part of actomyosin contractile ring prospore contractile ring A contractile ring, i.e. a cytoskeletal structure composed of actin filaments and myosin, that forms beneath the plasma membrane of the prospore envelope in meiotic cells in preparation for completing cytokinesis. actomyosin ring meiotic contractile ring GO:0032157 cellular_component cytokinetic ring ascospore-type prospore meiotic actomyosin contractile ring