Cytotaxonomy of Dipetalogaster maxima Uhler, 1894 (Hemiptera, Reduviidae, Triatominae) / Citotaxonomia de Dipetalogaster maxima Uhler, 1894 (Hemiptera, Reduviidae, Triatominae)

Abstract The Triatomini tribe consists of ten genera and is regarded as one of the most important tribes from epidemiological point of view. The genus Dipetalogaster Usinger, 1939 is composed only by the species Dipetalogaster maxima Uhler, 1894. This triatomine is exclusive of the Mexico and is a potential vector for Chagas disease. Besides the epidemiological importance, the insects of the Triatominae subfamily are important biological models for cytogenetic studies. Therefore, in order to contribute to the knowledge on the reproductive biology and assist in citotaxonomy of D. maxima, this study aimed to describe spermatogenesis, as well as confirm the karyotype and heterochromatic patterns of this Mexican triatomine species. The seminiferous tubules were torn, fixed to a cover slip and underwent the cytogenetic technique of Lacto-acetic orcein and C-banding. Through the cytogenetics analysis of testicular material D. maxima it was possible to confirm the karyotype (2n = 22), describe the stages of spermatogenesis and characterize the heterochromatic pattern (restricted to sex chromosome Y) of the species. D. maxima showed the same arrangement of heterochromatin described for Triatoma lecticularia (Stål, 1859) (a species that occur in United States of American and Mexico and is phylogenetically related with D. maxima), highlighting the importance of this analysis as an optimization tool to explore phylogenetic correlations.

Resumo A tribo Triatomini consiste em dez gêneros e é considerada uma das tribos mais importantes do ponto de vista epidemiológico. O gênero Dipetalogaster Usinger, 1939 é composto apenas pela espécie Dipetalogaster maxima Uhler, 1894. Este triatomíneo é exclusivo do México e é um vetor potencial da doença de Chagas. Além da importância epidemiológica, os insetos da subfamília Triatominae são importantes modelos biológicos para estudos citogenéticos. Portanto, a fim de contribuir para o conhecimento da biologia reprodutiva e complementar o conceito específico de D. maxima, este trabalho objetivou descrever a espermatogênese, bem como confirmar o padrão cariotípico e heterocromático desta espécie mexicana, com foco citotaxonômico. Os túbulos seminíferos foram dilacerados, fixados em uma lamínula e submetidos à técnica citogenética de Orceína lacto-acética e Bandamento-C. Por meio da análise citogenética do material testicular de D. maxima foi possível confirmar o cariótipo (2n = 22), descrever os estágios da espermatogênese e caracterizar o padrão heterocromático (restrito ao cromossomo Y sexual) da espécie. D. maxima apresentou o mesmo arranjo de heterocromatina descrito para Triatoma lecticularia (Stål, 1859) (espécie que ocorre no México e nos Estados Unidos da América, filogeneticamente relacionada com D. maxima), destacando a importância desta técnica como ferramenta para explorar correlações filogenéticas.

Cytotaxonomy of Dipetalogaster maxima Uhler, 1894 (Hemiptera, Reduviidae, Triatominae)

Abstract The Triatomini tribe consists of ten genera and is regarded as one of the most important tribes from epidemiological point of view. The genus Dipetalogaster Usinger, 1939 is composed only by the species Dipetalogaster maxima Uhler, 1894. This triatomine is exclusive of the Mexico and is a potential vector for Chagas disease. Besides the epidemiological importance, the insects of the Triatominae subfamily are important biological models for cytogenetic studies. Therefore, in order to contribute to the knowledge on the reproductive biology and assist in citotaxonomy of D. maxima, this study aimed to describe spermatogenesis, as well as confirm the karyotype and heterochromatic patterns of this Mexican triatomine species. The seminiferous tubules were torn, fixed to a cover slip and underwent the cytogenetic technique of Lacto-acetic orcein and C-banding. Through the cytogenetics analysis of testicular material D. maxima it was possible to confirm the karyotype (2n = 22), describe the stages of spermatogenesis and characterize the heterochromatic pattern (restricted to sex chromosome Y) of the species. D. maxima showed the same arrangement of heterochromatin described for Triatoma lecticularia (Stål, 1859) (a species that occur in United States of American and Mexico and is phylogenetically related with D. maxima), highlighting the importance of this analysis as an optimization tool to explore phylogenetic correlations.

