Extracellular and intracellular rickettsia-like microorganisms in gonads of mosquitoes.

The mosquitoes Culex tigripes, C. decens and C. quinquefasciatus have been investigated by electron microscopy. An intracytoplasmic rickettsia-like microorganism is present in ovaries and testes of the three species. An extracellular form of a rickettsia-like microorganism is described in the testis of C. tigripes in which it sometimes appears in great number. The extra- and intracellular forms present ultrastructural differences. The possibility they represent two different morphotypes of the same microorganism or simply two different types is discussed. They both disappear after treatment with tetracycline. This is believed to be the first electron microscope description of extracellular rickettsia-like cells in mosquitoes.