Fig. 1. Immunofluorescence images of spindle formation in polyspermic zygotes of S. lomentaria. (A,C,E,G) DIC images; (B,D,F,H) merged images of immunolocalization of ß-tubulin (green), centrin (red) and DAPI staining (blue). (A,B) Just before mitosis. Two pairs of centrioles derived from male gametes locate at one side of the nucleus and duplicate there. Therefore, four anti-centrin-positive spots can be observed (arrow in B). (C,D) Migration of four centrosomes to the future mitotic poles. Arrowheads in D show anti-centrin-positive spots. (E,F) Tri-polar spindle is formed and one of the three poles has two centrosomes. Arrowheads in F show four anti-centrin positive spots. (G,H) Tri-polar spindle is formed. One of the four centrosomes is positioned away from the spindle. Arrowheads in H show four anti-centrin-positive spots.