Feeding behavior of Triatoma vitticeps (Reduviidae: Triatominae) in the state of Minas Gerais, Brazil

The objective of this study was to evaluate the feeding behavior of Triatoma vitticeps through the identification of its food sources and the characterization of the blood ingestion process. In addition, we aimed to verify if the saliva of this vector interferes with the perception of the host during the feedings by creating a nervous impulse. Here, we demonstrated that the T. vitticeps saliva reduces, gradually and irreversibly, the amplitude of the compound action potential of the nervous fibre, which helps decrease the perception of the insect by the host. The precipitin reaction demonstrated the feeding eclecticism of this vector, with the identification of eight food sources - most of them found simultaneously in the same insect. The analysis of the electrical signals produced by the cibarial pump during meals demonstrated that the best feeding performance of T. vitticeps nymphs that fed on pigeons is mainly due to the higher contraction frequency of the pump. The longer contact period with the host to obtain a complete meal compared with other triatominae species of the same instar could favor the occurrence of multiple blood sources in T. vitticeps under natural conditions, as it was evidenced by the precipitin test.     

Triatoma sordida St?l 1859 (Hemiptera, Reduviidae: Triatominae) in palms of northeastern Argentina.

Several palms species provide an important habitat for triatomines and associate vertebrates in tropical America. The objective of this work is to identify the triatomine species living in the palms of rural areas in the Province of Corrientes, and to estimate the potential epidemiological risk they represent for the residents of nearby houses. The survey was carried out in a palm community in Colonia Laurel, Department San Roque, Province of Corrientes, Argentina. Samplings were performed in October, November and December 1998; January, February and March 1999; May and June 1999. Thirty palms: 27 (90%) Butia yatay (Mart.) Becc. and 3 Acrocomia aculeata (Jacq.) Lodd ex Mart. were dissected. Triatoma sordida St?l 1859 was found in 96.2% of B. yatay and in all the A. aculeata palms. A total of 272 live T. sordida was collected; 36 of them (13.2%) were found in bird nests in the frond and the remainder in other locations of the tree. The mean number of triatomines per palm was 9.6 (range 1-60, mode 2). T. sordida was collected during all the sampling months and all stages were present at all seasons. The highest population density was reached in spring and the lowest in autumn. Trypanosoma cruzi was detected in 38.5% in feces of 174 examined insects and identified as such, both by microscopical examination and PCR. This is the first finding of T. sordida populations in B. yatay, an endemic palm of South America distributed in southern Brazil, Uruguay and northeastern Argentina. The high infection prevalence found in this work suggests that T. sordida plays an essential role in the maintenance of the wild T. cruzi transmission cycle in northeastern Argentina.     

Triatoma juazeirensis sp. nov. from the state of Bahia, Northeastern Brazil (Hemiptera: Reduviidae: Triatominae)

Triatoma juazeirensis, a new triatomine species from the state of Bahia, Northeastern Brazil, is described. The new species is found among rocks in sylvatic environment and in the peridomicile. Type specimens were deposited in the Entomological Collection of Oswaldo Cruz Institute-Fiocruz, Museum of Zoology of University of S?o Paulo, and Florida Museum of Natural History. T. juazeirensis can be distinguished from the other members of the T. brasiliensis species complex mainly by the overall color of the pronotum, which is dark, and by the entirely dark femora.     

The biology of three Mexican-American species of Triatominae (Hemiptera: Reduviidae): Triatoma recurva, Triatoma protracta and Triatoma rubida

The values of biological parameters related to hatching, lifespan, the number of blood meals between moults, mortality, time lapse before the beginning of feeding, feeding time and defecation delay for each instar of three Mexican-American species of Triatominae, Triatoma recurva, Triatoma protracta (former subspecies protracta) and Triatoma rubida (former subspecies uhleri), were evaluated and compared. No significant (p > 0.05) differences were recorded among the three species with respect to the average time required to hatch. This time was approximately 19 days. The average egg-to-adult development time was significantly (p < 0.05) shorter for T. rubida. The number of blood meals at each nymphal instar varied from one-five for each species. The mortality rates were higher for the first-instar nymphs of the three species studied. The mean time lapse before the beginning of feeding was between 0.3-3 min for most nymphs of all instars of each species studied. The mean feeding time was the longest for T. recurva, followed by T. protracta. The defecation delay was less than 10 min for T. recurva and T. rubida. Given these results, only T. rubida should be considered an important potential vector of Trypanosoma cruzi transmission to humans in areas of Mexico where these species exist, whereas T. recurva and T. protracta would be of secondary importance.     

