CONICET | Buscador de Institutos y Recursos Humanos

The cuticular hydrocarbon (CHC) pattern is a useful taxonomic character, and has been widely employed to discriminate blood-sucking insect complexes of mosquitoes, triatomines and flies. Triatomine CHC show characteristic profiles, with carbon number ranging from 18 to more than 40. They were identified as a mixture of straight chains together with methyl-branched chains, with one up to four methyl groups terminal and internally located at specific insertion points. Triatoma dimidiata and T. infestans (Hemiptera: Reduviidae: Triatominae) are two out of three major vectors of Chagas disease. Chagas disease affects 11 M people in Latin America, with 60 M at risk of infection, the causative agent of the disease is the kynetoplastid parasite Trypanosoma cruzi. T. dimidiata is widely distributed from central Mexico to Central America and Northern South America. Due to its large variability, the species was split and remerged several times since it was first described. T. dimidiata is still considered a single but very variable species, although growing cumulative evidence suggest that its taxonomic status should be reconsidered. T. infestans has an extensive distribution from Peru to Central Argentina in South America. Based on its predominant habitats, it was considered a homogeneous species. However, recent extensive multidisciplinary research showed that the species is divided in several discrete groups, genetically isolated. In this study we addressed a comprehensive CHC phenotype characterization of both species in order to help clarify the species taxonomic status, dispersal and domiciliation, aimed to contribute to Chagas disease control efforts. INSECTS T. infestans and T. dimidiata adult specimens were collected from most of their geographic distribution (see corresponding maps). HYDROCARBON ANALYSES Wing lipids were extracted with hexane (6 ml/g) 24 h; hydrocarbons were separated by column chromatography eluting with hexane, and analyzed by capillary gas chromatography (CGC) in a 6890 Hewlett-Packard gas chromatograph with a non-polar DB-5 capillary column (30 m x 0.32 mm I.D.) and oven temperature program. MULTIVARIATE ANALYSIS For each sample, the areas of hydrocarbon peaks were expressed as percentage values and subjected to arcsine transformation. Linear stepwise discriminant analysis (DA) was performed using hydrocarbons as variables and states/provinces as populations. Wilks' l statistic was used as a discrimination significance measure. Cross-validation method was applied on DA classification results to assess the goodness of the discriminant functions. UPGMA dendrograms were use to show population relationships. Conclusion T dimidiata CHC multivariate analyses separate the species in five groups. Groups A, B1 and B2 correspond to subspecies T. d. maculipennis, T. d. dimidiata and T. d. capitata respectively (1). Group C correspond to an undefined subspecies. Group D (insects from Belize and Lanquin caves), show a high degree of differentiation, and should be considered a distinct species. Present results both revalidate previous studies by Usinger (1), and also contribute to resolve the taxonomic status of T. dimidiata by adding new taxons (1 subspecies and 1 species). T. infestans The DA shows a non homogeneous species divided in two major groups: The Andean group ( Central and Western Bolivia populations) and the Non-Andean group (the rest of Bolivia and the entire Argentina and Paraguay populations). The cuticular hydrocarbon pattern resulted a useful taxonomic marker to discern intraspecific relationships in triatomines