Breakage of chromosomes was induced by X-rays in adult and nymphal males of Euschistus servus, E. tristigmus and Solubea pugnax (Pentatomidae; Hemiptera-Heteroptera).
The diffuse nature of the kinetochore is demonstrated by the ability of chromosome fragments to perpetuate themselves mitotically through many cell generations of spermatogonia.
Free fragments, when not immobilized by the effects of radiation, are also capable of meiotic mitosis. A holokinetic, rather than a telomeric, nature is thus demonstrated for the meiotic restriction of kinetochore activity to chromosome ends, normal for Heteroptera and certain other Hemiptera.
Simple fragmentation as a factor in the evolution of compound sex chromosomes is supported by the observation that fragments of the X chromosome co-orient with the Y in a typical “touch and go” pairing.
The results are discussed with relation to problems of kinetochore structure and mitosis.
Unable to display preview. Download preview PDF.