Isoenzymes detect variation in population of Triatoma brasiliensis (Hemiptera: Reduviidae: Triatominae)

Triatoma brasiliens is one of the most important vectors of Chagas diseases in the semiarid zone of the northeast of Brazil. Intraspecific morphological and behavioural variation has been reported for different populations. Results for four distinct populations using eight isoenzymes are reported here. The literature descibes three subspecies: T. brasiliensis Neiva, 1991; T. brasiliensis melanica Neiva & Lent, 1941 and T. brasiliensis macromelasoma Galvao, 1956. These subspecies differ mainly in their cuticle colour pattern and were regarded as synonyms by Lent and Wygodzinsky (1979). In order to evaluate whether the chromatic pattern is a morphological variation of different melanic forms within T. brasiliensis or due to interspecific variation, field collections were performed in localities where these three subspecies have been described: Caico (Rio Grande do Norte), the type-locality for T. b. brasileiensis; Petrolina (Pernambuco) for T. B. macromelasoma and Espinosa (Minas Gerais) for T. b. melanica. A fourth distinct chromatic pattern was found in Juazeiro (Bahia). A total of nine loci were studied. Values of Nei's genetic distance (D) were calculated. T. b. brasiliensis and T. b. macromelasoma are the closest populations with a D=0.295. T. b. melanica had a Dò0.537 when compared to the others, a distance in ther range of interspecific variation for other triatomine species.

Morphological studies on the Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae, Triatominae) genital structures and eggs of different chromatic forms

Triatoma brasiliens is considered one of the most important Chagas disease vectors being a wide-spread species in semiarid areas of northeastern Brazil. The species displays distinct chromatic pattern of the cutile in different localities. Four populations were analysed in this study: 1-Caico, Rio Grande do Norte, it will be called the brasiliensis population; 2-Espinosa, Minas Gerais, the melanica population; 3-Petrolina, Pernambuco, the macromelasoma population, and 4-Juazeiro, Bahia, the darker one in overall cutile coloration, the Juazeiro population. In order to differentiate the four populations of T. brasiliensis, a comparative morphological analysis of external genital structures and of eggs were carried out. The analysis of the male genital structures evidenced minor individual stuctural variations that did not correlate with chromatic differences or the geographical origins, emphasizing the importance of examining sufficiently large and representative samples before using minor genital variations for taxonomic diagnosis. By scanning electron microscopy of the egg exochorion, each chromatic population presented a distinct ornamentation pattern. The melancia population differed mainly from the other populations studied since it had about 40.6 per cent, 69.6 per cent and 76.6 per cent more perforations, on each cell exochorion, than the brasiliensis, the Juazeiro and the macromelasoma populations respectively. In the melancia population the perforation layout is also peculiar, with densely distributed perforations over all the egg surface. Morphometric measures of the eggs showed statistically significant differences: the macromelasoma population presented the longest length (2.43 mm) while the shortest was recorded in the brasiliensis population (2.29 mm).