Silhouettella loricatula ( Roewer, 1942 )

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 : 50

Silhouettella loricatula ( Roewer, 1942)

SPERM TRANSFER FORM ( fig. 37 ): Large, cone-shaped synspermia comprising four sperm. The cytoplasm of the syncytium is heterogeneous and numerous electron-dense plates and droplets, as well as electron-lucent gaps occur ( fig. 37A, B ). The most obvious characteristic is the distinct, irregular chromatin-condensation pattern ( fig. 37B, C ). Numerous platelike membrane stacks are visible in the periphery of the sperm conjugate ( fig. 37D ). A thin homogeneous secretion sheath (, 100 nm) surrounds each sperm conjugate ( fig. 37A, B, D ).

SPERMATOZOA ( fig. 37 ): Acrosomal complex: AV cylindrical. AF originates from the subacrosomal space and extends into the nuclear canal. Nucleus: prcN elongated, characterized by a conspicuous irregular chromatin-condensation pattern ( fig. 37 A– C) and a very small implantation fossa that contains only the two centrioles ( fig. 37B ). peN not visible in mature sperm; NC located in the periphery ( fig. 37C ), but empty for the most part ( fig. 37C ). Axoneme: 9+3 microtubular pattern.

NOTES ON SPERMIOGENESIS ( fig. 38 ): The anterior portion of the prcN is deeply indented and surrounds the AV ( fig. 38A, B ) in addition to a little electron-dense material ( fig. 38B ). Besides the AF the subacrosomal space contains some granular material ( fig. 38B ). The chromatin starts condensation around the nuclear canal ( fig. 38C, D ) before the characteristic chromatin-condensation pattern is formed ( fig. 38 F ). While the nucleus elongates and the chromatin starts to condense, a small dropletlike elongation of the nucleus is formed ( fig. 38E ). This peN probably disintegrates in further development. The implantation fossa is very small and contains only the two centrioles ( fig. 38F ). Neither the centrioles nor the axoneme ( fig. 38F inset) are surrounded by electron-dense material.

Figures

Fig. 37. Characteristics of synspermia of Silhouettella loricatula. A: Numerous sperm conjugates, as well as electron-dense secretions, are visible in the lumen of the deferent ducts. B: Section through sperm conjugates indicates the organization of sperm that are arranged in the center of synspermia, surrounded by heterogeneous cytoplasm. C: The nuclei show a peculiar chromatin-condensation pattern. D: The periphery of the sperm conjugate is composed of small membrane stacks. The entire sperm conjugate is surrounded by a thin secretion sheath.

Fig. 38. Characteristics of spermiogenesis of Silhouettella loricatula. A: The AV is separated from the nucleus by distinct electron-dense plate. B: Higher magnifications reveal little granular material inside the subacrosomal space, in addition to the acrosomal filament. C: The manchette of microtubules and the NC indicate the actual dimensions of the nucleus. D: The NC runs in the periphery of the nucleus and contains the AF. E: While the nucleus elongates a small, droplike peN is formed, which disappears in further development. F: The very small implantation fossa contains only the two centrioles; the axoneme, which possesses the typical microtubular pattern, originates from the distal centriole (inset).