Direct and indirect pathways of fitness‐impact in a protozoan‐infected kissing bug

Abstract

Parasites can reduce host fitness through short‐term mortality, complete or partial castration, or slight reductions in host fecundity. Hosts may reduce reproductive effort as an adaptive strategy to tolerate parasitism. However, host fitness reduction may be unrelated to host adaptation but represent a pathological side‐effect of infection. The present study evaluates experimentally the direct and indirect impact of the protozoan parasite Trypanosoma cruzi on the investment of female kissing bugs in reproductive tissue. The presence of the parasite decreases gonad weight but this effect disappears when body size is included as covariate. To examine in more detail the set of causal relationships involved, a structural equation modelling analysis is performed using body size, moulting time and nutrition as predictor variables on gonad weight in the presence and absence of the protozoan. The results obtained indicate that, irrespective of the pathway and status of infection, female kissing bugs showing a slow development tend to have lighter gonads. On the other hand, the importance of blood ingestion for gonad weight is dependent on body size and contingent on the status of infection. Uninfected individuals tend to invest more in reproductive tissue when ingesting more blood during their ontogeny, and the opposite situation is observed for infected insects. These results indicate that gonad weight reduction in T.cruzi‐infected Mepraia spinolai (Porter, 1934) is a consequence of nutrition curtailment and body size reduction rather than an adaptive strategy to cope with infection.

Rhodnius prolixus Life History Outcomes Differ when Infected with Different Trypanosoma cruzi I Strains

“…[15][16][17][18][19][20] This idea is mainly based on studies of the triatomine species Triatoma infestans. 15,[21][22][23][24][25][26][27] Investigations into the effect of T. cruzi infection on other triatomine species have yielded variable results, with some results suggesting that T. cruzi reduces triatomine survival and or reproduction, [28][29][30][31][32] and others finding little to no effect. [33][34][35] Although some of the discrepancies may be due to differences in experimental conditions or design, it is also possible that the inherent variability of T. cruzi itself is a driver of the variable fitness outcomes in infected triatomines, as it is in its mammal hosts.…”

“…To the best of our knowledge, this has not been tested, as all published studies on the effect of T. cruzi on triatomines have been limited to one T. cruzi strain-I triatomine species system. 15,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Given that a principle focus in Chagas disease prevention is the interruption of T. cruzi transmission by triatomine bugs living in and around human homes, it is important to understand the full range of outcomes that trypanosome infection can have on triatomines. Therefore, we asked, does variability exist in the effect of different T. cruzi strains on its triatomine host?…”

Sex‐dependent infection causes nonadditive effects on kissing bug fecundity

“…Parasite‐induced changes in host body size may be the proximal factor involved in host fitness reduction. Previous studies have reported that the protozoan T. cruzi has a strong impact on several life history traits of M. spinolai (Botto‐Mahan, ; Botto‐Mahan, Cattan, & Medel, ; Botto‐Mahan et al., ). In this study, infected females reached smaller size at maturity compared to those uninfected, suggesting that like other parasite species, T. cruzi probably curtails essential nutrients involved in host growth (Hurd, ; Thompson, ).…”

“…For example, infected insects show longer developmental time and reduced body weight compared to uninfected insects (Botto‐Mahan, ). Likewise, gonads of infected females have 36.7% less weight than those of uninfected females (Botto‐Mahan, Ossa, & Medel, ). Here, we inquire into the importance of male and female infection costs on host reproduction using an experimental design that permits the assessment of additive (independent) and nonadditive (interactive) effects on host reproductive success.…”

Ontogenetic changes in wild chagasic bugs (Dipetalogaster maximus): exploring morphological adaptations in pre-adult and adult stages

“…Secondly, we compared how both sexes in the adult stage differ in their investment to traits related to the same functions indicated above, but we also included fecundity. Thus, for the fecundity function, we measured abdominal length as this is a proxy of fecundity in insects (Preziosi et al, 1996) and triatomines (Botto-Mahan et al, 2008). For comparative purposes, we also measured immature abdominal length.…”