Patterns of nucleolar activity during spermatogenesis of two triatomines,Panstrongylus megistusandP. herteri

Abstract

-The present work analyzed spermatogenesis in two species of triatomines (genus Panstrongylus) using silver-ion impregnation. The sex chromosomes of P. megistus and P. herreri had nucleolar organizing activity and became strongly impregnated during the phases of meiotic prophase I. Fragmentation of the nucleolus occurred in both species dur ing the meiotic cycle. The nucleolar region could be observed up to diakinesis in meiotic prophase after which only nucleolar bodies and fragments were seen. Postmeiotic reactivation of rRNA synthesis occurred in these two species and was probably related to cell differ entiation.

Spermatogenesis and nucleolar activity in Triatoma klugi (triatomine, Heteroptera)

“…Dispersed nucleolar bodies were observed at metaphase II in T. klugi and a large nucleolar mass was also observed during metaphase I, anaphase I and telophase I. This confirms the occurrence of "nucleolar material persistence" as suggested by Tartarotti and Azeredo-Oliveira (1999b) and provides evidence that the nucleolus does not completely disappear during meiosis in triatomines, but is reorganized from pre-existing nucleolar elements.…”

“…The same phenomenon has already been described P. megistus and P. herreri (Tartarotti and Azeredo-Oliveira, 1999b) and indicates that not all ribosomal genes are necessarily active. The presence of NORs in heterochromosomes is a common 442 Cytogenetic of Triatoma klugi phenomenon in insects and several Drosophila species, for instance, have ribosomal genes located on their sex chromosomes (Bicudo, 1984).…”

“…Nucleolar bodies have also been observed in testis polyploid nuclei of Panstrongylus megistus and P. Herreri (Tartarotti and Azeredo-Oliveira, 1999b). The increase in nucleolar bodies in polyploid nuclei may be related to increased rRNA synthesis (Tavares and Azeredo-Oliveira, 1997).…”

“…In the subfamily Triatominae the nucleolus persists during meiosis (Tartarotti and Azeredo-Oliveira, 1999b;Morielle and Azeredo-Oliveira, 2004). Some studies performed in insects indicated that silver nitrate stained structures could represent kinetochore or centromere material (Suja et al, 1991;Rufas and Gosálvez, 1982).…”

Nucleolar Persistence during Meiosis of the Triatomines (Hemiptera, Triatominae) – An Editorial Review

“…In addition to the epidemiological importance, these insects are important models for cellular studies because they present some peculiarities as holocentric chromosomes [2], meiosis inverted to the sex chromosomes [2] and persistence nucleolar during meiosis [3].…”