Mechanisms of sperm release from the receptaculum seminis of Schistocerca vaga Scudder (Orthoptera: Acrididae)

Release of spermatozoa from the receptaculum seminis of Schistocerca vaga was studied by means of electrical and mechanical stimulation. Electrical stimulation of the receptaculum nerve, or the ductus aperture nerve, leads to release of spermatozoa from the receptaculum seminis, provided the spermathecal innervation is intact. Mechanical stimulation of the ductus aperture in the genital chamber also leads to sperm release, provided the neural loop, ductus aperture/terminal abdominal ganglion/receptaculum seminis, has not been interrupted at any point. Ten somata in the terminal abdominal ganglion, including 6 dorsal unpaired medial (DUM) neurons, innervate the receptaculum seminis; some of these somata may be neurosecretory. Approximately 80 presumed sensory axons run from the ductus aperture to the same ganglion. On the basis of these neuroanatomical data and the results of electrical and mechanical stimulation, a schema of how the release mechanisms operate in S. vaga is proposed.     

Ultrastructure of receptaculum seminis in Haemaphysalis longicornis (Acari: Ixodidae) in relation to inserted endospermatophore

The receptaculum seminis, opening into the female genital tract, is found only in the metastriate ixodid ticks. An endospermatophore that has been inserted into the female genital aperture at copulation is first stored in the receptaculum seminis, where spermiogenesis is completed before the sperm ascend the oviducts. The receptaculum seminis consists of a simple cuticularized epithelium. Epithelial cells in sexually matured females develop during feeding and become active in secretion. Secretions discharged from epithelial cells are released into the lumen of this organ through the cuticle and may act on the wall of the inserted endospermatophore. The fact that resumption of spermiogenesis (spermateleosis) has already occurred before destruction of the endospermatophore just after copulation suggests that secretions from epithelial cells of the receptaculum seminis are not the trigger of spermateleosis, but a destructive agent of the endospermatophore wall. J Morphol 231:143–147, 1997. © 1997 Wiley-Liss, Inc.     

Spermiogenesis and sperm ultrastructure of Cyathocephalus truncatus (Pallas, 1781) Kessler, 1868 (Cestoda: Spathebothriidea)

Spermiogenesis and sperm ultrastructure of adult Cyathocephalus truncatus, a member of presumably basal group of "true" cestodes (Eucestoda), have been examined for the first time by using transmission electron microscopy. The process of sperm formation corresponds in basic pattern to that of the Pseudophyllidea. In addition, the 2 pairs of electron-dense attachment zones are present in median cytoplasmic process of C. truncatus. However, mature spermatozoa of C. truncatus differ significantly from those of the pseudophyllideans, especially in the morphology of the proximal and distal spermatozoon extremities. The proximal extremity of the mature spermatozoon lacks a crested body, which is present in more derived cestodes and some pseudophyllideans. The distal end of the mature spermatozoa exhibits different morphology in the gametes from testes and those from receptaculum seminis. New for the Eucestoda is a finding that a lateral cytoplasmic extension creates the distal end of the spermatozoa from testes, resembling sperm of some Monogenea and Digenea. In contrast, the distal extremity of the spermatozoa from receptaculum seminis contains only a nucleus. Despite the above-mentioned peculiarities, the ultrastructural data on sperm/spermiogenesis suggest close relationships of the Spathebothriidea and Pseudophyllidea.     

Histochemical studies on Raillietina (Raillietina) johri (Cestoda: Davaineidae). I. Nonspecific and specific phosphatases.

Certain phosphatases have been localized by histochemical techniques in various tissues of a pigeon cestode, Raillietina (Raillietina) johri. Acid phosphatase (AcPase), alkaline phosphatase (AlPase) and adenosine triphosphatase (ATPase) were present in almost all structures: tegument; subtegumental muscles; subtegumental cells; excretory canal; testes; sperm ductules; vas deferens; cirrus sac; cirrus; ovary; receptaculum seminis; vagina; vitelline gland cells; oocytes; uterus; embryonated eggs. AlPase was absent in parenchyma, spermatocytes, spermatids and spermatozoa. AlPase activity was more intense in the tegument of mature gravid proglottides. AcPase and ATPase were visualized in various stages of spermatogenesis of the parasite. ATPase activity was also observed in chromosomes. 5'-nucleotidase (AMPase) activity was restricted to embryonated eggs only. Functional significance of these phosphatases is discussed.     

