Mature spermatozoon of Prosorhynchus longisaccatus. (a)–(g) Consecutive cross-sections in region I of the spermatozoon showing external ornamentation of the plasma membrane, cortical microtubules under the plasma membrane, lateral expansion and appearance of both axonemes and spine-like bodies. (h)–(n) Cross-sections in region II of the spermatozoon characterized by the disappearance of the external ornamentation, presence of spine-like bodies, appearance of the mitochondrion and the nucleus, a progressive decrease of the submembranous cortical microtubules and the disorganization of the first axoneme. (o)–(r). Cross-sections in the posterior region of the mature spermatozoon with only one axoneme associated with the mitochondrion, nucleus and some cortical microtubules under the plasma membrane. This region is characterized by the progressive disappearance of the mitochondrion, the second axoneme and then the nucleus. The posterior extremity of this region exhibits only singlets resulting from the disorganization of the second axoneme. Aae1 = anterior extremity of the first axoneme, Aae2 = anterior extremity of the second axoneme, Ax1 = first axoneme, Ax2 = second axoneme, Ax = axoneme, Cm = cortical microtubule, Eo = external ornamentation, Le = lateral expansion, M = mitochondrion, Mi = microtubule, N = Nucleus, Pae1 = posterior extremity of the first axoneme, Pae2 = posterior extremity of the second axoneme, Sb = spine-like body. Scale Bars = 0.2 μm.