Spindle length changes dramatically at the meiosis-to-mitosis transition in Ciona and Xenopus, though cell size does not. (A) C. robusta cell diameter and metaphase spindle length (eggs n = 58, zygotes n = 58) measurements. Statistical significance was determined by two-tailed Mann–Whitney tests (**** = P < 0.00005). The line indicates the mean, and the error bars indicate one standard deviation above and below the mean. (B) Image of immunofluorescence of a representative C. robusta zygote in anaphase of the first mitosis. Tubulin (magenta), DNA (cyan). A single z-slice through the center of the spindle is shown. (C)X. laevis cell diameter and metaphase spindle length (eggs n = 10, zygotes n = 10) measurements. Statistical significance determined by two-tailed Mann–Whitney tests (ns = not significant, **** = P < 0.00005). The line indicates the mean and error bars indicate one standard deviation above and below the mean. (D) Higher magnification images of immunofluorescence of spindles from representative X. laevis eggs in metaphase of meiosis II (left panel) and zygotes in metaphase of the first mitosis (right panel) shown in Fig. 1 D. Tubulin (magenta), DNA (cyan). Maximum intensity projection is shown.