The morphology and ultrastructure of the female reproductive ducts in the metacercaria and adult of Cryptocotyle lingua (Creplin) (Digenea:Heterophyida)

Encysted metacercariae of C. lingua require 38 days in the fish second intermediate host before they are infective to the bird definitive host. Morphogenesis of the metacercaria is arrested shortly after 38 days. The ovary and testes are recognizable at 10 days. By 38 days the lumen of the oviduct is apparent and cilia form on the epithelial lining. The receptaculum seminis remains rudimentary. The cells of the uterine primordium are vacuolated but no lumen is present. Laurer's canal, vitelline glands, and Mehlis's glands are not recognizable. Morphogenesis is resumed in the bird intestine. During day 1 the oviduct and receptaculum seminis complete their development; Laurer's canal and the uterine lumen are formed. During day 2 the cilia in the female ducts become motile and the vitelline and Mehlis's glands are present. Fertilization occurs on day 2 to day 3 and eggs arrive in the uterus on day 3.     

Anatomy and ultrastructure of the reproductive systems ofAcarus siro (Acari: Acaridae)

Anatomy and ultrastructure of the female and male reproductive system inAcarus siro L. were investigated by light and electron microscopy. The female system consists of paired ovaries of nutrimentary type in which oogonia and oocytes are connected by bridges with a large central cell. The oviducts empty into the uterus, which passes into preoviporal duct lined bycuticle, and opening as a longitudinal slit (oviporus). An elongated accessory gland composed of one type of secretory cell is located along each oviduct. The copulatory opening occurs at the posterior margin of the body and leads, via the inseminatory canal, to the receptaculum seminis, consisting of the basal and saccular part. Both inseminatory canal and basal part of receptaculum seminis are lined by cuticle, whereas the wall of the sac is formed by cells covered only by long, numerous microvilli. The basal part of the receptaculum seminis joins the ovaries via two lumenless transitory cones.The male reproductive system contains paired testes, in which spermatogonia tightly surround the central cell. The proximal part of the paired vasa deferentia serves as a sperm reservoir, while the distal one has a glandular character. An unpaired, cuticle-lined ejaculatory duct opens into the apex of the aedeagus. The single accessory gland is located asymmetrically at the level of, or slightly posterior to, coxae IV.The structure of the genital papillae, which are topographically related to the genital opening in both sexes, is also briefly described.     

Tyrrhenia blennii g.n. sp. n. (Hemiurata : Halipegidae Poche, 1925) parasite of Blennius gattorugine and Blennius sanguinolentus]

Trematodes recovered from Blennius gattorugine and Blennius sanguinolentus from the Gulf of Gaeta, Italy, are described and figured as Tyrrhenia blennii g.n. sp.n. The new genus differs from other members of the Arnolinae Skrjabin and Guschanskaja, 1958 (Halipegidae Poche, 1925) chiefly in having acetabulum equatorial, receptaculum seminis uterinum present and eggs without filaments. The diagnosis of the new genus Tyrrhenia and a key to genera of Arnolinae are given.     

Seminal receptacula in gravid and virgin female Peripatus (Macroperipatus) acacioi Marcus and Marcus (Onychophora,Peripatidae)

The ovoid seminal receptacula in Peripatus acacioi are located at the junctions of the short paired oviducts with the two horns of the uterus. Associated with each is a tubular funnel that opens into the haemocoel. In P. acacioi, spermatozoa may be stored in the seminal receptacula for several years (Campiglia and Walker '95, J. Morphol. 224:179–198). Observations of the structure of the seminal receptaculum using transmission electron microscopy (TEM) show that there are numerous tracheae within its wall indicating a good oxygen supply. The ultrastructure of the epithelium lining the seminal receptaculum indicates that these cells secrete the material that forms the luminal matrix that surrounds and provides nutrition for the stored spermatozoa. The ducts that interconnect the ovary, seminal receptaculum, funnel, and uterus are all packed with cilia. The structure of the seminal receptaculum and associated parts in the mature virgin female is identical to that of the gravid female, but the luminal matrix does not contain any spermatozoa. J. Morphol. 237:127–136, 1998. © 1998 Wiley-Liss, Inc.     

