ABSTRACT
Triatoma melanocephalae T. lentisão espécies crípticas de triatomíneos pertencentes ao subcomplexo Brasiliensis. Esses organismos foram agrupados no subcomplexo apenas por caracteres morfológicos e pela disposição geográfica. Sendo assim, estudos citogenéticos são considerados como importantes ferramentas na classificação dos triatomíneos e, com isso, podem auxiliar na criação de um plano de profilaxia da doença. Por meio da técnica citogenética de impregnação por íons prata, foi possível visualizar a atividade nucleolar e as Regiões Organizadoras Nucleolares (RONs) desses insetos. T. melanocephala apresentou três RONs ativas nos autossomos durante a prófase I. T. lenti apresentou duas RONs ativas nos autossomos durante a prófase I e a metáfase I. Ambas as espécies apresentaram o fenômeno de persistência do material nucleolar encontrado em triatomíneos. Sendo assim, por meio da análise das RONs, foi possível observar que T. lenti, quando comparado com os outros organismos do subcomplexo, apresentou marcações semelhantes à T. tibiamaculata e que T. melanocephala não apresenta nenhuma relação direta com o subcomplexo.
Triatoma melanocephala and T. lenti are important vectors of Chagas disease. These cryptic species of triatomines are grouped in the subcomplex brasiliensis due only to morphological characters and geographical distribution. Cytogenetic studies are important to the classification of insects and can assist in creating a disease prevention plan. The aim of the present study was to determine nucleolar activity and nucleolus organizer regions (NORs) in these insects using the cytogenetic method of silver ion impregnation. T. melanocephala exhibited three active NORs in autosomes during prophase I. T. lentiexhibited two active NORs in autosomes during prophase I and metaphase I. Both species exhibit the persistent nucleolar material found in triatomines. The analysis of NORs in the present study revealed that T. lentiexhibited labeling similar to that found in T. tibiamaculata, which belongs to the subcomplex, whereas T. melanocephala shows no direct relationship with the subcomplex.
Subject(s)
Cytogenetic Analysis , Classification/methods , Triatominae/cytology , Triatominae/genetics , Chagas Disease , Disease VectorsABSTRACT
The specific identification and systematic of triatomines have been based fundamentally on morphological observations. These organisms are classified into complexes and specific subcomplexes, principally for morphological parameters and geographical disposition. The use of cytogenetic analyzes has been represented as a tool in systematic and taxonomy of triatomines. Thus, the present work, through the analysis of spermiogenesis, aims to characterize this stage of spermatogenesis in triatomines little studied, and especially to compare it among the species Triatoma lenti and T. sherlocki, to assist in the diagnosis of differentiation of these insects. The presence of the heteropyknotic corpuscle is shown as a diagnostic tool to differentiate T. sherlocki and T. lenti, since it is absent in T. lenti. The analysis of the spermiogenesis in T. sherlocki also allowed us to address morphological differences between elongating cells, which were relatively smaller and more filamentous when compared to T lenti. Furthermore, the flagellum was observed in all stages of cell differentiation and elongation. This structure, which helps in the locomotion of the sperm, is hardly observed in cytogenetic analysis, especially throughout spermiogenesis. Thus, although other comparative approaches should be taken, this paper allowed emphasizing the analysis of spermiogenesis as an important cytotaxonomic tool that assists in the differentiation of morphologically related species, such as T. lenti and T. sherlocki.
Subject(s)
Spermatogenesis/physiology , Triatoma/physiology , Animals , Brazil , Cytogenetic Analysis , Male , Species Specificity , Sperm Tail/physiology , Sperm Tail/ultrastructure , Spermatids/physiology , Spermatids/ultrastructure , Triatoma/classificationABSTRACT
Triatoma lenti and Triatoma sherlocki are hemipterans that belong to the brasiliensis subcomplex. In triatomines, the constitutive heterochromatin pattern is species-specific and allows, in many cases, for the grouping of species. Thus, we cytogenetically analyzed T. sherlocki and T. lenti using C-banding, and we compared the results with previous ones obtained in other species of the brasiliensis subcomplex. Both species were found to have a male diploid chromosome number of 22 chromosomes (2n=20A+XY) with heterochromatic blocks at one or both chromosomal ends of all autosomal pairs. During early meiotic prophase, they showed a large heteropycnotic chromocenter constituted by the association of both sex chromosomes plus two autosomal pairs and many heterochromatic blocks dispersed inside the nucleus. All of these cytogenetic characteristics are similar to those observed in other species of brasiliensis subcomplex, results which confirm the grouping of T. sherlocki and T. lenti within this subcomplex. However, we emphasize the importance of other approaches, such as molecular analysis, to confirm the placement of T. lenti within the brasiliensis subcomplex.
Subject(s)
Heterochromatin/genetics , Triatoma/genetics , Animals , Chromosomes, Insect , Diploidy , Heterochromatin/metabolism , Male , Meiosis , ProphaseABSTRACT
Triatoma melanocephala is a rare species of Hemiptera that belongs to the Brasiliensis subcomplex. This subcomplex is composed of cryptic species, and the basic number of chromosomes for triatomines of this subcomplex is 2n = 22; however, T. melanocephala showed a karyotype of 2n = 24 (20A + X(1)X(2)X(3)Y). Thus, this study allowed us to describe the karyotype of the species and, more specifically, to propose the exclusion of T. melanocephala, as well as T. vitticeps and T. tibiamaculata, which also has fragmentation of the X chromosome, from the Brasiliensis subcomplex.
