Histological observations on transovarial transmission of a yeast-like symbiote in Nilaparvata lugens Stal (Homoptera, Delphacidae)

Transovarial transmission of a yeast-like symbiote (YLS) in the brown planthopper, Nilaparvata lugens Stal, was observed with light and electron microscopy. Light micrographs showed that there was no YLS in testes and spermathecae of the mated females, indicating that sperm is not involved in the transovarial transmission of the symbiote. Both light and electron micrographs showed the processes of YLS transmission from fat body to the oocyte. In females, the symbiotes in mycetocytes moved out of the syncytium, which is formed from a layer of fat body cells, by exocytosis, and released into hemocoel. Then, the free YLS in hemolymph approached to the ovarioles near pedicel and were enclosed by follicle cells. They entered the follicle cells around the primary oocyte by endocytosis at epithelial plug of the ovariole. The YLS aggregated at the posterior end of the mature egg after entering, and finally formed a symbiote ball.