Ultrastructural investigations of the female genital system of Epiperipatus biolleyi ( Bouvier 1902) (Onychophora,Peripatidae)

Brockmann, C., Mummert, R., Ruhberg, H. and Storch, V. 1999. Ultrastructural investigations of the female genital system of Epiperipatus biolleyi (Bouvier 1902) (Onychophora, Peripatidae). — Acta Zoologica (Stockholm) 80: 339–349. The female genital system of the neotropical peripatid Epiperipatus biolleyi was examined using transmission and scanning electron microscopy. Special attention is given to the two accessory organs of the paired oviducts: the receptacula seminis and the ovarian funnels (Ovarialtrichter). The latter occur only in the Peripatidae, whereas receptacula seminis may also be present in the Peripatopsidae, the only other family in the Onychophora. The ovarian funnels of E. biolleyi are thin-walled and closed from the haemocoel. This trait has also been reported from Epiperipatus trinidadensis, Macroperipatus torquatus, and Eoperipatus weldoni, whereas other peripatids have ovarian funnels which have been reported to open into the haemocoel. The occurrence of artificially opened ovarian funnels, caused by tissue rupture during specimen preparation, is discussed. The presence of spermatozoa both in the receptaculum seminis and in parts of the uterus of the female examined in this study supports the hypothesis that in E. biolleyi insemination of juvenile females occurs directly via the genital opening. The female contained one unstalked cleavage embryo in each uterus horn. Two features of the uterus were found to be unique to E. biolleyi: (1) a second cell layer overlying the uterine epithelium with a pronounced secretory activity (2) embryos are enclosed in a noncellular coat interspersed with numerous transport vesicles.     

Evidence of a neural loop involved in controlling spermathecal contractions in Locusta migratoria

The control of spermathecal contractions in Locusta migratoria via a neural loop was demonstrated using mechanical stimulation and electrophysiological recordings. Extracellular electrophysiological recordings from the receptaculum seminis nerve (N2B2), which innervates the spermathecal sac, were conducted during mechanical stimulation of the genital chamber sensory cells. Activation of the genital chamber sensory cells, using a glass probe approximating the shape and size of an egg, was found to increase the action potential frequency and initiate bursts of action potentials if a tonic frequency of action potentials was present prior to stimulation. If the motor pattern initially consisted of bursts of action potentials, then mechanical stimulation of the genital chamber sensory cells resulted in an increase in firing frequency, in most preparations, with the bursting remaining. Removal of the probe from the genital chamber always returned the motor activity to that noted prior to sensory cell stimulation. Simultaneous electrophysiological recordings from both the left and right receptaculum seminis nerves (N2B2) revealed that the bursts of action potentials were coordinated, although individual action potentials were not coupled one to one. Activation of the genital chamber sensory cells also resulted in increases in spermathecal contraction frequency, an effect which was coordinated with the changes in motor activity. It is proposed that an egg in the genital chamber activates the sensory cells resulting in increases in spermathecal contraction frequency and the subsequent release of spermatozoa onto the micropyle of the egg for fertilization.     

The spermatozoa and eggs of the cardinal fish

The gametes of the cardinal fish Apogon imberbis had the following characteristic: the semen contained both biflagellate (  c . 20% in the investigated samples) and monoflagellate (  c . 80%) spermatozoa. The spermatozoa were acrosomless, had an ovoid head, and a cylindrical midpiece. The midpiece contained a high number of mitochondria (seven–10). The distal centriole was fastened to the nucleus via electron-dense material. The proximal centriole was completely reduced. The eggs were spherical, had a smooth surface and one micropyle consisting of the micropylar channel, the vestibulum and a ring-like convulsion bordering the vestibulum. The zona radiata was formed out of four layers which could be distinguished by their fine structural and histochemical features. It was only c . 1·5 µm thick and therefore much thinner than in other marine teleosts. The internal organization of the eggs (homogenous protein yolk containing cortical granules and lipid droplets) as well as the qualitative and quantitative biochemical composition of proteins, lipids and carbohydrates was similar to that of the pelagic eggs of other marine species.     