Triatoma rubrovaria (Blanchard, 1843) (Hemiptera,Reduviidae, Triatominae) II: trophic resources and ecological observations of five populations collected in the State of Rio Grande do Sul,Brazil

Triatoma rubrovaria has become the most frequently captured triatomine species after the control of T. infestans in the State of Rio Grande do Sul (RS), Brazil. Isoenzymatic and chromatic studies indicate the existence of, at least, two distinct phenotypic patterns of T. rubrovaria in RS. The geographic variation noted through molecular tools may also result in distinct profiles of vectorial potentiality. In order to enhance our understanding of the bionomic knowledge of T. rubrovaria separate batches of the species were collected from different municipalities of RS distant from 72 to 332 km: Santana do Livramento (natural ecotope), Santana do Livramento (artificial ecotope), Santiago (natural ecotope), Cangu u (peridomicile) and Encruzilhada do Sul (natural ecotope). A total of 285 specimens were collected, 85 specimens kept sufficient fecal material in their guts for the precipitin analysis. The results indicated the food eclecticism for this species and the anti-rodent serum showed the highest positivity in most localities. From the total of analyzed samples, only 1.3% of unique positivity for human blood was registered, all of them for Santiago population. This reactivity to human blood may be associated to pastures activities in the field.     

Morphometric analysis of Triatoma dimidiata populations (Reduviidae:Triatominae) from Mexico and Northern Guatemala

Triatoma dimidiata is one of the major vectors of Chagas disease in Latin America. Its range includes Mexico, all countries of Central America, Colombia, and Ecuador. In light of recent genetic analysis suggesting that the possible origin of this species is the Yucatan peninsula, we have analyzed populations from the state of Yucatan, San Luis Potosi, and Veracruz in Mexico, and a population from the southern region of the Yucatan peninsula located in Northern Guatemala, the region of El Peten. Classical morphometry including principal component, discriminant, sexual dimorphism, and wing asymmetry was analyzed. San Luis Potosi and Veracruz populations were indistinguishable while clearly separate from Yucatan and Peten populations. Despite important genetic differences, Yucatan and Peten populations were highly similar. Yucatan specimens were the smallest in size, while females were larger than males in all populations. Only head characters were necessary to distinguish population level differences, although wing fluctuating asymmetry was present in all populations. These results are discussed in light of recent findings suggesting genetic polymorphism in most populations of Triatoma dimidiata south of Chiapas to Ecuador.     

Head morphology of 1st and 5th instar nymphs of Triatoma circummaculata and Triatoma rubrovaria (Hemiptera,Reduviidae)

Morphological structures of the head of 1st and 5th instar nymphs of Triatoma circummaculata and Triatoma rubrovaria were revealed by analysis using scanning electron microscopy (SEM). Differences between 1st and 5th instar nymphs of these two species were observed in the postocular callosity, the number of ommatidia and tapered hair, the small segment between antennal segments, the rostrum third segment and slit lines. These slit lines were different only in the 5th instar. Similarities observed were the presence of tapered hairs in the joints, and the type of sensilla in the antennal segments. Only the 1st instar shows anteclypeus and gena sensilla. The antennal segments comprise the following types of sensilla: basiconica, bristles type I, bristles type II, bristles type III, campaniformia, coeloconica, chemosensilla, placodea, trichobothria and trichoidea. We describe here for the first time six (3+3) sensilla basiconica on the dorsal portion of the first segment of the rostrum.     

