Development of Trypanosoma cruzi after starvation and feeding of the vector - a review.

Trypanosoma cruzi develops in the intestinal tract of reduviid bugs and may be affected by changes in the nutritional state of the vector. In regularly fed Triatoma infestans the population of T. cruzi in the rectum consists mainly of equal amounts of epi- and trypomastigotes. Starvation of the bug reduces the total number of flagellates and the number and percentage of trypomastigotes. The number and the percentage of drop-like forms and of resulting spheromastigotes, however, increases up to 30% 60 days after the last feeding (daf). Feeding of starved bugs (60 daf) reduces the original population density, which then increases again. In starved bugs 1 daf spheromastigotes (including intermediate forms) have almost disappeared and epimastigotes dominate. In addition "giant cells" (a multiple division stage) comprise about 10% of the population and in the following two days this form represents on average 30-50% of the total population, before disappearing nearly completely. Feeding the vector at 40 daf; a) induces the appearance of pure populations of trypomastigotes in immediately deposited drops of bug urine; b) induces metacyclogenesis in epimastigotes, and c) reduces metacyclogenesis in spheromastigotes. Incubating isolated recta together with the Malpighian tubules in Drosophila Ringer's solution and initiating the excretion with 5-hydroxy-tryptamine also induces metacylogenesis in epimastigotes.