Centriole behavior in chloramphenicol-treated eggs of the sand dollar,Dendraster excentricus

Summary This electron microscope study was undertaken to test the prediction made from an indirect assay method for mitotic centers (centrioles), that chloramphenicol inhibits centriole replication during first cleavage division in the eggs of the sand dollar,Dendraster excentricus. Extensive serial sectioning through both untreated and chloramphenicol-treated eggs, coupled with thorough examination of these sections, has demonstrated that 57% of the untreated eggs and 14% of the chloramphenicol-treated eggs contained paired centrioles at a time when centriole pairs normally exist. This study thus gives direct evidence that chloramphenicol inhibits centriole replication.     

Further studies on the morphology of the Triviidae (Gastropoda: Prosobranchia) with emphasis on species from southern Africa

Aspects of the morphology of II species of Triviidae are described, including the living animal, shell, radula, mantle complex, central nervous system and reproductive system. Interspecific differences in radular morphology are important in distinguishing closely allied species. Trivia aperta, T. costata and T. verhoeft are protandric hermaphrodites while T. caluariola, T. neglccta, T. pellucidula, T. rubra, T. solandri and T. suavis are gonochoric. The elaboration of the receptaculum seminis varies between species. In T. aperta, T. calvariola, T. neglecta and T. who& the receptaculum is undivided while in T. costafa, T. pellucidula, T. solandri and T. suavis there are two or more lobes of the receptaculum.     

The neural control of spermathecal contractions in the locust,Locusta migratoria

The innervation of the spermatheca and demonstration of neural control of spermathecal contractions in Locusta migratoria was illustrated using anterograde and retrograde fills, combined with electrophysiological stimulation and recording. The anterior portion of the spermatheca receives innervation via the receptaculum seminis nerve (N2B2) from two large ventral neurons and one dorsal neuron. All were bilaterally paired and situated in the VIIIth abdominal ganglion. Three ventral bilaterally paired neurons situated in the VIIIth abdominal ganglion also provide innervation to the posterior portion of the spermatheca via the ductus seminalis aperture nerve (N2B3). Six DUM neurons, located in the VIIIth abdominal ganglion, in addition to two centroposteriorly situated DUM neurons in the VIIth abdominal ganglion, are also associated with these two nerves. N2B4 also provides innervation to the posterior portion of the spermatheca. N2B6b is associated with sensory cells identified in the anterior lateral regions of the genital chamber. The spermatheca contracts spontaneously, with peristaltic contractions beginning at the spermathecal sac and continuing along the length of the spermathecal duct. However electrical stimulation of the ventral ovipositor nerve (VON or N2B), receptaculum seminis nerve (N2B2) and the ductus seminalis aperture nerve (N2B3) indicates that contractions are also under neural control. In particular contractions of the spermathecal sac, coil duct and anterior straight duct are initiated via motor projections from the receptaculum seminis nerve (N2B2) and posterior straight duct contractions are controlled by motor input from the ductus seminalis aperture nerve (N2B3). The results suggest that spermathecal contractions of the anterior and posterior portions of the spermatheca are under separate neural control.     

Sperm ultrastructure in the inseminating Macropsobrycon uruguayanae (Teleostei: Characidae: Cheirodontinae)

Macropsobrycon uruguayanae is a small, inseminating characid (tetra) of the tribe Compsurini. Although spermatozoa can be found within the ovarian cavity close to oocytes, the exact moment of fertilization has not yet been determined. Spermatozoa have moderately elongate nuclei with electron-dense chromatin. During spermiogenesis, nuclear rotation takes place. Elongate mitochondria with lamellar cristae are found posterior to the nucleus. Centrioles are parallel to one another with the proximal centriole slightly anterior to the longer distal one. The anterior tip of the proximal centriole is located within a shallow nuclear fossa. Electron-dense spurs are associated within the anterior and posterior ends of the distal centriole. Striated centriolar rootlets radiate both anteriorly and posteriorly from the distal centriole. Nine longitudinal accessory microtubules surround the axoneme in the proximal flagellum. The flagellum has a typical 9 + 2 axoneme with no intratubular differentiation. Atypical spermatozoa are also found in the testicular lumen. These cells resemble spermatozoa in most aspects, except that their nuclei are variable in shape, with the granular chromatin less electron-dense than that seen in spermatozoa. The origin and function of these cells could not be determined. The specializations seen in the spermatozoa are discussed as possible adaptations related to the habit of insemination.     

Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implications

The spermatozoon of Apus apus is typical of non‐passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non‐passerines. All non‐passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non‐passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA–DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae.     

