Natural Trypanosoma cruzi Infection and Climatic Season Influence the Developmental Capacity in Field-Caught Mepraia spinolai Nymphs.

Simple Summary: Triatomines are hemimetabolous and hematophagous insect vectors of Trypanosoma cruzi, the parasite that causes Chagas disease. The life cycle of triatomines is composed of five nymphal stages and an adult stage. The wild kissing bug Mepraia spinolai is distributed in a vast area of the semiarid Mediterranean ecosystem of South America, characterized by strongly marked seasons. The population structure of this vector changes during the different seasons, suggesting its development is controlled under natural conditions. In this study, we performed a biological assay to study this vector development after two laboratory feedings. We collected nymphs, first to fourth instars, in eight M. spinolai populations during the transition of late fall to winter (cooling period) and spring (warming period) of three consecutive years. The gathered information with vectors molting twice suggests that development is differentially controlled in nymphs from first and fourth instars depending on the climatic period of collection. Additionally, T. cruzi infection changes development forward only in nymphs of second and fourth instars of the warming period. Our findings suggest that the effect of the climatic period and T. cruzi infection on the development of this vector species is a stage-dependent phenomenon. In this study, we evaluated the effect of the climatic season and infection by Trypanosoma cruzi, etiological agent of Chagas disease, on the molting capacity of the triatomine vector Mepraia spinolai endemic to Chile. We used wild-caught first-to-fourth instar nymphs during cooling (fall and winter) and warming (spring) periods. After capturing, nymphs were fed at the laboratory, and maintained under optimal rearing conditions. Feeding was repeated 40 days later. We followed-up the molting events on 709 nymphs, recording one, two or the absence of molts after two feeding opportunities. Within the same climatic period, only infected second- and fourth-instar nymphs from the warming period showed a larger proportion of double molting compared to uninfected nymphs. Regarding the climatic period, infected and uninfected first- and fourth-instar nymphs exhibited a larger proportion of double molting in the warming and cooling periods, respectively. The pattern of non-molting nymph occurrence suggests they probably reach diapause by environmental stochasticity. The effect of the climatic period and T. cruzi infection on the development of M. spinolai is an instar-dependent phenomenon, highlighting the occurrence of finely synchronized processes at different moments of the life cycle of such an hemimetabolous insect as triatomines. [ABSTRACT FROM AUTHOR]