Aspects of germinal cyst and sperm development in Poecilia latipinna (Teleostei: Poeciliidae).

The structure of the testis of Poecilia latipinna is described with particular reference to Sertoli cell-germ cell relationships during development and maturation of the germinal cyst. The cyst develops when primary spermatocytes become surrounded by a single layer of Sertoli cells at the testis periphery. As spermatogenesis and then spermiogenesis proceed, the cyst moves centrally in the testis toward the ducts comprising the vasa efferentia. In addition to being a structural part of the germinal cyst, the Sertoli cells phagocytize residual bodies cast off by developing spermatids and form an association with mature bodies cast off by developing spermatids and form an association with mature sperm, which resembles that observed in mammals, before the sperm are released into the vasa efferentia as a spermatozeugmata. The results of this investigation are discussed in view of what is known concerning testis structure in other teleosts and similarities between cell functions in teleosts and mammals. It is concluded that teleost Sertoli cells, teleost lobule boundary cells and mammalian Sertoli cells are homologous.     

Structure of the testis and spermatogenesis of the viviparous teleost Poecilia mexicana (Poeciliidae) from an active sulfur spring cave in Southern Mexico

We describe the histological characteristics of the testis and spermatogenesis of the cave molly Poecilia mexicana, a viviparous teleost inhabiting a sulfur spring cave, Cueva del Azufre, in Tabasco, Southern Mexico. P. mexicana has elongate spermatogonial restricted testes with spermatogonia arranged in the testicular periphery. Germ cell development occurs within spermatocysts. As spermatogenesis proceeds, the spermatocysts move longitudinally from the periphery of the testis to the efferent duct system, where mature spermatozoa are released. The efferent duct system consists of short efferent duct branches connected to a main efferent duct, opened into the genital pore. Spermatogenesis consisted of the following stages: spermatogonia (A and B), spermatocytes (primary and secondary), spermatids, and spermatozoa. The spermatozoa are situated within spermatocysts, with their heads oriented toward the periphery and flagella toward the center. Once in the efferent duct system, mature spermatozoa are packaged as unencapsulated sperm bundles, that is, spermatozeugmata. We suggest that the histological characteristics of the testis and spermatogenesis of P. mexicana from the Cueva del Azufre, and the viviparous condition where the spermatozoa enter in the female without been in the water, have allowed them to invade sulfurous and/or subterranean environments in Southern Mexico, without requiring complex morphofunctional changes in the testis or the spermatogenetic process.     

Ultrastructure and histochemistry of the testicular efferent duct system and spermiogenesis in Opistognathus whitehurstii (Teleostei, Trachinoidei)

 Testis organization and spermatogenesis, with the emphasis on spermiogenesis, in Opistognathus whitehurstii are described by ultrastructural and histochemical methods. The germinal epithelium is extremely reduced and restricted to the periphery of the testis, while most of the organ is occupied by a highly developed system of testicular efferent ducts. A semicystic type of spermatogenesis is observed and in the germinal epithelium spermatogenesis occurs only until the spermatidal stage. Young spermatids are released into the lumen of the testicular lobules and mature to sperm within the efferent duct system. The epithelial cells of these ducts are involved in protein and glycogen secretion and in phagocytosis of degenerating germ cells and residual bodies cast off by developing spermatids. On the basis of these functions, the testicular efferent duct system cells are considered to be homologous to the Sertoli cells. A correlation between a highly developed testicular efferent duct system and semicystic spermatogenesis is examined and a possible functional meaning of this apparently unusual mode of sperm production is proposed. Accepted: 18 March 1997     

Cellular Organization of the Testis and Spermatogenesis in Fishes

SYNOPSIS. Tubular structure of the teleost testis can be dividedinto two basic types distinguished from each other by the distributionof spermatogonia. In most teleosts, spermatogonia occur alongthe length of the tubules, but in atheriniform fishes they areconfined to the terminus of the tubule. Variations in thesetestis-types are discussed particularly in light of modificationsleading to the production of spermatozeugmata or spermatophores. Teleost boundary cells are located immediately outside of thetubule basement membrane. Previous reports homologizing "lobuleboundary cells" with Leydig or Sertoli cells are in error. Leydigcells have been described for species of teleosts wherein theyhave previously been thought to be absent and are a typicalcomponent of the interstitium. Sperm morphology reflects mode of reproduction. Nuclear elongation,coupled with possible elongation of the sperm midpiece, is characteristicof most species wherein fertilization is internal. Teleost spermlack an acrosome.     

