The relative positions of condensed chromosomes are maintained between divisions in the epidermis of Calpodes ethlius

Abstract

The larval epidermis of Calpodes ethlius (Lepidoptera, Hesperiidae) is a syncytium of doublets where sibling cells are twins that remain connected by residual midbodies between mitoses. Twins resemble one another more than their other neighbours in such structural features as the shape and number of nucleolar particles and the number of actin bundles. We have now found that they also resemble one another in the position of the condensed chromosomes that occur in female cells. Female lepidopteran cells contain one or more particles of condensed chromatin, depending on their ploidy. In the epidermis, nuclei with two condensed chromosomes are found in pairs and are separated by the same distances. However, clones of cells with multiple condensed chromosomes are not all alike, suggesting that chromosomes are repositioned at mitosis. Separation distances between chromosomes remain the same between but not through cell divisions, suggesting that determinants for nuclear structure are conserved through interphase and relaxed at mitosis. Although the condensed chromosomes of sibling nuclei resemble one another in their separation, they differ in their orientation, as would be expected if whole nuclei rotate in the plane of the epithelium.