Patterns of spindle movements among various nematode species.

<p>(A) (Left) Schematic representations of an embryo from the meeting of the pronuclei to the first cell division. Microtubules are shown in green and chromosomes in blue. Mechanical forces pulling on astral microtubules are responsible for nuclei and spindle movements and are shown as black arrows. (Right) DIC still images of embryos (at stages corresponding to the schematics) from four <i>Caenorhabditis</i> species (<i>C</i>. <i>elegans</i> and three species from the non-<i>Elegans</i> group) and <i>Oscheius tipulae</i> from another genera. Anterior and posterior sides are left and right, respectively. The white dotted line represents the middle of the cell. Centrosomes (center in blue and contour in red) were detected by an automated program for all these species except for <i>C</i>. <i>virilis</i>, where the centrosomes have been tracked manually (shown as blue dots). Scale bar: 10 μm. (B, C) Time course of displacement of the spindle center along the antero/posterior axis of the cell, relative to the center of the cell (B) and transverse oscillations of anterior (green) and posterior (red) centrosomes relative to the cell equator (C) for the five species shown above. <i>y</i> and <i>x</i> axes are measured in μm and s, respectively. T = 0s corresponds to the onset of nuclear envelope breakdown. Corresponding numerical values are provided in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2005099#pbio.2005099.s010" target="_blank">S3 Table</a>. DIC, differential interference contrast.