Figure 4. Immunolocalization of Es-Caspase 8 during spermatogenesis in E. sinensis. Red: Es-Caspase 8, Green: Tubulin, Blue: Nucleus. N: nucleus, PG: preacrosomal granule, PV: proacrosomal vesicle, AT: acrosome tube, AC: acrosome cap, AV: acrosome vesicle, FL: fibrous layer, ML: middle layer, LS: lamellar structure, MC: membrane complex, RA: radical arm, NC: nuclear cap, MT: mitochondria. (A1-A4) spermatogonia, (B1-B4) spermatocyte, (C1-C4) stage I spermatid, (D1-D4) stage II spermatid, (E1-E4) stage III spermatid, (F1-F4) mature sperm. Weak Es-Caspase 8 are expressed in the cytoplasm of spermatogonia. In spermatocyte, Es-Caspase 8 are enhanced, distributing in the cytoplasm. Signals transfer in one pole of cytoplasm in the next stage. In stage II and III spermatids, the upper half part of proacrosome present Es-Caspase 8 distribution. In mature sperm, Es-Caspase 8 was distributed in mature AC. Bars=20 um.