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.

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.

No abstract

No abstract

ABSTRACT. Triatoma melanocephala is a rare species of Hemiptera. It belonged to the Brasiliensis subcomplex and presents morphological characteristics very close to those of Triatoma vitticeps. We investigated spermatogenesis of T. melanocephala and compared it with that of T. vitticeps in order to determine whether these organisms have similar cytogenetic characteristics. Lacto-acetic orcein staining was used to observe all stages of meiosis. These two species were found to have the same karyotype (2n = 20A + X 1 X 2 X 3 Y), heteropycnotic corpuscles in the polyploid spermatogonial cells, interfasic and profasic nucleus, and chromocenter with four sex chromosomes during prophase. Thus, we conclude that besides the morphologic similarity of T. melanocephala with T. vitticeps, they also have similar spermatogenesis and cytogenetics.

No abstract

No abstract

ABSTRACT. This study describes spermatogenesis in Triatoma vandae and the nucleolar behavior of T. vandae and Triatoma williami, with a cytotaxonomic focus. Analysis of mitotic and meiotic metaphases of T. vandae confirms the species karyotype. T. vandae presents some characteristics during meiosis that differentiate it from T. williami, including the presence of a chromocenter with two sex chromosomes individualized during early prophase, and the presence of a bi-or tripartite corpuscle in polyploid nuclei. It was possible to observe the compaction of chromatin during prophase resulting in holocentric chromosomes. During metaphase, the autosomes presented a ring shape and the sex chromosomes were in the center of the ring. These chromosomes were separated in anaphase. Although it is common, we did not observe the phenomenon of late migration of the sex chromosomes. By means of silver ion impregnation it was possible to describe nucleologenesis in T. vandae and T. williami.