Genetic structure of Triatoma venosa (Hemiptera: Reduviidae): molecular and morphometric evidence

Triatoma venosa presents a restricted geographical distribution in America and is considered as a secondary vector of Chagas disease in Colombia and Ecuador. A total of 120 adult insects were collected in domestic and peridomestic habitats in an endemic area of the department of Boyacá, Colombia, in order to determine their genetic structure through morphometric and molecular techniques. The head and wings of each specimen were used for the analyses of size, shape, and sexual dimorphism. A significant sexual dimorphism was found, although no differences in size among the studied groups were detected. Differences were found in the analyzed structures except for male heads. DNA was extracted from the legs in order to carry out the internal transcriber space-2 (ITS-2) amplification and the randon amplified polymorphic DNA (RAPD) analyses. Length polymorphisms were not detected in the ITS-2. Fst and Nm values were estimated (0.047 and 3.4, respectively). The high genetic flow found among the insects captured in the domicile and peridomiciliary environment does not permit a genetic differentiation, thus establishing the peridomicile as an important place for epidemiological surveillance.     

Triatoma rubrovaria (Blanchard, 1843) (Hemiptera: Reduviidae) I: isoenzymatic and chromatic patterns of five populations from the State of Rio Grande do Sul,Brazil

Triatoma rubrovaria has become the most frequently captured triatomine species since the control of T. infestans in the State of Rio Grande do Sul (RS), Brazil. In order to evaluate the genetic variability of this species, field collections were performed in four municipalities where it has been reported and distant from 75 to 322 km. Specimens were analyzed by color pattern and isoenzymes. Nine enzymatic loci were interpreted from nine enzymatic systems. The Santiago population was isolated from the others with chromatic monomorphism and diagnostic alleles at Idh and Pgm loci. The study shows the existence of, at least, two distinct populations of T. rubrovaria in RS with different phenotypic and genetic pattern.     

Glandular areas associated with the male genitalia in Triatoma rubrofasciata (Triatominae, Reduviidae, Hemiptera) and other Reduviidae

In this paper, glandular areas associated with the phallus in Triatoma rubrofasciata are described and illustrated for the first time. The glandular areas lie in the membrane surrounding the articulatory apparatus. In order to unambiguously define the locality of the respective glandular areas, some features of the pygophore-phallus connection are redescribed. A possible functional context of the gland secretions is discussed. A preliminary study of several other Reduviidae implies that the described glandular areas occur in a wider range of taxa in this group.     

Biology of Triatoma pallidipennis stal 1945 (Hemiptera: Reduviidae:Triatominae) under laboratory conditions

Aspects related to hatching, life time, mortality, feeding behaviour and fecundity for each stage of Triatoma pallidipennis life-cycle were evaluated. The hatching rate observed for 200 eggs was 60% and the average time of hatching was 18 days. Eighty nymphs (N) (40%) completed the cycle and the average time from NI to adult was 168. 7+/-11.7days. The average span in days for each stage was 18.0 for NI, 18.5 for NII, 30.0 for NIII, 35.7 for NIV and 50.1 for NV. The number of bloodmeals at each nymphal stage varied from 1 to 5. The mortality rate was 9.17 for NI, 5.5 for NII, 6.8 for NIII 4.17 for NIV and 13.04 for NV nymphs. The average number of eggs laid per female in a 9-month period was 498.6. The survival rates of adults were 357+/-217.9 and 262.53+/-167.7 for males and females respectively.     

Presence of Panstrongylus rufotuberculatus (Champion, 1899) (Hemiptera: Reduviidae: Triatominae) in Argentina.

Panstrongylus rufotuberculatus is reported for the first time in Argentina. Four adults were attracted by the light of human dwellings in Calilegua National Park, Jujuy, at 1150 masl within the subtropical humid forest. The individuals were similar to those described in the literature. The epidemiological significance of this species is very low in the area, although deforestation might increase its role in the transmission of Trypanosoma cruzi.     

