Neoxyphinus termitophilus ( Bristowe, 1938 )

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 : 28-32

Neoxyphinus termitophilus ( Bristowe, 1938)

SPERM TRANSFER FORM ( figs. 18 , 19 ): Large (,25 Mm), oval-shaped synspermia (within the ejaculatory duct) comprising four sperm ( fig. 18 ). Synspermia, located in the deferent ducts, are bottle shaped ( fig. 18 ). The bottleneck contains the acrosomal vacuoles, the short and helically contorted precentriolar parts of the nucleus and the base of the axonemes, as well as postcentriolar elongations of the nucleus, whereas the voluminous bulge is filled with the main parts of axonemes and postcentriolar elongations of nucleus that coil around each other. Numerous mitochondria are located in the periphery of the sperm conjugate ( fig. 19A, B ). A very thin and loosely appearing secretion sheath (, 30 nm), which is produced

in the ejaculatory duct, surrounds the sperm conjugates ( fig. 19 A–C).

SPERMATOZOA ( figs. 18 , 19 ): Acrosomal complex: AV short (,1.2 Mm) and cylindrical

( fig. 18 ). AF originates from the subacrosomal space and extends into the nuclear canal but ends clearly ends before the axonemal base. Nucleus: prcN short (,10.1 Mm), helically contorted with medium-sized implantation fossa that is filled with numerous mitochondria ( fig. 19A ), several spherical secretions, proximal and distal centriole, as well as the base of the Ax. peN extremely elongated (,171.8 Mm), oval in cross sections with distinct projection ( fig. 19A, E ). NC located within a distinct projection, twists around the peN ( figs. 18 , 19A, E ) but is empty for the most part ( fig. 19D ). Axoneme: extremely long (,291.5 Mm); centrioles arranged in tandem position; 9+3 axonemal pattern ( fig. 19B, E ).

NOTES ON SPERMIOGENESIS: Within the testis all stages of spermiogenesis are present, developing spermatids are arranges in cysts. Early spermatids are characterized by a large, oval nucleus that is surrounded by a manchette of microtubules. Mid spermatids are characterized by a small, cylindrical AV ( fig. 20A, B ) that is partly sunken into the anterior pole of the nucleus and accompanied by a small amount of electron-dense material ( fig. 20B ). Further development includes condensation of chromatin that appears fibrillar in mid spermatids ( fig. 20C, D ). Mitochondria are always present within the implantation fossa ( fig. 20D , F–H). Mid- and late spermatids show a characteristic chromatin-condensation pattern in which a small portion remains homogeneously electron lucent ( fig. 20E, E inset). The axoneme is twisted around the postcentriolar elongation, thus both cell components seem to interact ( fig. 20F ). In late spermatids, both centrioles are arranged in tandem position ( fig. 20G ). The implantation fossa is filled with numerous mitochondria ( figs. 20 F–H). The two centrioles and the base of the Ax are surrounded by electron-dense secretion droplets and electron-dense secretion plates ( fig. 20H ). At the end of spermiogenesis four spermatids fuse and form large and voluminous synspermia. During early stages of this sperm conjugation, four mainly individualized spermatids that remained connected to each other via cellular bridges arrange in close association. While the Ax’s, as well as peN’s coil, and form the massive bulge of early bottle-shaped synspermia, the cellular bridges widen posteriorly resulting in a large amount of common cytoplasm. Finally, the common cytoplasm, which contains numerous mitochondria, encases the spermatids secondarily during further differentiation of the sperm conjugate.

Figures

Fig. 18. Surface reconstruction of sperm transfer form of Neoxyphinus termitophilus illustrating the shape and arrangement of all four fused sperm, as well as the arrangement of an individual sperm within the deferent duct. Note the helically contorted prcN and the extremely elongated peN.

Fig. 19. Characteristics of synspermia and mature spermatozoa of Neoxyphinus termitophilus. A: The large oval-shaped sperm conjugate is surrounded by a very thin secretion sheath that is applied in the ejaculatory duct. B: The periphery of the sperm conjugate is composed of numerous mitochondria and small fingerlike constrictions of the membrane of the syncytium. C: These constrictions further deepen and surround the sperm conjugate. D: At the end of spermiogenesis four spermatids arrange closely attached to each other; they do not fuse, but instead cellular bridges (through which spermatids remain connected during spermiogenesis) widen and encase the spermatids, so that each sperm remains surrounded by its own cell membrane. E: The chromatin is irregularly condensed and possesses a distinct electron-lucent patch opposed to the NC, which is, although empty for the most part, partly enlarged.

Fig. 20. Characteristics of spermiogenesis of Neoxyphinus termitophilus. A: Spermatids are characterized by a small AV. The anterior pole of the nucleus is extended at one side and the anterior pole of the AV is attached to the cell membrane. B: Mitochondria are present within the cytoplasm. C: During further development the chromatin starts condensation and appears fibrillar. D: At the posterior portion of the nucleus an IF, which is filled with numerous mitochondria, is formed. E: While the nucleus enormously elongates the characteristic chromatin-condensation pattern (central electron-lucent patch) is developed (inset). F: The axoneme curls around the nucleus. G: The two centrioles are arranged in tandem position. H: Besides the two centrioles and numerous mitochondria, a small amount of electron-dense secretions is present in the IF.