The effects of aposymbiosis and of an infection with Blastocrithidia triatomae (Trypanosomatidae) on the tracheal system of the reduviid bugs Rhodnius prolixus and Triatoma infestans.

We have investigated the effects of the absence of symbionts and of infection with a trypanosome on the tracheal supply to different organs in larvae of the blood-sucking bugs, Rhodnius prolixus and Triatoma infestans. In bugs grown without symbionts there were extensive reductions in the tracheal supply to all the internal organs examined. These bugs also excreted less fluid after blood meals, perhaps because of a reduction in the oxygen supply to the Malpighian tubules. Inclusion of vitamin B in the diet of these affected insects reversed both the adverse effects on diuresis and on the extent of the respiratory supply to the different internal organs. The results of these studies suggest that vitamin B may play a key role in the development and maintenance of an adequate tracheal supply to the tissues in these insects. Infection with the trypanosome Blastocrithidia triatomae also greatly reduced the density of tracheoles supplying the rectum, small intestine and Malpighian tubules in infected T. infestans, but not in R. prolixus. It is possible, therefore, that the parasite exerts at least part of its pathogenic effect by causing a vitamin B deficiency, that in turn affects oxygen supply to the tissues.