Fig. 5

The morphologies of the Pacific oyster Crassostrea gigas sperm by scanning electron microscopy. A The sperm have a two-level acrosome with an apical knob and a wide mitochondrial area; B the sperm have a two-level acrosome with an apical knob and a narrow mitochondrial area; C the sperm have a two-level acrosome without an apical knob and with a wide mitochondrial area; D the sperm have a two-level acrosome without an apical knob and with a narrow mitochondrial area; E the sperm have a platelet-like acrosome; F the sperm have a non-central platelet-like acrosome. A–F Respectively correspond to 1–6 for diagrams 6a–d. Arrows show the apical knob; a acrosome; n nucleus; m mitochondrial area; f flagellum. Scale bar—1 µm