Fig. 1:
potential processes involved in the density-dependent population regulation in triatomines. Blue stars identify those processes that were measured in the laboratory. The red arrows indicate the expected direction of the change in the response of each process (increasing ↑ or decreasing ↓) as a function of an increase in Rhodnius prolixus density, which was set-up by the experimenter in the laboratory design (see text for the densities used).
Fig. 2:
schematic drawing of the experimental set-up. The central box (box 1) is where the kissing bugs and the hamster were located to carry out the density-dependent experiments, and the three lateral boxes (boxes 2, 3 and 4) had one un-accessible hamster each, and were used to evaluate a dispersal response to bug density. The lower box is box 1 seen in a plan view to show the location of the vertical wooden partitions in three corners offered as a refuge to the kissing bugs. See text for a full description of the boxes, as well as the dimensions of the boxes and connecting tubes. Drawing by María Laura Morote of CEPAVE.
Fig. 3:
location of the seven paint marks on bugs. These marks were painted on each bug to allow for an individual follow-up of bugs during the experiments. Drawing by María Laura Morote of CEPAVE.
Fig. 4:
hamsters’ irritability scores as a function of bug density. This graph shows the experimental results for stage 5 nymphs and adults pooled. White circles are the original experimental values for all days and all replicates (they were slightly displaced horizontally to avoid overlap). Black squares are the experimental values averaged over all days and all replicates, and their vertical bars are the 95% confidence intervals (CI). Solid lines correspond to the fit to the natural growth model (blue; Irr = 5.09029*(1-exp(-0.04658*Dens)), and to the 2nd degree polynomial function (red; Irr = -0.0035279+0.3093827*Dens^2-1.5601374*Dens). For the second-degree polynomial fit p = 0.0197 for parameter a, p = 0.0136 for parameter b, and p = 0.1068 for parameter c; the R 2 value was 0.9812. For the natural growth model fit, p = 0.0196 for parameter a, and p = 0.1617 for parameter b, with a pseudo R 2 value of 0.9811 (using the McFadden approximation).
Fig. 5:
average blood meal size (BMS) ingested per individual (mg). The results correspond to each of the three experimental days (top row label), as a function of bug density (bugs/hamster), separately for stage 5 nymphs (left graph) and adults (right graph).
Fig. 6:
average blood meal size (BMS) ingested per individual (mg). The results correspond to stage 5 nymphs as a function of the average proportion of bugs that succeed to feed per day, and for each of the five experimental densities used (green top row label in the left-most graph), and for each average irritability score of the hamster (yellow top row label in the right-most graph). All linear regressions as a function of density were statistically significant except the one for density 60; the p-values and the adjusted R 2 were: p = 0.027 and R 2 = 0.5708, p = 7.248E-05 and R 2 = 0.7874, p = 3.789E-05 and R 2 = 0.8128, p = 0.0081 and R 2 = 0.4722, p = 0.5812 and R 2 = 0.2524, for densities 10, 20, 30, 40, and 60, respectively. The linear regressions as a function of irritability were also all statistically significant, except for irritability= 1 (p = 0.388 and R 2 = -0.013): p = 0.072 and R 2 = -0.6203, p = 0.072 and R 2 = -0.6203, p = 0.072 and R 2 = -0.6203, p = 0.072 and R 2 = -0.6203, p = 0.072 and R 2 = -0.6203, for irritabilities 2, 3, 4, 5 and 7, respectively.
Fig. 7:
average blood meal size (BMS) ingested (mg) per day. The results correspond to stage 5 nymphs that did not move between boxes as a function of density (left-most graph), and of the irritability scores of the hamster (right-most graph).
Fig. 8:
average blood meal size (BMS) ingested (mg) per day. The results correspond to adults that did not move between boxes as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 9:
average stage 5 nymphs molting time (days). The results correspond to average stage 5 nymphs molting time into adults as a function of density (left-most graph), and of the irritability scores of the hamster (right-most graph).
Fig. 10:
average molting success (%). The results correspond to the average molting success of stage 5 nymphs into adults as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 11:
average proportion of individuals surviving. The results correspond to the average proportion of individuals surviving in a three-day period as a function of bug density, separately for stage 5 nymphs, and for adults. Each point is the average for all replicates of each bug density.
Fig. 12:
overall proportion of female adults dying. The results correspond to the proportion of female adults dying in a three-week period as a function of density (left graph), and as a function of the hamster’s irritability score.
Fig. 13:
average weekly fecundity (eggs/female/week). The results correspond to the average fecundity in each week (top row labels) of the three-week observational period as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 14:
average total fecundity (eggs/female/life). The results correspond to the average total fecundity in a three-week observational period) as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 15:
average daily proportion of female adults moving to another box. The results correspond to the average daily proportion of female adults moving to another box as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 16:
average daily proportion of male adults moving to another box. The results correspond to the average daily proportion of male adults moving to another box as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph).
Fig. 17:
average of the net reproductive rate (R’ o ). The results correspond to the average of the proxy of the net reproductive rate as a function of density (left-most graph), and of the irritability score of the hamster (right-most graph). Red crosses are the original experimental values for all days and all replicates (they were slightly displaced horizontally to avoid overlap). Black circles are the experimental values averaged over all days and all replicates, and their vertical bars are the 95% confidence intervals (for Density =10, and Irritability = 1, due to the highly variable the R’ o values, the y-axis was truncated to facilitate visualization). Solid blue lines correspond to the fit to the power model (R’ o = 464.361*Dens -1.731), and R’ o = 10.9319*Irrit -1.4834). The p-values of the b coefficient of the power model were highly significant: p = 0.18483, and p = 0.00563, for a and b for R 0 as a function of density, and p = 2.01e-05, and p = 0.000536 for R 0 as a function of irritability.
Fig. 18:
combined effect of the proportion of stage 5 nymphs that fed and density of stage 5 nymphs/hamster, on blood meal size (BMS). The numerical values of the contour lines (as well as the figure’s colour scale) correspond to BMS (average in mg/individual). The x-axis is an experimental density index (x= 1, 2, 3, 4, 5) that corresponds to Densities = 10, 20, 30, 40, and 60, respectively). All variables depict the results for trial day 1.
Fig. 19:
irritability score of the hamsters as a function of total blood volume drained (mg) from the hamsters. The results correspond to the average irritability score of the hamsters, using a pool of stage 5 nymphs and adults, in the 3-days experimental period, as a function of total blood volume drained from the hamsters. The black dots are the laboratory values for each density and each replicate. The black line is the fit to a natural growth (monomolecular) model of the form: y = a*(1-exp(-b*x)); the value of the parameter a (asymptotic irritability score for very high blood drainage) was 6.17 and was statistically significant (p = 0.000251); the value of the parameter b (rate of increase of the irritability score with blood drainage) was 0.00058 and was also statistically significant (p = 0.0308). The light blue area is the 90% confidence interval calculated from the natural growth model.
Fig. 20:
identification of the density-dependent mechanisms of the population regulation process in Rhodnius Prolixus. The results correspond, using as a template our hypothesis as given in Fig. 1, identifying those mechanisms that proved to have some degree of effectiveness. S: statistically significant; NS: not statistically significant; S/NS: statistical significance observed only in a given stage (or day or week). The small graphs inserted in Fig. 20 have as x-axis the kissing bug densities per hamster, and their y-axis is represented by the density-dependent variable names given in the small internal boxes (transferred from the template of our hypothesis as given in Fig. 1).
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