The Triatominae subfamily is comprised of 18 genera and six tribes. The tribe Rhodniini is comprised of two genera (Rhodnius and Psammolestes). Nucleolar persistence is defined by the presence of the nucleolus or nucleolar corpuscles during the meiotic metaphase. To date, this phenomenon has been described for 13 species of triatomine that are included in the genera Triatoma, Rhodnius, and Panstrongylus. Thus, because the phenomenon of nucleolar persistence has been described in only two species of the genus Rhodnius, we have analyzed the nucleolar behavior during spermatogenesis of eight species of the genus Rhodnius (R. colombiensis, R. montenegrensis, R. nasutus, R. neglectus, R. neivai, R. pictipes, R. prolixus, and R. robustus), with a focus on nucleolar persistence. By means of cytogenetic analysis with silver ions, nucleolar behavior during spermatogenesis is described in the eight species of Rhodnius analyzed. In all of them nucleolar behavior was similar and the phenomenon of nucleolar persistence was often observed. Therefore, we confirm nucleolar persistence as a peculiarity of the genus Rhodnius. However, it is emphasized that new cytogenetic analysis should be performed in the Triatominae subfamily, more specifically among the 15 genera that do not exhibit the nucleolar behavior described, in order to assess whether this phenomenon is truly a synapomorphy of these hematophagous insects.

Abstract. All species of triatomines are considered potential vectors of Chagas disease and the reproductive biology of these bugs has been studied by different approaches. In 1999, nucleolar persistence during meiosis was observed in the subfamily for the first time. Recently, it has been observed that all species within the genus Rhodnius exhibit the same phenomenon, suggesting that it may be a synapomorphy of the triatomines. Thus, this article aims to analyze the nucleolar behavior during spermatogenesis of 59 triatomine species. All analyzed species exhibited nucleolar persistence during meiosis. Recently, it has been suggested that nucleolar persistence may be fundamental for the spermatogenesis of these vectors, since it is related to the formation of the chromatoid body. Therefore, we emphasize that this phenomenon is a peculiarity of the Triatominae subfamily and that further studies are required to analyze whether the nucleolar material that persists is active.The Triatominae subfamily is composed of 150 species (148 living species and two fossils), grouped into 18 genera and five or six tribes. All triatomine species are considered potential vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease. 1Chagas disease is a neglected disease that has no cure. The main way to minimize the incidence of this disease in human populations is through vector control.1 It is estimated that more than 5 million people are infected by T. cruzi, the parasite that causes Chagas disease, and that 70 million still live at risk, which places this illness among the most serious parasitic diseases in the world.1 Thus, improving the knowledge on several fields on triatomine vector potentiality (such as ecology 2 and biology 3 ) may provide important information for control measures.The reproductive biology of these bugs has been studied by different approaches, such as cytogenetic, 4 structural, 5 and ultrastructural 6 analysis. Furthermore, the spermatogenesis of the triatomines is characterized as cystic, 5,6 and it has been suggested that, during imaginal molt (transition from the fifth instar nymph to adult), the cell division is disrupted, aiming to reduce energy costs, and the differentiation into sperm is stimulated to ensure the paternity of the adult male. 7In 1999, Tartarotti and Azeredo-Oliveira, 8 while studying the spermatogenesis of Panstrongylus megistus and Panstrongylus herreri (= Panstrongylus lignarius), noted that these triatomines exhibited a different nucleolar behavior than the one described for other eukaryotes: the nucleolus persisted during all stages of meiosis. The authors characterized this phenomenon as nucleolar persistence.Recently, Alevi and others 9 have observed that all species within the genus Rhodnius feature nucleolar persistence during meiosis as well, and they suggested that analyses of the nucleolar behavior should be carried out in a large range of species of triatomines to examine whether that characteristic is a synapomorphy of the Triatominae subfamily.Thus, this ...