Experimental Hybrids of the Triatoma brasiliensis Species Complex Show Higher Susceptibility to the Trypanosoma cruzi Infection Than Their Parentals.

The Triatoma brasiliensis species complex is a monophyletic group encompassing two subspecies and six species. Recently, a hybrid zone of members of this complex was recorded in the state of Pernambuco. Questions concerning the capability of the hybrids to become infected with Trypanosoma cruzi have been raised. This study aimed to compare the susceptibility of Triatoma b. brasiliensis, Triatoma juazeirensis, and their experimental hybrids to infection with T. cruzi. We infected the parentals and their experimental hybrids (obtained through reciprocal crosses) through artificial feeding with citrated rabbit blood, to which the TcI 0354 strain of T. cruzi had been added. The insects were weighed before and after feeding on the rabbit blood, and then they were dissected on the 10th, 20th, and 30th day after infection. Both the hybrids and the parentals remained infected throughout the experiment. The parasite was mostly found in the epimastigote form. The number of epimastigotes was significantly lower in the stomach and small intestine of T. juazeirensis than in the hybrids or in T. b. brasiliensis. A significantly higher percentage of metacyclic trypomastigotes was detected in the small intestine and rectum of the hybrids. Hybrids demonstrated higher susceptibility to the TcI 0354 strain than their parentals, opening up new avenues to be investigated.

Unraveling the Sexual Dimorphism of First Instar Nymphs of the Giant Stick Insect, Cladomorphus phyllinus Gray, 1835, from the Atlantic Forest, Brazil.

The first instar nymphs, both male and female, of the giant stick insect Cladomorphus phyllinus Gray, 1835 were carefully described and measured, revealing a remarkable sexual dimorphism that is considered rare among insects and is poorly explored in the order Phasmida. The studied F1 nymphs originated in captivity from eggs laid by a coupled female specimen collected in the Atlantic Forest in the vicinity of Petrópolis city, state of Rio de Janeiro, Brazil. The first instar nymphs of C. phyllinus were measured and illustrated in high-resolution photographs to show the general aspects and details of sexually dimorphic traits, making clear the phenotypic differences in the sexes. A total of 100 nymphs were kept alive until morphological sexual dimorphism was confirmed and quantified. All recently hatched first instar nymphs were separated based on the presumed male and female characteristics, i.e., the presence and absence of the suture in the metanotum in the males and females, respectively, had their sexes confirmed in 100% of the specimens as previously assigned. These results confirm this new morphological trait, which here is named "alar suture" as sex-specific in the first instar nymphs, a novelty in this stage of development of sexual differentiation. In addition, the distinct conformations of the last three abdominal sternites of both sexes were recorded.

Morphological Stasis in Time? A Triatoma brasiliensis brasiliensis Study Using Geometric Morphometrics in the Long Run.

Triatoma brasiliensis brasiliensis Neiva, 1911 is one of the most important vectors of Chagas disease in the Brazilian semiarid regions in the north-east. The risk imposed by T. b. brasiliensis to the human populations, due to frequent invasions and/or colonization of the domiciles, demands constant monitoring and control actions as well as an understanding of its evolutionary process. In this context, the following research studies the pattern of shape adaptation over time using a large dataset from 102 years of specimen collections in order to identify the morphological plasticity of this vector in Brazil. This dataset was analyzed using geometric morphometrics tools and the timescale was divided into eight different groups, containing specimens from 1912 to 2014. Geometric morphometrics analysis showed an interesting morphological stasis in the wing shape of T. b. brasiliensis, which allowed us to understand the high capacity of adaptation to changes in climate condition through time, and the invasive status which Triatoma species have around the world. Moreover, these results showed novel findings as an interesting phenotypic pattern, with no modifications in more than 100 years, leading us to understand the shape evolution in Triatominae as a vector species of diseases.