Nucleolus organizing regions and semi-persistent nucleolus during meiosis in Spartocera fusca (Thunberg) (Coreidae, Heteroptera).
The Coreidae are cytogenetically characterized by possessing holokinetic chromosomes and a pre-reductional type of meiosis. The modal diploid chromosome number of the family is 21, with a pair of m chromosomes and an XO/XX sex chromosome determining system. Spartocera fusca presents 2n=23/24=20+2m+XO/20+2m+XX (male/female). Meiosis follows the general pattern described for heteropterans, with a diffuse stage after pachytene and a particular chromosome arrangement at both metaphase plates. S. fusca presents some cytogenetic peculiarities: the X chromosome shows a secondary constriction in a medial position, which is not a nucleolus organizing region. It has been revealed by in situ hybridization with a rDNA probe that the NOR is localized at the telomeric region of one autosomal pair. Furthermore, during the meiosis of three specimens of S. fusca a semi-persistent nucleolus was detected from early meiotic prophase until telophase II; the presence of this semi-persistent nucleolus together with the long diffuse stage detected in the specimens suggest that a continuous biosynthetic activity is required for spermiogenesis. These observations could be related to differences in the environmental, and therefore, physiological conditions of the analyzed individuals.
Cattani
M V
MV
Laboratorio de Citogenética y Evolución, Depto. de Ecología, Genética y Evolución, Fac. de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina. vcattani@fibertel.com.ar
Papeschi
A G
AG
D000818:Animals; D002466:Cell Nucleolus / Q000235:genetics*; D015342:DNA Probes; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D005260:Female; D020062:Heteroptera / Q000166:cytology / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D008540:Meiosis / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000502:physiology*; D012730:Sex Chromosomes / Q000235:genetics*
D015342:DNA Probes; D004275:DNA, Ribosomal