Neotrops pombero Grismado and Ramírez, 2013

SPERM TRANSFER FORM (figs. 13, 14): Oval-shaped synspermia (,10 Mm), compris-

ing four spermatozoa that are densely packed (figs. 13, 14A, B). Small, irregular membrane stacks, as well as mitochondria, are present in the periphery (fig. 14C, D). Whereas the cytoplasm is electron lucent within sperm conjugates of the deferent duct (fig. 14C), it further condenses, finally appearing electron dense in sperm conjugates located in the ejaculatory duct (fig. 14 E–F). Sperm are incompletely coiled (fig. 13). A thick (, 250 nm), homogeneous secretion sheath surrounds the sperm transfer forms (fig. 14E).

Spermatozoa (figs. 13, 14): Acrosomal complex: AV conical, long (,9.8 Mm); widened subacrosomal space (fig. 14A), sunken into the prcN (fig. 13). AF originates from the subacrosomal space, extends into the NC, ends clearly before axonemal base. Nucleus: prcN deeply indented at its anterior pole, compact (,11.7 Mm) but irregularly shaped (figs. 13, 14C), chromatin is irregularly condensed (fig. 14C, F). peN small (,5.4 Mm), flattened (fig. 13). NC peripheral (fig. 14C, D). Axoneme: proximal centriole longer than distal centriole. 9+3 microtubular pattern (fig. 14D).

NOTES ON SPERMIOGENESIS (fig. 15): All stages of spermiogenesis are present in the testis. Spermatids of the same developmental stage are arranged in cysts. Early spermatids are characterized by a large AV that is accompanied by a collar of electron-dense secretions and secretion droplets (fig. 15A, A inset, B). Proximal portion of AV is deeply sunken into the anterior pole of the nucleus (figs. 15B, C). The AF originates from the subacrosomal space (fig. 15B). The nucleus is surrounded by a manchette of microtubules. The chromatin appears fibrillar in mid spermatids, although it condenses irregularly (fig. 15B). Late spermatids retain this irregular condensation pattern (fig. 15 C–E). The small implantation fossa is composed of two parts, a spherical portion that contains a small amount of secretions (fig. 15D) and a narrow, tubelike portion where the cen- trioles are located (fig. 15D). The proximal centriole is nearly twice as long as the distal centriole (fig. 15D). A small collar of electron-dense, platelike secretions surrounds the base of the axoneme. At the end of spermiogenesis late spermatids that remained connected via cellular bridges (fig. 15E) start to fuse along their entire length, finally resulting in synspermia.