Ultrastructure of the reproductive system of the house dust mitesDermatophagoides farinae andD. pteronyssinus (Acari,Pyroglyphidae) with remarks on spermatogenesis and oogenesis

Several parts of the reproductive system of both sexes ofDermatophagoides farinae andD. pteronyssinus are investigated and compared by light-, scanning electron-, and transmission electron microscopy. New techniques have been employed for scanning of the internal structures of these mites. The male reproductive system consists of unpaired testis, paired vasa deferentia, an accessory gland, ejaculatory duct, and copulatory organ. The female reproductive system consists of bursa copulatrix, ductus bursae, receptaculum seminis, paired ducti receptaculi, ovaries, oviducts, one chorion gland, ovipositor, and oviporus. Testis as well as ovaries are characterized by syncytia of nutritional function. The specifics of spermatogenesis are discussed in connection with sperm transfer. Similarities between the construction of the ovaries and oogenesis in astigmatic mites and telotrophic meroistic ovaries in insects are discussed.     

On the Anatomy and Systematic Position of the Mathildidae (Mollusca, Allogastropoda)

The anatomy of two mathildid species, Opimilda maoria Powell, 1940 and Gegania valkyrie Powell, 1971 has been investigated using serial sections. The mathildid anatomy strongly resembles that of the Architectonicidae, and therefore both families are included in the superfamily Architectonicoidea. The buccal system of Gegania valkyrie is the most primitive of all Allogastropoda (Architectonicoidea and Pyramidelloidea) so far investigated. Reproductive features within with Architectonicoidea vary. Certain species ( Gegania valkyrie ) are hermaphrodites, whilst others ( Opimilda maoria ) appear to be gonochorists; in these species males also possess a (sperm-filled) receptaculum seminis. Similar genital and reproductive features are found in the prosobranch relict species Campanile symbolicum Iredale, 1917, the systematic position of which is discussed briefly.     

Ultrastructural modifications of the glandular epithelium of the receptaculum seminis in Thermobia domestica (Insecta: Thysanura) during the moulting period

Summary The wall of the receptaculum seminis of Thermobia domestica is composed of numerous glandular units, each with four enveloping cells (denoted 1 to 4) separated by ordinary epithelial cells and associated with a cuticular apparatus. During the moulting periods, which continue to occur in the adult stage, these cells undergo a series of transformations. Just before apolysis there is a dedifferentiation of numerous cytoplasmic organelles, but no mitosis has been observed. When the intima lifts off, the apical system of each glandular unit, i.e. the distal parts of the C2 and C3 cells surrounding the end apparatus, is also eliminated. Then at the apex of each glandular unit, a new ductule is formed in the cavity of which a long ciliary process grows up from cell C1. Finally comes the phase of cuticle formation, i.e., epicuticle for the ductules, epi-and endocuticle for the intima lining the central cavity of the receptaculum. Various cell types participate in secretion of cuticle, the ciliary cells (C1) being responsible for the formation of the porous end apparatus. At ecdysis almost all of the new intima has been secreted and the apical systems are once more differentiated. These transformations are compared with those recently described in other exocrine glands of arthropods, e.g., tegumentary glands and accessory glands of the genital ducts.     

The transformation of male sex cells of Tetranychus urticae K. (Acari,Tetranychidae) during passage from the testis to the oocytes: an electron microscopic study

The fine structure of the spermatozoon of Tetranychus urticae is described during passage from the testis to the site of insemination in the ovary. The male sex cells differentiate from a cytoplasmic mass which is characterised by nuclei bearing tubule-like structures. Infoldings appear in peripheral membrane of the germ cells at the beginning of spermiogenesis, chromatin condenses, and the nuclear membrane is reduced. The spermatozoon is surrounded by a double membrane: the inner one is the sperm membrane and the outer one is of somatic origin. The sperm reach the glanular region of the testis where they are transformed into amoeboid cell and are next collected in the seminal vesicle.

After copulation, the sperm can be observed in the lumen of the receptaculum seminis of the female from which they soon enter the epithelial cells. Still surrounded by a double membrane, the sperm, which are now packed in clusters, develop microtubules immediately beneath the inner membrane and enlarge by decondensation of chromatin and by infiltration of cytoplasmic material. Insemination takes place in the vitellogenic region of the ovary just before the eggs close their pores; the sperm have now reached ten times their original size.