Ultrastructure and transovarial transmission of endosymbiotic microorganisms in Palaeococcus fuscipennis (Burmeister) (Insecta, Hemiptera, Coccinea: Monophlebidae).

Ovaries ofPalaeococcus fuscipennis (Burmeister) are accompanied by large organs termed bacteriomes which are composed of large cells termed bacteriocytes. Each bacteriocyte is surrounded with small epithelial cells. The bacteriocyte cytoplasm is tightly packed with pleomorphic bacteria, whereas in epithelial cells small coccoid microorganisms are present. The number of coccoid bacteria is significantly lower than pleomorphic bacteria. The ovarioles containing choriogenic oocytes are invaded both by pleomorphic as well by coccoid bacteria. Microorganisms traverse the follicular epithelium and enter the perivitelline space. During advanced choriogenesis, endosymbionts are accumulated in the deep depression of the oocyte. Bacteria do not enter the ooplasm until the end of oocyte growth.