Effects of Sublethal Concentrations of Tetracycline Hydrochloride on the Biological Characteristics and Wolbachia Titer in Parthenogenesis Trichogramma pretiosum

SIMPLE SUMMARY: Trichogramma pretiosum is an important natural enemy of lepidopteran pests. Wolbachia is an intracellular endosymbiont that induces parthenogenesis in the parasitoid T. pretiosum. Tetracycline antibiotics are widely used to remove endosymbiont Wolbachia from insect hosts. However, the sublethal effects of tetracycline on the development of T. pretiosum and the population dynamic of Wolbachia in T. pretiosum are still unclear. In our present study, after treatment with sublethal concentrations of tetracycline over ten generations, the biological parameters (longevity, parasitized eggs, and fecundity) of treated females and the percentage of female offspring were significantly lower than those in the control. Moreover, the Wolbachia titer in females sharply declined after two generations of antibiotic treatments and decreased to a lower level even after ten successive generations of antibiotic treatments. In addition, the control group with a higher Wolbachia titer produced more female offspring than the tetracycline treatment groups with a lower Wolbachia titer. These results provide new insights into the complex interaction between arthropods and Wolbachia to antibiotic stress. ABSTRACT: Trichogramma pretiosum Riley is an important natural enemy and biological control agent of lepidopteran pests. Wolbachia is an intracellular endosymbiont that induces parthenogenesis in the parasitoid T. pretiosum. In this paper, the sublethal effects of the antibiotic tetracycline hydrochloride on the development and reproduction of T. pretiosum were studied. Emerged females were fed with sublethal concentrations (LC(5), LC(15), and LC(35)) of tetracycline for ten generations. The biological parameters (longevity, parasitized eggs, and fecundity) of treated females significantly reduced compared with the control Moreover, the percentage of female offspring in the treatments significantly reduced, but the percentage of male offspring significantly increased. In addition, the Wolbachia titer sharply reduced after two generations of antibiotic treatments, but it could still be detected even after ten successive generations of antibiotic treatments, which indicated that Wolbachia was not completely removed by sublethal concentrations of tetracycline. The control lines with higher Wolbachia titers produced more female offspring than the tetracycline treatments with lower Wolbachia titers, indicating that the Wolbachia titer affected the sex determination of T. pretiosum. Our results show that sublethal concentrations of tetracycline had adverse effects on the development of T. pretiosum, and Wolbachia titers affected the sexual development of T. pretiosum eggs.