsetse flies, e.g., the effect of age on G. f. fuscipes and G. p. palpalis (Abila et al, 2003), of low temperatures on G. pallidipes (Mutika et al, 2002), and of low temperatures in combination with irradiation on G. p. gambiensis ( GN Mutika, unpubl. There seems to be a complex mix of environmental conditions that are necessary for mating activity to take place and this may include temperature and light intensity above a certain threshold, and adequate humidity (Okiwelu, 1982).…”

“…Direct observation of tsetse mating behaviour in field cages has been done previously under controlled conditions (Mutika et al, 2001;Abila et al, 2003) but the open field conditions used at CIRDES were a first attempt to observe mating behaviour in outdoor field cages. These studies are important as they provide an opportunity to assess the mating behaviour and performance of reared and wild insects under controlled conditions.…”

“…These studies are important as they provide an opportunity to assess the mating behaviour and performance of reared and wild insects under controlled conditions. Direct observation of tsetse mating behaviour in field cages has been done previously under controlled conditions (Mutika et al, 2001;Abila et al, 2003) but the open field conditions used at CIRDES were a first attempt to observe mating behaviour in outdoor field cages. Dean et al (1969) used a similar approach but they worked with bigger cages, 26.7 and 752.5 m 2 , in which competitiveness and compatibility were assessed indirectly by making inferences from production of larvae.…”

Life table assay of field‐caught Mediterranean fruit flies, Ceratitis capitata, reveals age bias

“…Evidence suggests that the sexual competitiveness of male C. capitata (N Papadopoulos, unpubl.) and other species targeted with this method (e.g., Abila et al, 2003) is significantly influenced by age. An adequate understanding of this influence could lead to increased efficiency of the method.…”