Dynamics of evolution and resistance to starvation of Triatoma vitticeps (Stal 1859) (Reduviidae: Triatominae), submitted to two different regimens of food deprivation

The resistance to starvation of Triatoma vitticeps has been analyzed comparatively, according to different regimens of food deprivation under laboratory conditions. One cohort, composed of 100 specimens of each evolutionary nymphal stage, was submitted to continuous fasting until death; the second group, arranged in the same way, was fed once on chicken. Through this work, it was possible not only to compare the results obtained from the first group with other authors' results but, also, to analyze the dynamics of evolution, molting, longevity and the increase in insect longevity, in the second group. The average values recorded for survival time revealed statistical differences between the two groups. Among the important results detected, there is one that deserves to be emphasized: the incredible increase in longevity among insects that received only one feed - an average increase in survival time that reached 2.95 to 3.30 times in nymphs of 3rd and 4th stages, respectively. One 5th stage nymph survived for up to 350 days and the females may triplicate their survival rate, what represents an important epidemiological factor. The knowledge about this type of biological characteristic of T. vitticeps may contribute to prevent the domiciliation of this species, what seems to be incipient in some municipal districts, in Brazil.     

The resistance of fasting and nutritional aspects of Triatoma lecticularia (Stal, 1859) (Hemiptera, Reduviidae, Triatominae)

The resistance to fasting of Triatoma lecticularia was studied in all phases of the life cycle and the insect weighed in different nutritional situations (fed, not fed, death after starvation). The temperature and humidity levels were also recorded. The nymphal phases showed increasing resistance to fasting as demonstrated by the following averages (days) 1st 45.84; 2nd 61; 3rd 88.74; 4th 123.44; 5th 162.30. Upon the adult phase, the averages were similar to those of the 3rd stage for the male insects 88.94 and for the females 83.66. The weighing technique allowed for the measurement of the quantity of blood ingested, the weight loss during the fast and the percentage weight loss as related to the initial weight. The species is found in the Neartic region where it has been found infected with Trypanosoma cruzi and is associated with the terrestrial rodents Neotoma micropus Baird and Spermophilus variagatus (Erxelebem).     

Eye colour as a genetic marker for fertility and fecundity of Triatoma infestans (Klug, 1834) Hemiptera,Reduviidae, Triatominae

Eye colour of Triatoma infestans is controlled at a single autosomal locus, with black-eye as the dominant gene and red-eye as the recessive. Inheritance of these characters follows a classical Mendelian system, enabling eye colour to be used as a marker for studies of mating frequency. We found no significant differences in oviposition rates and egg hatching rates irrespective of parental phenotypes. Different mating schedules between red-eye and black-eye parents showed that eye colour did not affect mating competence. Females mated with a single male or with different males together or in succession produced similar numbers of fertile eggs, with the eye colour of the offspring reflecting exposure to the different males. We conclude that although a single mating can provide sufficient sperm for the whole reproductive life of the female, multiple matings can result in balanced assortative sperm usage from the spermatheca.     

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala

Triatoma nitida was found in 14 (0.4%) out of 3,726 houses located in six departments across Guatemala, which were surveyed from 1994 to 1998 by the man-hour collection method. Compared to previous information, the distribution of T. nitida in Guatemala has increased from five to nine departments; the species is present in mild climates at altitudes from 960 to 1,500 m. Fourteen percent of the intradomestic T. nitida were infected with Trypanosoma cruzi. The species was often found in conjunction with other triatomines (T. dimidiata and Rhodnius prolixus). The domestic and peridomestic presence of T. nitida in Guatemala was rare, but occasionally this species was colonizing human-made constructions. T. nitida appears to have a low importance as Chagas disease vector in Guatemala, as indicated by its scarce presence in the domestic habitats and defecation patterns. However, it clearly has potential to become a Chagas vector so we recommend an on-going study of the intradomestic presence of T. nitida following the control programs in Guatemala. Morphometric analysis of 47 T. nitida males from three localities showed quantitative differences between the populations, which indicates that geographic distance is an important factor in the structuring of T. nitida populations.     

Crossing experiments detect genetic incompatibility among populations of Triatoma brasiliensis Neiva, 1911 (Heteroptera,Reduviidae, Triatominae)

Triatoma brasiliensis is composed of at least four geographic populations (brasiliensis, melanica, macromelasoma, and juazeiro) that have distinct chromatic, morphologic, biologic and ecologic patterns, and genetic composition. Reciprocal crosses between all pairwise combinations were carried out in order to evaluate the genetic and reproductive compatibility of these four populations. The F1 individuals developed normally and the resulting adults were crossed again to test the F2 and F3 viability. Genetic incompatibility was found between melanica and brasiliensis populations.