Ecotope effect in Triatoma brasiliensis (Hemiptera: Reduviidae) suggests phenotypic plasticity rather than adaptation.

Triatoma brasiliensis (Hemiptera: Reduviidae) is an important vector of Chagas' disease in both sylvatic and peridomestic ecotopes. Discriminating between these populations of Triatominae has been proposed as a means of investigating re-infestation rates of human dwellings. Geometric morphometrics have been widely applied in the study of Triatominae polymorphisms at species and population levels. This study characterizes morphometric differences between sylvatic and peridomestic populations, as well as between sexes in T. brasiliensis specimens from Jaguaruana, Ceará, in northeastern Brazil. No differences in either the shape or size of the cephalic capsule were apparent between sexes or ecotopes. However, the wings showed differentiation in shape and size. Sexual dimorphism was detected, with females presenting significantly higher values and conformations. Size differentiation was also evident, with sylvatic specimens being generally larger than peridomestic examples. These results indicate that differences in the wings of T. brasiliensis may be related to the existence of phenotypic plasticity, and variations in size and shape may be associated with different ecotopes, possibly as a result of conditions in each micro-habitat, such as temperature, relative humidity, food supply and density.

Morphology of reproductive accessory glands in eight species of blood-feeding Hemiptera (Hemiptera, Reduviidae) insect vectors of Chagas disease.

This paper documents the morphology of previously undescribed adult reproductive accessory glands in eight species of blood-feeding Hemiptera, vectors of Chagas disease. These species are three Triatoma (T. dimidiata, T. klugi, T. sordida), three Rhodnius (R. brethesi, R. nasutus, R. pictipes), and one species each from Nesotriatoma (N. bruneri) and Panstrongylus (P. megistus). This survey shows that the male reproductive systems between species of four genera of Reduviidae adhere to the same general plan seen in previously described vectors of Chagas disease. This morphological similarity suggests that reproductive success of the male is contingent on the delivery of a vital set of male accessory gland secretions to the female in conjunction with material from the testes and seminal vesicle. However, variations were observed in the accessory glands of females, especially at the level of the genus. The spermathecae are morphologically distinct, and the posterior accessory glands are absent in some. The differences in spermathecae morphology likely reflect physiological adaptations associated with speciation driven by cryptic female choice in which the female determines which sperm are used for fertilization. Differences in the posterior reproductive accessory gland can be correlated with variations in ovipositioning behaviour. Since reproductive physiology is important for species success, this information also augments epidemiological studies by providing a comparison to R. prolixus, a Chagas disease vector for which the physiology is well known.

Genetic polymorphism in Trypanosoma cruzi I isolated from Brazilian Northeast triatomines revealed by low-stringency single specific primer-polymerase chain reaction.

Different molecular markers have been employed for typing Trypanosoma cruzi strains from endemic areas of Chagas disease. The low-stringency single specific primer-polymerase chain reaction (LSSP-PCR) has been a sensitive and informative technique that uses the variable region of kinetoplast DNA minicircles as a genetic marker, allowing detection of DNA sequence variation. In the present study, we analyzed the intra-lineage genetic variability of the T. cruzi strains obtained from triatomine feces collected on filter paper FTA card by LSSP-PCR. The hybridization of the PCR products with a probe for the subgenus Schizotrypanum and a clone-specific probe from Dm28c confirmed the subgenus as T. (S.) cruzi and respective lineages as T. cruzi I. Phenetic analysis showed the presence of three clusters that diverged by different coefficients of similarity. Thirteen T. cruzi I genotypes were observed circulating among Triatoma pseudomaculata and Rhodnius nasutus from peridomiciliary and natural environments in five peri-urban and urban localities of Jaguaruana, Ceará, Brazil. These data indicate the importance of the circulation of T. cruzi I genotypes among T. pseudomaculata and R. nasutus in different environments and the possible risk of Chagas disease domestic transmission.

Is Rhodnius nasutus (Hemiptera; Reduviidae) changing its habitat as a consequence of human activity?

Rhodnius nasutus, a triatomine species autochthonous in the Brazilian Northeast, is primarily associated with the Copernicia prunifera palm tree (Carnauba). For the first time, the colonization of this triatomine in another tree species is reported. To investigate the existence of an infected triatomine focus located in a periurban area of the county of Jaguaruana, Ceará, situated in the Brazilian Northeast, where soil is greatly altered and natural vegetation scarce, an entomological survey was performed. During 2 consecutive days in August 2006 and 4 in December 2006, with the aid of live-bait traps, nine C. prunifera palms and seven Licania rigida trees (Oiticica), among other typical trees of the region, were sampled. In April 2007, 13 L. rigida trees and five C. prunifera palm trees were newly sampled. Considering the three investigation periods, a total of 20 R. nasutus specimens in C. prunifera and 52 in L. rigida were captured, in all developmental stages, 12.5 and 20.7%, respectively, harboring T. cruzi-like protozoa. The authors suggest that environmental damages are facilitating the ability of this species to colonize other trees besides palms.

Effects of Bayluscide WP 70 on the survival and water-leaving behaviour of Biomphalaria straminea, snail host of schistosomiasis in northeast Brazil.

The toxic and behavioural effects of niclosamide (Bayluscide WP 70) on Biomphalaria straminea from a highly endemic area of schistosomiasis in northeastern Brazil were investigated through laboratory bioassays. The LD50 and LD90 were 0.114 mg/l and 0.212 mg/l, respectively. Water-leaving behaviour occurred among 14% to 30% of the snails in the presence of sublethal doses of niclosamide and among 16% of the controls. It was concluded that both the relatively low susceptibility to niclosamide and water-leaving behaviour of local B. straminea may be responsible for the recolonization of transmission foci after mollusciciding. It was suggested that recently improved measures of snail control, such as controlled-release formulations of niclosamide and plant molluscicides should be considered in areas where snail control is recommended.

Effect of Niclosamide (Bayluscide WP 70), Anacardium occidentale hexane extract and Euphorbia splendens latex on behavior of Biomphalaria glabrata (Say, 1818), under laboratory conditions.

The repellent effect of the molluscicides Niclosamide (Bayluscide WP 70), Anacardium occidentale and the latex of Euphorbia splendens on Biomphalaria glabrata was observed through the investigation of the occurrence of escape behavior among molluscs that were exposed to dosages lower than the LD 50. The total number of individuals out of water among the surviving snails in the control group provided a "Natural Escape Index". The comparison between this total and the total number of surviving snails in each group exposed to the different dosages of the molluscicides after 24 hr provided the "Molluscicide Escape Index" and the detection of a "Repellency Range" to these snails. The escape indexes for Niclosamide, A. occidentale and E. splendens were 10%, 6.22% and 6.44% respectively. Repellency occurred at the following concentration ranges: 0.01, 0.02 and 0.03 ppm Bayluscide, 0.1, 0.2 and 0.3 ppm A. occidentale and 0.05, 0.10, 0.15 and 0.20 ppm E. splendens. The Natural Escape Index obtained in the control group was zero.