A. Immunofluorescence images of oocytes injected with indicated mMeikin mRNA and fixed at the indicated stage. Kinetochores are stained with mouse CENP-C antibody. Localization was consistent across two experiments. Number of oocytes analyzed: wild-type: Metaphase II – 18, Anaphase II - 21, degron mutant: Metaphase II – 20, Anaphase II - 38. Images of oocytes at the same stage are scaled equivalently. B. Sequence alignment of the non-canonical APC/C D-box motif in Meikin from selected placental mammals. Fully conserved amino acids are indicated in blue. Critical residues changed to alanine in the mutant alleles are indicated. C. Immunofluorescence images of oocytes injected with the indicated mMeikin mRNA and fixed at the indicated stage. Localization was consistent across multiple experiments. The number of oocytes analyzed: wild-type (>5 independent experiments, also see Figure 2E): MI – 58, MII – 69, S381A (two independent experiments): MI – 27, MII – 39. The fraction of oocytes with the displayed meiosis II localization pattern is indicated. Images of meiosis II oocytes expressing the S381A mutant are scaled equivalently. D. Model for differential Meikin activity at distinct stages of meiosis. E. Model for spatial control of Rec8 phosphorylation and cleavage during meiosis I. Created with Biorender.com. Scale bars, 10 μm.