Abstract: Wolbachia and Cardinium, with the ability to induce cytoplasmic incompatibility (CI), are maternally inherited intracellular bacteria known to manipulate the reproduction of their hosts. The exact mechanisms of CI which is induced by these two endosymbionts in the same host are unknown. This study tried to investigate the reproductive manipulation of Wolbachia or/and Cardinium infected spider mite Tetranychus piercei McGregor by crossing experiment and fluorescence in situ hybridization (FISH). The results indicated that Wolbachia-infected males induced weak CI. In Guangzhou population of the spider mite, approximate 17.8%±1.6% of all eggs did not hatch in the incompatible cross U/Iw. Cardinium-infected and Wolbachia and Cardinium doubly infected males caused severe CI. The unhatched eggs in the incompatible cross U/Ic and U/Iwc accounted for 70.3%±1.3% and 72.9%±1.2%, respectively, the number of eggs laid per doubly infected female was 35.2±1.2, significantly higher than that of singly (Wolbachia or Cardinium) infected female. There is a positive correlation between CI levels and infection status of the developing sperm. Wolbachia and Cardinium mainly enter the oocytes with trophic flow from nurse cells, midgut and oviduct. The results might provide foundation for understanding the maternally inherited mechanisms of Wolbachia and Cardinium.

Key words: Tetranychus piercei , Wolbachia, Cardinium, cytoplasmic incompatibility, fluorescence in situ hybridization (FISH)