Non-relationship between nucleolus and sex chromosome system XypinChelymorpha variabilisboheman (Coleoptera: Chrysomelidae)
✍ Scribed by A. Postiglloni; N. Brum-Zorrilla
- Book ID
- 104625023
- Publisher
- Springer Netherlands
- Year
- 1988
- Tongue
- English
- Weight
- 381 KB
- Volume
- 77
- Category
- Article
- ISSN
- 0016-6707
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✦ Synopsis
Nucleolar-organizer region, nucleolus and mode of association of the sex bivalent were analyzed in spermatocytes of Chelymorpha variabilis Boheman. This species (2n = 10II + Xyp) shows the typical sex chromosome system of the group Pol~yqghaga. The results of silver staining techniques showed the nucleolar organizer region localized in a subterminal position of an autosomal bivalent. During meiotic prophase the nucleolus was distinguished with the silver staining and acridine orange fluorescence technique up to diakinesis. The independence of nucleolus and sex bivalent Xyp during meiosis is demonstrated. The positively silver staining but negatively orange-red material found within the parachute could be involved in the regular co-orientation of both sex chromosomes. After a longer hypotonic treatment, sex bivalents were observed elongated and paired only at one end during the pachytene stage. Along these sex chromosomes, C-bands showed positive blocks located in the pericentromeric and telomeric regions. Heterochromatic association of both sex chromosomes was suggested.