Oonops

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 : 38-42

Oonops sp. (Ibiza)

SPERM TRANSFER FORM ( figs. 22 , 23 ): Small (,5 Mm), mainly oval-shaped synsper-

mia ( figs. 22 , 23A ) comprising two sperm ( figs. 22 , 23B ). A distinct, electron-dense vesicular area surrounds all main cell components ( fig. 23 A–C). The cytoplasm appears granular ( fig. 23C, E ). Synspermia are unsheathed; instead, several sperm conjugates cluster in the distal deferent duct, embedded in a distinct secretion matrix ( fig. 23A ).

Spermatozoa ( figs. 22 , 23 ): Acrosomal complex: AV long (,3.9 Mm), cylindrical; narrow subacrosomal space ( fig. 23C ). AF originates from the subacrosomal space, ends in the region of the axonemal base. Nucleus: prcN compact (,4.3 Mm) and tubelike ( fig. 22 ) with a distinct crest, on which the nuclear canal is running ( figs. 22 , 23D, E ). The implantation fossa is small but wide ( fig. 23 D, E ). Besides a little granular material, presumably glycogen ( fig. 23D ), the implantation fossa contains the two centrioles and the base of the Ax ( fig. 23E ). peN nearly as long as prcN (,2.9 Mm) and flattened ( figs. 23 , 24E ). NC located in the periphery, on a distinct crest ( fig. 23E ). Axoneme: long

(,23.4 Mm), 9+3 microtubular pattern ( fig. 23E inset).

NOTES ON SPERMIOGENESIS ( fig. 24 ): Within the testis all stages of spermiogenesis

are present; spermatids are arranged in cysts of the same developmental stage. Early spermatids are characterized by a large, mainly spherical nucleus that is surrounded by a manchette of microtubules ( fig. 24A ), and a developing acrosomal complex, which is attached to the anterior pole of the nucleus ( fig. 24A ). During further differentiation, the acrosomal vacuole sinks into the nucleus ( fig. 24B, C ). Simultaneously, the two centrioles migrate toward the posterior pole of the nucleus, consequently forming an implantation fossa ( fig. 24B ). The posterior portion of nucleus is constricted, resulting in a small neck. Chromatin condensation occurs heterogeneously and shows a specific pattern, in which a distinct crest of dense chromatin is separated from the remaining, tubelike condensing chromatin of the nucleus ( fig. 24B ). The NC that contains the AF is located in the periphery of this crest ( fig. 24B, D ). At the end of spermiogenesis, the Ax is retracted and coils within the cell membrane ( fig. 24E ). At the same time, several electron-dense vesicles fuse, initiating formation of a distinct vesicular area that surrounds all main sperm cell components ( fig. 24E, F ). Finally, two spermatids that are still connected via cellular bridges fuse, forming synspermia ( fig. 24E, F ).

Figures

Fig. 22. Surface reconstruction of sperm transfer form of Oonops sp. (Ibiza) illustrating the shape and arrangement of two fused sperm, as well as the arrangement of an individual sperm. Note the very long AV, which is nearly as long as the prcN and the small peN.

Fig. 23. Characteristics of synspermia of Oonops sp. (Ibiza). A: Sperm conjugates, which are composed of two sperm, arrange in cluster. B: Synspermia are not provided with a secretion sheath, but show a distinct electron-dense vesicular area. C: The condensed chromatin appears fibrillar, distinct electronlucent stalks appear, and the cytoplasm appears granular in sperm conjugates. D: The NC is located on a distinct projection, running in the periphery of the nucleus; note mitochondria within the cytoplasm. E: The base of the axoneme, with a typical 9+3 microtubular pattern (inset), is associated with a little electron-dense material. F: Note a small amount of glycogen is present in the IF, as well as within the cytoplasm of the sperm conjugate. A thin ribbon originating from the vesicular area is located in the periphery of the sperm conjugate underneath the membrane of syncytium.

Fig. 24. Characteristics of spermiogenesis of Oonops sp. (Ibiza). A: The small developing AV is attached to the cell membrane anteriorly (magnification in inset); the nucleus is surrounded by a manchette of microtubules. B: The chromatin condenses irregularly and appears fibrillar in midspermatids. C: The elongated AV is surrounded by electron-dense material (arrow) at the anterior pole of the nucleus. D: The AF extends into the NC that is located on a distinct projection in the periphery of the nucleus. E: At the end of spermiogenesis, the main cell components coil within the cell membrane, while the spermatids remain connected with each other via cellular bridges. F: Finally, two spermatids fuse, forming a mainly spherical sperm conjugate.