Morphology, histochemistry, and ultrastructure of mycetome and its rickettsial symbiotes in Cimex lectularius L.

The haematophagous bug, Cimex lectularius L., harbored in mycetomes two kinds of rickettsia-like microorganisms: morphologically, one was a small rod, the other pleomorphic, often globular. Both kinds of symbiotes had Gram-negative profiles and nuclear areas. 'Rod-shaped' symbiotes were enveloped by amorphous materials but lay freely in the mycetomes. The 'pleomorphic' symbiotes were enclosed by vacuolar membranes. Both symbiotes were lysed in cytolysomes and became masses of membranes, suggesting that this is a method of maintaining a population balance between host and symbiote.