Receptivity and Remating Propensity in Female Spodoptera litura (Fabricius) after Mating with an Irradiated Male or Its F(1) Male Progeny

SIMPLE SUMMARY: Spodoptera litura (Fabr.), an important pest of agricultural crops in India, can be controlled using the ‘Inherited or F(1) sterility technique’. The multiple mating tendency in female moths, their receptivity to remating after initial mating with radio-sterilized males and the sperm use pattern in sequential matings might influence the level of sterility induced in a radiation-mediated F(1) sterility program. In this study, the effect of irradiation was assessed on the quality of the ejaculate of exposed male moths, with a substantial decrease in insemination quality in their F(1) male progeny. Females mated to F(1) males showed an increased calling efficiency and remating propensity (with normal males) and influenced reproductive performance with a prolonged post (initial)-mating interval compared with the control moths. These findings on factors influencing female receptivity during remating and eventual reproductive sterilization might help optimize the technique. ABSTRACT: The ‘Inherited or F(1) sterility technique’ (IS), using sub-sterilized male moths, is a widely proposed pest management tool for Lepidoptera pests in general, and the tobacco cutworm Spodoptera litura (Fabr.) in particular. However, the multiple mating tendency of female moths and the ejaculate quality of male moths might influence the efficiency of this technique. Reduced ejaculate quality was observed in irradiated males, as evidenced by radiation’s impact on certain bio-parameters, such as the weight of the spermatophores and their protein content, sperm count, the molecular expression of the sex peptide receptor (SPR) and egg fertility, with a greater impact in F(1) male progeny. During the remating of females with untreated males, irrespective of the irradiation status of the first male, there was an increase in calling behavior, remating propensity and fertility in females, with a larger time gap between consecutive matings. The ability of F(1) male progeny to check remating propensity in females 24 h after the initial mating was lower than that of unirradiated males. Partially sterile (130 Gy) males were as successful as unirradiated males in inducing the level of mating refractoriness in females. Decreased ejaculate quality in F(1) male progeny could be associated with increased female receptivity during remating. Understanding the influence of male moth irradiation, insemination quality and post (initial)-mating intervals on the remating behavior of normal female moths and induced sterility might help in simulation modeling and optimizing IS insect programs.