Effects on cytokinesis and sperm formation of a b-isochromosome in metaleptea brevicorms adspersa (Acridinae, acrididae)
The behaviour of a large, stable B-isochromosome during male meiosis of Metaleptea brevicornis adspersa Blanch. (Acridinae, Acrididae) was studied in two Argentine populations. The B-chromosome is metacentric and long as the longest members of the standard complement which consists of 23 (22 + X) te...
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00087114_v39_n2_p165_Bidau |
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| Sumario: | The behaviour of a large, stable B-isochromosome during male meiosis of Metaleptea brevicornis adspersa Blanch. (Acridinae, Acrididae) was studied in two Argentine populations. The B-chromosome is metacentric and long as the longest members of the standard complement which consists of 23 (22 + X) telocentric chromosomes in the male. Both arms of the B are consistently completely paired in pachytene and they are positively heteropycnotic along most of their length while their distal ends are isopycnotic. At diplotene, diakinesis and metaphase I the B forms a ring in more than 95% of the analyzed cells and interstitial chiasmata were frequently observed within the euchromatic distal portions. At metaphase I the B-chromosome was oriented at the equator in almost 30% of the cells; this was correlated with a comparable frequency of lagging during anaphase I. The lagging of the B disturbs cell division in such a way that normal telophase separation is impeded with the consequent formation of a restitution diploid nucleus and, simultaneously, the spindle is displaced and an unequal cytokinesis occurs in which a large diploid cell and a small anucleated bud are formed. The abnormal cell division was also observed, though less frequently, during second meiotic division. As a consequence of this process, the production of abnormal spermatids (diploid, tetraploid and microspermatids) in Bcarriers shows a highly significant increase above the normal low level observed in standard males. © 1986 Taylor & Francis Group, LLC. |
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