Abstract
Simple SummaryThe Mexican fruit fly is an important pest of certain fruits. As part of its control, the Sterile Insect Technique (SIT) is used. This is an environmentally friendly means of control where insects are mass-reared, sterilized, and then released into areas where the pest is found. Sterile insects are dyed with a fluorescent pigment before release, to distinguish them from the wild population. The efficiency of this technique can be diminished if wild females first mate with a sterile male and then with a wild male. For the Mexican fruit fly, several transgenic strains have been developed that express a fluorescent protein marker for field detection, and are also used as reporters in the creation of strains with complex genetic systems. Here, we report on the biological attributes, mating competitiveness, and the proportion of paternity gained by the second male in twice-mated females with males from two transgenic strains. We found that the males expressing green florescence (443-G) had a better overall performance than the males expressing red fluorescence (419-R). We also found that females produced progeny mostly from the second male to mate with her. This could affect release ratios and diminish the efficiency of the SIT if wild females mate first with a sterile male but remate with a wild male, as she will then lay fertile eggs. These findings are helpful towards delimiting which strains can be used in the future, and determining the proportion of sterile to wild individuals that need to be released in affected areas, for the more efficient control of the Mexican fruit fly.Anastrepha ludens (Diptera: Tephritidae), is a damaging agricultural pest. Currently, the Sterile Insect Technique (SIT) is used as part of its control. The SIT consists of the mass-rearing, sterilization, and release of insects in target areas. Sterile males mate with wild females, and prevent them from laying fertile eggs. However, even if females mate with sterile males, they can then remate with a second male. If this second male is wild, then this could reduce the efficiency of the SIT by producing viable offspring. The amount of progeny produced by second males (P2 values) for A. ludens is unknown. Here, we evaluated the biological attributes, mating competitiveness, and the proportion of male paternity gained by the second male, using strains that carry fluorescent marker genes and can be potentially used to develop transgenic sexing strains. Furthermore, the transgenic strains were irradiated, to test their ability to induce sterility in females. We found that the 443-G strain had significantly higher larval survival than the 419-R strain. No significant difference was found between the two strains in their mating probability with wild females. We found P2 values between 67 and 74% for the 419-R and the 443-G strain, respectively. Second male sperm precedence only decreased slightly after 12 days, suggesting that sperm from the first and second male is not mixing with time, but rather the second male’s sperm prevails. Furthermore, sterile 443-G males induced significantly higher sterility in females than sterile males from the 419-R strain. The apparent lower ability of the 443-G strain to inhibit female remating should be further investigated. Knowledge of the pre and postcopulatory performance of transgenic strains will help in understanding their potential for control.
Highlights
The troubling reduction in insect diversity worldwide has made it imperative to focus efforts on environmentally friendly means of pest control
Post hoc tests revealed no significant differences between the two transgenic strains (Table 1)
Technique an environmentally friendly means of control. Ever, certain procedures, such as the marking of sterile males with a fluorescent certain procedures, such as the marking of sterile males with a fluorescent pigment, can pigmen can have negative on consequences the quality of pupae, antoincreased risk to huma have negative consequences the quality on of pupae, an increased risk human health health from the use pigments, andthat the some possibility some sterile adults will not b from the use of pigments, andofthe possibility sterilethat adults will not be dyed dyed properly
Summary
The troubling reduction in insect diversity worldwide has made it imperative to focus efforts on environmentally friendly means of pest control. The areawide management of tephritid flies through the Sterile Insect Technique (SIT) provides an opportunity to control pest insects such as the Mexican fruit fly, Anastrepha ludens [1,2]. The SIT is an autocidal control where insects are mass-reared, sterilized, usually through gamma radiation, and released in affected areas, where irradiated males will mate with wild females [3,4]. Sterile males transfer sperm with dominant lethal mutations, such that wild females will not be fertile [5]. If females are polyandrous, release ratios will have to be adjusted to take into account multiple mating with fertile wild males after a sterile mating. It is first important to determine the sperm precedence pattern for this species
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