Resumo A tribo Triatomini consiste em dez gêneros e é considerada uma das tribos mais importantes do ponto de vista epidemiológico. O gênero Dipetalogaster Usinger, 1939 é composto apenas pela espécie Dipetalogaster maxima Uhler, 1894. Este triatomíneo é exclusivo do México e é um vetor potencial da doença de Chagas. Além da importância epidemiológica, os insetos da subfamília Triatominae são importantes modelos biológicos para estudos citogenéticos. Portanto, a fim de contribuir para o conhecimento da biologia reprodutiva e complementar o conceito específico de D. maxima, este trabalho objetivou descrever a espermatogênese, bem como confirmar o padrão cariotípico e heterocromático desta espécie mexicana, com foco citotaxonômico. Os túbulos seminíferos foram dilacerados, fixados em uma lamínula e submetidos à técnica citogenética de Orceína lacto-acética e Bandamento-C. Por meio da análise citogenética do material testicular de D. maxima foi possível confirmar o cariótipo (2n = 22), descrever os estágios da espermatogênese e caracterizar o padrão heterocromático (restrito ao cromossomo Y sexual) da espécie. D. maxima apresentou o mesmo arranjo de heterocromatina descrito para Triatoma lecticularia (Stål, 1859) (espécie que ocorre no México e nos Estados Unidos da América, filogeneticamente relacionada com D. maxima), destacando a importância desta técnica como ferramenta para explorar correlações filogenéticas.

Programmed cell death in salivary glands of Drosophila arizonae and Drosophila mulleri

Programmed cell death (PCD) in insect metamorphosis assumes a great diversity of morphology and controlling processes that are still not well understood. With the objective of obtaining information about the PCD process, salivary glands of Drosophila arizonae and D. mulleri were studied during larval-pupal development. From the results, it can be concluded that the type of the PCD that occurs in these organs is morphologically typical of apoptosis (formation of apoptotic nuclei, followed by fragmentation into apoptotic bodies). Histolysis happens in both species, between 22 and 23 h after pupation. There were no significant differences between the species studied. Apoptosis does not occur simultaneously in all cells. Cytoplasmic acid phosphatase activity gradually increases during development, suggesting the existence of acid phosphatases that are only expressed during the apoptotic stage. Twenty hours after pupation, salivary glands already show biochemical alterations relative to nuclear permeability such as acidification, possibly due to the fusion of lysosomes with the nucleus a few hours before apoptosis. Autophagy seems to act together with apoptosis and has a secondary role in cell death.

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

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 lacto-acetic 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 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.

Differential characterization of holocentric chromosomes in triatomines (Heteroptera, Triatominae) using different staining techniques and fluorescent in situ hybridization

A comparative study of holocentric chromosomes in the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans was carried out in order to characterize heterochromatin, rDNA active sites and nucleolar proteins. Cytological preparations of seminiferous tubules were stained by silver impregnation, C banding, fluorochromes cma3/da and dapi/da, and fluorescent in situ hybridization (FISH) with Drosophila melanogaster 28S rDNA probe. Our results showed interesting aspects of the organization of chromatin and chromosomes in the meiotic cells of these insects. In R. pallescens, sex chromosomes (X, Y) were distinct from autosomes, when submitted to silver impregnation, C banding, CMA3 staining, and FISH, confirming that these chromosomes bear nucleolar organizer regions (NORs). In P. megistus, two of the three sex chromosomes were CMA3/DAPI-; at early meiotic prophase and at diakinesis, silver impregnation corresponded with FISH signals, indicating that in this species, two chromosomes (probably a sex chromosome and an autosome) bear NORs. In T. infestans, silver nitrate and FISH also stained corresponding areas on meiotic chromosomes. Our data suggest that in triatomines, in general, the number and location of NORs are species-specific. These regions may be considered important chromosome markers for comparative studies to improve the understanding of evolutionary mechanisms in these hematophagous insects.

Phylogenetic approach to the study of Triatomines (Triatominae, Heteroptera)

Os triatomíneos são insetos pertencentes à ordem Hemiptera, subordem Heteroptera, família Reduviidae e subfamília Triatominae. Todos os membros desta subfamília são hematófagos. Os triatomíneos surgiram a partir de reduvídeos predadores e provavelmente têm origem polifilética. A combinação dos fatores anatômicos, fisiológicos e etológicos presentes no grupo, bem como os caracteres plésio e apomórficos que diferenciam as cinco tribos e os quatorze gêneros de triatomíneos reforçam a hipótese polifilética. As tribos Rhodniini, Cavernicolini, Bolboderini, Linshcosteini e Alberproseniini constituem grupos monofiléticos, per si, enquanto a tribo Triatomini é considerada polifilética. O Novo Mundo é claramente o centro de diversidade dos triatomíneos e possivelmente é a região de sua origem. Entre as aproximadamente 129 espécies desses insetos, 105 ocorrem somente nas Américas. Atualmente, os triatomíneos são considerados um grupo polifilético, definido com base em seus caracteres apomórficos convergentes relacionados à hematofagia. Acredita-se que este hábito alimentar tenha surgido várias vezes nos Reduviidae durante sua evolução. O presente trabalho faz uma revisão sobre a filogenia destes vetores da Doença de Chagas, aborda tópicos como a origem da hematofagia nos triatomíneos e ancestralidade proposta para o grupo.