The persistence of bodies such as nucleoli during the cell cycle supports the idea that nucleolar material does not completely break during metaphase and anaphase. The functional significance of these persistent bodies is still unclear. Cytochemical analyses in seminiferous triatomine tubule cells revealed that nucleolus may not disappear completely during spermatogenesis, remaining in the form of small pre nucleolar corpuscles [1, 2]. In the present study it was analyzed, by conventional techniques of transmission electron microscope, spermatogenic cells of three triatomine species: Panstrongylus megistus (fig. AD), Rhodnius pallescens (fig. E-G) and Triatoma infestans (fig. H-J), in purpose to prove "nucleolar persistence" phenomenon during spermiogenesis. The ultrastructural analyses of these species confirmed the presence of nucleolus and its products during spermiogenesis until axonema formation and in the spermatid elongation. In P. megistus (fig. A) and T. infestans (fig. H), early spermatid nucleoli present appearance reticulated. In P. megistus (fig. B), nucleolonema is clear-cut and in T. infestans (fig. H) there is distinction among fibrillar center and granular components. The nucleolus of R. pallescens (fig. E, F) reveals appearance compact. During spermatic differentiation of the three triatomine species, nucleolus shows fragmented. In P. megistus was possible to observe electron dense corpuscles (fragmented nucleolus) migrating to axonema region (fig. C, D). In R. pallescens these corpuscles have a casually distribution (fig. F, G) and, in T. infestans (fig. I, J), they are at nuclear envelope periphery. Therefore, "nucleolar persistence" phenomenon and the post meiotic reactivation hypothesis for rRNA genes, during triatomine spermiogenesis, already observed by cytochemical analyses [1, 2, 3, 4], were corroborated in the present study by ultrastructural analyses. These findings reinforced the idea of rRNA synthesis in gametogenesis is very important to the early spermiogenesis phases and, possibly, this mechanism is universal among sexed reproduction organisms.

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