Cytogenetic analysis in the spermatogenesis of Triatoma melanosoma (Reduviidae; Heteroptera)

Abstract

ABsTRACT. Triatomines are of great concern in public health because they are vectors of Chagas' disease. This study presents an analysis of the species Triatoma melanosoma. The cytogenetic characteristics of triatomines include holocentric chromosomes, post-reductional meiosis in the sex chromosomes and nucleolar fragmentation in the meiotic cycle. The methodology utilized consisted of the techniques of lactoacetic orcein staining and silver ion impregnation. The organs analyzed were adult testicles. The results enabled to classify the chromosomes by number and size, being three large, eight medium and one small heterochromosome. The three largest chromosomes and the heterochromosomes showed heteropyknotic chromatin in meiosis. The heterochromosomes in 8.05% of the cells in metaphase I behaved as pseudobivalents, contrasting with 91.95% of the cells with individualized sex chromosomes, confirming the achiasmatic nature of these chromosomes. However, the pseudobivalents occurred prominently in metaphase II (78.38%), this fact probably is related to the post-reductional nature of the sex chromosomes. The nucleolus in T. melanosoma persisted until the diplotene phase after which it began to fragment. Nucleolar corpuscles were observed in metaphases I and II and during anaphases I and II, these characteristics being related to the phenomenon of nucleolar 327 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 7 (2): 326-335 (2008) Cytogenetic analysis in the spermatogenesis of T. melanosoma persistence. In the initial spermatids, peripheral silver ion impregnation occurred, which could be analogous to the pre-nucleolar corpuscles observed after fragmentation. Thus, this study extends our knowledge of the characteristics of triatomines, in particular, heteropyknotic degree, kinetic activity, formation of sex chromosome achiasmatic pseudobivalency, confirmation of the fragmentation phenomenon, and post-meiotic nucleolar reactivation.

Nucleolar Persistence: Peculiar Characteristic of Spermatogenesis of the Vectors of Chagas Disease (Hemiptera, Triatominae)

“…10 The analysis of the nucleolar behavior during the meiosis of these bugs has highlighted that all species feature the nucleolar persistence phenomenon. Therefore, as the observed results were the same for all triatomines, we represent the Our results are in agreement with the initial works carried out for the Triatoma, [11][12][13][14][15][16][17] Meccus, 18 Rhodnius, 9,19 and Panstrongylus 9 genera, which likewise have exhibited this phenomenon during spermatogenesis of these vectors.…”

Heteropicnotic chromatin and nucleolar activity in meiosis and spermiogenesis of Limnogonus aduncus (Heteroptera, Gerridae): a stained nucleolar organizing region that can serve as a model for studying chromosome behavior

“…Data on other organisms, available in the literature (Bardella et al, 2008), support the hypothesis that in L. aduncus the NOR of a single chromosome member of the pair is active in the interphase. Also on the basis of data in the literature (Lanzone and Souza, 2006), we believe that the chromosome pair, which shows the constriction, is the same pair that in Heteropteran genus Antiteuchus carries the NOR.…”

Karyotype characterization of planthopper species Hysteropterum albaceticum Dlabola, 1983 and Agalmatium bilobum (Fieber, 1877) (Homoptera: Auchenorrhyncha: Issidae) using AgNOR-, C- and DAPI/CMA3 -banding techniques

“…It is common knowledge that the nucleolus usually disaggregates during late prophase and reorganizes at early telophase. During the diplotene/diakinesis stages of both species studied here, nucleolar material (the remnants of argentophilic proteins) was presented as numerous silver-impregnated bodies adjacent to the NOR regions of the chromosomes, the phenomenon repeatedly described in the suborder Heteroptera and known as "the nucleolar fragmentation phenomenon" (Bardella et al, 2008). In H. albaceticum, the NOR-related heterochromatin appeared to be essentially GC-rich as became evident after CMA 3 -staining.…”