Ultrastructure and transovarial transmission of endosymbiotic microorganisms in Conomelus anceps and Metcalfa pruinosa (Insecta, Hemiptera, Fulgoromorpha)

Endosymbiotic microorganisms commonly occur in fulgoromorphans, as in other plant sap-sucking hemipterans. Large syncytial organs termed mycetomes are present in the body cavities of Conomelus anceps (Delphacidae) and Metcalfa pruinosa (Flatidae), in the close vicinity of the ovaries. The mycetomes are surrounded by a one-layered epithelium. The mycetome cytoplasm is filled with yeast-like symbiotic microorganisms (YLSs). The YLSs are transovarially transmitted to the next generation. The endosymbionts are released from the mycetomes and migrate towards the ovarioles containing vitellogenic oocytes. The YLSs pass through the cells of the ovariole stalk (pedicel) and enter the perivitelline space. Then, a deep depression is formed at the posterior pole of the oocyte. The YLSs accumulate in the oocyte depression and form a characteristic "symbiont ball". The mycetome cytoplasm of Metcalfa pruinosa as well as epithelial cells surrounding the mycetome contain small, rod-shaped bacteria.