Fig. 3. Immunofluorescence localization of microtubules (green), F-actin (red) and sperm nuclei (blue) in cysts at various stages after elongation. (Column A) Elongated cyst before DNA condensation. There were a number of microtubules around sperm nuclei and microtubule bundles along sperm tails. Nuclei were elongated but not yet condensed (inset). Note that at this stage, no accumulation of actin was seen. (Column B) DNA condensation and F-actin accumulation into an actin cone. Sperm nuclei became thinner (inset in DNA) and actin began to accumulate at the apical side of nuclei. Actin cones were still thin (arrowheads in B-D indicate a single actin cone shown in each inset at higher magnification). (Column C) As the actin cones grew and became thicker, microtubules were excluded from the region but still remained in the cytoplasm. Condensation of sperm nuclei was completed. (Column D) After the onset of actin cone movement, microtubules disappeared. Actin cones became triangular in shape and moved away from the group of sperm nuclei. (E) Actin cones (red) in a cystic bulge in the middle of a cyst. Outline of the individualizing cyst is traced with a white line. The front of the actin cones are wider and the cones are more polarized than at earlier stages. In a non-individualizing cyst (arrowhead), a strong signal of -tubulin staining (green) was observed. However, the individualizing cyst (arrow) had no -tubulin signal. Scale bar: 20 µm.