Histochemical demonstration of oxidoreductase activities in the fat body and symbionts of Blattella germanica (Blattodea) following chlortetracycline-treatment

The metabolic apport of prokaryotic symbionts in the fat body of Blattella germanica was investigated by histoenzymatic methods, using chlortetracycline-treated and normal strains. In the experimental insects, bacteriocytes showed a decreased oxidoreductase activity, whereas the staining intensity of the other cell types was generally unchanged. Electron microscopic observations showed that some bacteria were still present in the bacteriocytes of the treated insects, but exhibited degeneration patterns to a different extent; therefore, they are not likely to carry on any enzymatic activity. Hence, chlortetracycline, an antibiotic that blocks the transovaric transmission of the symbionts, is active also on the endocellular symbionts of the fat body.