Memórias do Instituto Oswaldo Cruz (Vol.92(4): 493-498, jul./aug. 1997) 

Morphological Studies on the Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae, Triatominae) Genital Structures and Eggs of Different Chromatic Forms

Jane Costa/+, Ortrud Monika Barth*, Verônica Marchon-Silva, Carlos Eduardo de Almeida**, Maria Goreti Rosa Freitas-Sibajev***, Francisco Panzera****

Coleçâo Entomológica, Departamento de Entomologia *Laboratório de Ultraestrutura Viral, Departamento de Virologia ***Laboratório de Sistemática Bioquímica, Departamento de Bioquímica e Biologia Molecular, Instituto Oswaldo Cruz, Rio de Janeiro, RJ, Brasil

**Departamento de Ecologia, Sociedade Barramansense de Ensino Superior

****Sección Genética Evolutiva, Facultad de Ciencias, Montevideo, Uruguay

Triatoma brasiliensis 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 patterns of the cuticle in different localities. Four populations were analyzed in this study: 1- Caicó, 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 cuticle 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 structural 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 or taxonomic diagnosis. By scanning electron microscopy of the egg exochorion, each cromatic population presented a distinct ornamentation pattern. The melanica population differed mainly from the other populations studied since it had about 40.6%, 69.6% and 76.6% more perforations, on each cell exochorion, than the brasiliensis, the Juazeiro and the macromelasoma populations respectively. In the melanica 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).

Key words: Triatoma brasiliensis - populations - morphology - external genital structures - eggs