Meiosis and the Neo-XY system of Dichroplus vittatus (Melanoplinae, Acrididae): a comparison between sexes.

摘要: The origin of neo-XY sex systems in Acrididae is usually explained through an X-autosome centric fusion, and the behaviour neo-sex chromosomes has been solely studied males. In this paper we analysed male female Dichroplus vittatus. karyotype comprises 2n = 20 including 9 pairs autosomes a chromosome pair that includes large metacentric neo-X small telocentric neo-Y. We compared meiotic bivalent between both sexes. Mean cell autosomal chiasma frequency was low sexes slightly but significantly higher males than females. Chiasma females increased when sex-bivalent included. distribution basically distal Behaviour complex as priori suggested by its structure, which mitosis meiosis diploid polyploid cells. During meiosis, orientation highly irregular; only 21% metaphase I spermatocytes show standard orientation. rest cells, alternate or simultaneous activity extra kinetochore end short arm (XL) neo-X, determined unusual MI orientations high non-disjunction lagging sex-chromosomes. females, neo-XX had more regular showed 17% asynapsis XL which, those cases orientated ends towards opposite spindle poles suggesting, again, second kinetochore. dicentric nature unstable neo-chromosomes D. vittatus suggest recent determination mechanism, with presumable adaptive advantages could compensate their potential negative heterosis. Our observations system tandem fusion two original X-chromosomes followed another megameric further pericentric inversion neo-X. remaining homolog resulted neo-Y chromosome.