Neotrops pombero Grismado and Ramírez, 2013

Lipke, Elisabeth & Michalik, Peter, 2015, Evolutionary Morphology Of The Primary Male Reproductive System And Spermatozoa Of Goblin Spiders (Oonopidae; Araneae), Bulletin of the American Museum of Natural History 2015 (396), pp. 1-72 : 15-17

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.

Figures

Fig. 13. Surface reconstruction of sperm transfer form of Neotrops pombero illustrating the shape and arrangement of all four fused sperm, as well as the arrangement of an individual sperm. Note the very long AV, which is nearly as long as the prcN. Axonemes are not shown in this reconstruction.

Fig. 14. Characteristics of synspermia and spermatozoa of Neotrops pombero. A: Within the proximal portion of the deferent duct, synspermia are irregularly formed and embedded in a dense matrix composed of longish, electron-dense secretions, a secretion sheath surrounds the sperm conjugates. B: In contrast, synspermia in the lumen of the ejaculatory duct are oval, the cytoplasm is further condensed and appears electron dense. C: The four fused sperm show a characteristic, irregular chromatin-condensation pattern. The condensed chromatin appears fibrillar and possesses numerous electron-lucent streaks. D: Numerous membrane stacks, as well as a few mitochondria are visible in the periphery of the sperm conjugate. E: The NC in the periphery of the nucleus is located on a distinct projection. F: The posterior portion of the AV is deeply sunken into the anterior pole of the nucleus and thus partly surrounded by the latter.

Fig. 15. Characteristics of spermiogenesis of Neotrops pombero. A: The posterior portion of AV is already sunken into the anterior pole of the nucleus in early spermatids; the AF is thin, the subacrosomal space is widened (inset). Note distinct electron-dense spots (arrow) that occur at the anterior pole of the nucleus. B: The chromatin appears fibrillar and starts condensation in the center of the nucleus. C: The elongating AV is accompanied by electron-dense secretions (magnified in inset). D: The proximal centriole is enlarged and nearly twice as long as the distal centriole; the base of the axoneme is surrounded by few electron-dense secretions (inset). E: At the end of spermiogenesis, the main sperm cell components coil within the cell membrane, while the spermatids are still connected with each other via cellular bridges (asterisk). Finally four spermatids fuse and form oval synspermia. Note mitochondria within the cytoplasm.