3.1 Overall data
Abundances of the sensilla found for all the T. dimidiata specimens included in this study are shown in Table A1, Supplementary data. All the insect’s antennae presented three types of chemoreceptors (TH, TK, and BA) and one mechanoreceptor (BR) on the three segments. The average number of sensilla per insect was of 669.52 ± 176.45. Overall, the TH sensillum of the pedicel (P-TH) was the most abundant (183.42 ± 92.70) while the BR sensillum of the flagellum 2 (F2-BR) was the least abundant (17.45 ± 12.51). The pedicel was the segment with the highest number of sensilla (322.42 ± 115.54) while the flagellum 2 was the segment with the lowest number of sensilla (149.63 ± 54.43).
3.2. AP of T. cruzi infected and non-infected T. dimidiata
Differences of each sensillum on the three antennal segments between infected and non-infected insects in the overall population, within each sex, within each population (i.e., sylvatic, domestic, and laboratory-reared), and within each sex within each population, are summarized in Table 2.
3.2.1. Overall population. When infected and non-infected insects were compared, significantly more BA sensilla on pedicel (P-BA) and TK sensilla on flagellum 1 (F1-TK) were observed in infected insects (Kruskal–Wallis test, P = 0.007 and P = 0.01, respectively).
3.2.2. Within each sex. When infected and non-infected insects were compared for each sex (I females vs NI females; I males vs NI males), significantly less TH sensilla on pedicel (P-TH) were observed in infected females (Kruskal–Wallis test, P = 0.04). Conversely, significantly more TK sensilla on flagellum 1 (F1-TK) were observed in infected males (Kruskal–Wallis test, P = 0.008).
3.2.3. Within each population. In the domestic population, when infected and non-infected insects were compared, significantly more BR sensilla on pedicel (P-BR) were observed in infected insects (Kruskal–Wallis test, P = 0.01). On the other side, significantly less TH and TK sensilla on pedicel, BR, BA, TK sensilla on flagellum 1, and BR, BA, TH sensilla on flagellum 2 were observed in infected insects (Kruskal–Wallis test, P < 0.05 in all cases). Additionally, the two-way PERMANOVA test associated the infection with T. cruzi with the AP of the domestic population (F = 7.15; P = 0.0001), while the sex and the interaction infection*sex did not have significant association with the AP (F = 1.51; P = 0.177 and F = 1.188; P = 0.299, respectively; Table 3A).
In the sylvatic population, when infected and non-infected insects were compared, significantly more BA sensilla on pedicel, BR, BA, and TK sensilla on flagellum 1, and BR, BA, TH and TK sensilla on flagellum 2 were observed in infected insects (Kruskal–Wallis test, P < 0.05 in all cases). The two-way PERMANOVA test associates the infection with T. cruzi and the sex with the AP of the sylvatic population (F = 7.41; P = 0.0001 and F = 4.28; P = 0.002, respectively), while the interaction infection*sex did not have a significant association with the AP (F = 0.368; P = 0.125; Table 3B).
Finally, in the laboratory-reared population, when infected and non-infected insects were compared, no difference in the number of sensilla were observed (Kruskal–Wallis test, P > 0.05 in all cases). In the same way, the two-way PERMANOVA test did not reveal significant association of the infection with T. cruzi, of the sex and of the interaction infection*sex with the AP of laboratory-reared insects (P > 0.05; Table 3C).
3.2.4. Within each sex within each population. Differences in the abundances of each sensillum on the three antennal segments between infected and non-infected insects within each sex within each population are shown in Table A1 (Supplementary data) and are summarized in Table 2.
Domestic population. When infected and non-infected females of the domestic population were compared, significantly less TH sensilla on pedicel and flagellum 2, and BA sensilla on flagellum 2 (Kruskal–Wallis, P < 0.05 in all cases) were observed. On the other side, when infected and non-infected males of the domestic population were compared, significantly more BR sensilla on pedicel (P-BR) (Kruskal–Wallis test, P = 0.01) were observed. Moreover, when infected and non-infected males of the domestic population were compared, significantly less BR sensilla on flagellum 1 and flagellum 2, and BA sensilla on flagellum 2 (Kruskal–Wallis, P < 0.05 in all cases) were observed.
Sylvatic population. When infected and non-infected females of the sylvatic population were compared, significantly more BA sensilla on the three segments of the antennae, BR sensilla on flagellum 1 and flagellum 2, and TK sensilla on flagellum 2 (Kruskal–Wallis test, P < 0.05 in all cases) were observed. On the other side, when infected and non-infected males of the sylvatic population were compared, significantly more BA sensilla on pedicel, BR and TK sensilla on flagellum 1, and BR and TH sensilla on flagellum 2 (Kruskal–Wallis test, P < 0.05 in all cases) were observed.
Laboratory-reared population. In the laboratory-reared population, there were no differences in the abundance of each sensillum between infected and non-infected females and between infected and non-infected males (Kruskal–Wallis test, P > 0.05).
3.3. Sexual dimorphism of T. cruzi infected and non-infected insects
Differences in the abundances of each sensillum between non-infected females and males, and between infected females and males in the overall population, and within each population, are summarized in Table 4.
3.3.1. Overall population. When non-infected females and males were compared, no significant difference in the abundance of each sensillum was observed (Kruskal–Wallis test, P > 0.05). However, when infected females and males were compared, significantly more TH sensilla on pedicel (P-TH) was observed in males (Kruskal–Wallis test, P = 0.002).
3.3.2. Domestic population. When non-infected females and males were compared, no significant difference in the abundance of each sensillum was observed (Kruskal–Wallis test, P > 0.05). However, when infected females and males were compared, significantly more TH sensilla on flagellum 1 (F1-TH) was observed in males (Kruskal–Wallis test, P = 0.01).
3.3.3. Sylvatic population. When non-infected females and males were compared, significantly more TH sensilla on pedicel (P-TH) and flagellum 1 (F1-TH) were observed in males (Kruskal–Wallis test, P = 0.02 and P = 0.003, respectively).
When infected females and males were compared, the significant difference in the abundance of TH sensilla on pedicel (P-TH) was still observed (Kruskal–Wallis test, P = 0.04), while the difference in the abundance of TH sensilla on flagellum 1 (F1-TH) was not observed anymore. However, significantly more BA sensilla on pedicel (P-BA) and flagellum 1 (F1-BA) were observed in females (Kruskal–Wallis test, P = 0.003 and P = 0.04, respectively).
3.3.4. Laboratory-reared population. In the laboratory-reared population, there was no sexual dimorphism in infected and non-infected insects (Kruskal–Wallis test, P > 0.05).