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Haploid karyotype analysis of Chelymorpha variabilis boheman (Coleoptera Chrysomelidae) with microspreading techniques

A. Postiglioni, M. Stoll; N. Brum-Zorrilla

Instituto de Investigaciones Biológicas "Clemente Estable" - IIBCE, Cytogenetics Division, Avda. Italia 3318, Casula de Correo 16012, 11600 Montevideo, Uruguay. Send correspondence to N.B.-Z.

ABSTRACT

The independence of nucleolus and sex chromosomes Xyp in the coleoptera Chelymorpha variabilis Boheman has been demonstrated in a previous paper.
We have now applied microspreading and optical techniques to spermatocytes of this species. Results from TEM techniques are also presented. Haploid karyotypes showed the presence of a nucleolar organizer region in the 5th pachytene bivalent. Sex chromosome axes of X and Y were always found unpaired without any substance surrounding them, quite different from the typical Xyp that has been observed, Postiglioni and Brum-Zorrilla, (Genetica 77: 137-141, 1988). The ease of access to spermatocytes for karyotyping suggests the use of microspreading techniques to study the haploid karyotype of insect chromosomes. Our findings support the non-chiasmatic association of X and Y sex chromosomes.

Keywords: Karyotype; Chelymorpha variabilis; Coleoptera.

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