Padronização de uma técnica de análise de imagens da bomba cibarial de Rhodnius prolixus (hemiptera: triatominae) com vistas a avaliação do desempenho alimentar do triatomíneo frente a diferentes dietas

Abstract

Triatomines are of medical importance as they are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. They are temporary ectoparasites whose contact with their hosts is restricted to the time of blood meal, their only source of nutrients. Furthermore, it is during blood feeding that the parasites circulate between them and vertebrate hosts. In triatomines, hematophagy is of the solenophagic type. During feeding, most of the time is dedicated to the suction of blood by the insect, a process carried out by the pharyngeal (FP) and cibarial (CP) pumps. In the present study, we developed a methodology for processing images obtained in intravital microscopy experiments of the CP in the head of R. prolixus. We recorded on video during the feeding in vitro (diets with different viscosities) and in vivo (skin of mouse). Initially, 5th instar nymphs received two artificial diets with different viscosities (Locke: 0.78 mPa and Dextran: 6.9 mPa, determined at 60 rpm) containing ATP (phagostimulant) and Evans Blue (to facilitate visualization). From the curve of color variation in the regions of CP and the FP in the head, it was possible to monitor the activity of pumping liquids during insect feeding. Changing the viscosity of the artificial diet (from 0.78 to 6.9 mPa) had a negative role on insect ingestion rate, decreasing the frequency of the CP and the size of their blood meal. A calculation sheet was created to identify the peaks and valleys of the color variation curve presented by BC activity, allowing the calculation of the filling time (T. Enc) and emptying (T. Esv) of each activity cycle of CP of insects. From these times, it was possible to introduce in our analysis other parameters related to CP activity (e.g., period, filling and emptying speeds, etc.). When comparing the pumping performance of insects fed in vitro (Locke or dextran) in the three stretches evaluated (beginning, middle, and end), differences were only observed between the parameters (frequency (f), T.Ench, and T. Esv ) middle of feeding. The performance increase during feeding presented by insects fed with Locke and in vivo presented a distinct profile. While, in the former group, it was more lasting and symmetric considering the feeding time, the bugs that feed in the host, the profile was asymmetric with a clear tendency to decrease the pumping performance from the second half of the feed. The explanation for this difference would be associated with the physiological response of the host at the feeding site. The pattern of fluid displacement in the different regions of the CP chamber suggests that blood ingestion in R. prolixus is aided by the peristaltic movement of the pump's elastic wall.