Transfer of inoculum of Metarhizium anisopliae between adult Glossina morsitans morsitans and effects of fungal infection on blood feeding and mating behaviors

Abstract

The transfer of conidia of Metarhizium anisopliae between tsetse flies Glossina morsitans and the effects of fungal inoculation on mating and blood meal feeding behaviors were investigated in the laboratory. Male or female flies were inoculated with fungal conidia ("donors") and allowed to pair with fungus-free mate of opposite sex ("recipients") at 1-day-interval up to three mates. Fungus-treated male or female "donor" flies as well as their mates "recipients" died from fungal infection. However, mortality in male "recipient" flies declined with successive mating, from 82.5 to 32.5 %. Fungus-treated males readily located female flies and mating was successful in most cases comparable to the controls. There were no significant differences (P > 0.05) in mean duration of mating, number of jerking movements between fungus-treated and fungus-free males for all the mating lines, except in the number of jerking movements when male flies mated with the 3rd line female flies. Fungus-treated and fungus-free female flies previously mated with treated and non-treated males showed refractoriness during subsequent pairings. The number of fertile female flies was higher (P < 0.05) in fungus-free than in fungus-treated treatments, thus producing more pupae. High concentration of fungus (3.0 × 10⁶ conidia ml^-1) significantly (P < 0.05) reduced blood meal intake of flies. This study has shown that fungal infection does not affect the mating behavior of tsetse flies and fly-to-fly contamination does occur during matings. These are important attributes if entomopathogenic fungi have to be used in auto-dissemination strategy and be integrated into sterile insect technique.

Keywords: Blood meal; Entomopathogenic fungus; Glossina morsitans morsitans; Infection; Mating behavior; Metarhizium anisopliae; Reproduction; Transfer of inoculum; Tsetse.

Fig. 1

Mean duration of copulation (min) of fungus-free male “recipient” Glossina morsitans morsitans mated with Metarhizium anisopliae-treated and fungus-free female “donors”. Four replicates of 10 flies each. Each “donor” fly was allowed to mate three times with different mates at 1-day-interval. Bars denote means ± one standard error (P = 0.05, t test)

Fig. 2

Mean duration of copulation (min) of Metarhizium anisopliae-treated and fungus-free male “donor” Glossina morsitans morsitans mated with fungus-free female “recipients”. Four replicates of 10 flies each. Each “donor” fly was allowed to mate three times with different mates at 1-day-interval. Bars denote means ± one standard error (P = 0.05, t test)

Fig. 3

Mean number of jerking movements of fungus-free male “recipient” Glossina morsitans morsitans mated with Metarhizium anisopliae-treated and fungus-free female “donors”. Four replicates of 10 flies each. Each “donor” fly was allowed to mate three times with different mates at 1-day-interval. Bars denote means ± one standard error (P = 0.05, t test)

Fig. 4

Mean number of jerking movements of fungus-free female “recipient” Glossina morsitans morsitans mated with Metarhizium anisopliae-treated and fungus-free male “donors”. Four replicates of 10 flies each. Each “donor” fly was allowed to mate three times with different mates at 1-day-interval. Bars denote means ± one standard error (P = 0.05, t test)