Structure of the Testes,Spermatozoa and Spermatozeugmata of Mimagoniates barberiRegan, 1907 (Teleostei: Characidae), an Internally Fertilizing,Oviparous Fish

Abstract The testis of Mimagoniates barberiis bipartite. Spermatogenic tissue is restricted to the anterior part. The posterior part of the testis is devoid of spermatogenic tissue and contains numerous efferent ducts filled with mature sperm. Cells in germinal cysts develop synchronously, sperm nuclei and flagella become oriented parallel in the late stages of spermiogenesis. In the caudal portion of the aspermatogenic part all sperms are arranged into unencapsulated sperm bundles — spermatozeugmata. Two types of spermatozeugmata are found both in the caudal portion of the testis and in milt. In the larger, spindle–shaped type, sperm flagella form the spindle tips. In the smaller ones, which have approximately a length of spermatozoon, the sperm are parallel and approximately in register. In both types sperm heads are arranged parallel. A mature spermatozoon is flail–shaped. The sperm head is highly elongated and situated alongside the flagellum, the tip of the head is directed backwards. Large mitochondria are situated on one side of the elongated nucleus only and form the tip of the head. Live spermatozoa move with the centriolar part ahead. Both testis and spermatozoon structure as well as formation of spermatozeugmata in M. barberiare highly derived features which perhaps evolved as adaptations to internal fertilization.     

The origin and fate of spermatophores in the viviparous teleost Cymatogaster aggregata (Perciformes: Embiotocidae)

The sperm of the shiner surfperch are packaged into high density aggregations which are introduced into the female genital tract at insemination. Germ cell differentiation occurs within cysts formed by nongerminal Sertoli cells. In late spermiogenesis, spermatozoa within the cysts come to lie parallel to each other and become more densely packed. These sperm packets (spermatophores), containing approximately 600 spermatozoa, then are released into the efferent sperm ducts. The exact nature of the spermatophore binding material is not known, but a major component is proteinaceous and is synthesized in the rough endoplasmic reticulum of the efferent sperm duct epithelial cells. The mechanism by which the spermatophores pass from cysts into ducts is not clear. It appears that whereas many Sertoli cells degenerate causing the cyst wall to break down, many Sertoli cells do not degenerate, but rather assume the configuration of columnar duct cells. The spermatophores remain intact within the testicular ducts, but rapidly dissolve within the female ducts in response to increased pH.     

Testis morphology and spermatozeugma formation in three genera of viviparous halfbeaks: Nomorhamphus,dermogenys, and Hemirhamphodon (Teleostei: Hemiramphidae)

The testes of 19 species of viviparous halfbeaks from three genera, Nomorhamphus, Dermogenys, and Hemirhamphodon, are examined histologically. The testes are unfused, paired organs running laterally along the body wall on either side of the gut. In all genera, primary spermatogonia are restricted to the distal termini of the testicular lobules just beneath the tunica albuginea, conforming to the typical atherinomorph testis type. The short efferent ducts empty into a single longitudinal main duct in each testis. All species package sperm in the form of unencapsulated sperm bundles, which are referred to as spermatozeugmata. The mechanism of packet formation and the resulting spermatozeugmata are similar in all five species of Nomorhamphus and in four species of Dermogenys, with each spermatocyst releasing several small spermatozeugmata. In the other four species of Dermogenys, the mechanism of packet formation is similar, and each spermatocyst releases a single, large spermatozeugma. The spermatozeugmata of six species of Hemirhamphodon are unlike those seen in the other two genera, with five different sperm bundle types described herein. The unique sperm bundles of the viviparous halfbeaks are compared with those of the internally fertilizing but oviparous halfbeak genus, Zenarchopterus, discussed within a phylogenetic framework, and hypothesized to be independently derived within the Atherinomorpha. © 1995 Wiley-Liss, Inc.     

Localization of acid phosphatase activity in the testis of two teleostean species (Oreochromis niloticus and Odonthestes perugiae).

Acid phosphatase (AcP) activity was investigated in the testes of two species of teleosts in two seasons: summer and winter. AcP activity was detected in Sertoli cells from tilapia (Oreochromis niloticus) only during the nonreproductive period of its annual cycle, corresponding to the winter months. In kingfish (Odonthestes perugiae), the enzymatic reaction was identified during the non-reproductive period (summer) in epithelial cells of the efferent ducts but not in Sertoli cells. These data suggest that the enzyme is involved in the absorption of residual spermatid cytoplasm and as well as in the removal of spermatozoa remaining after the reproductive period. In kingfish, this heterophagous function is carried out by the efferent duct cells and not by Sertoli cells.     

Reproductive histology of Tomeurus gracilis Eigenmann, 1909 (Teleostei: Atherinomorpha: Poeciliidae) with comments on evolution of viviparity in atherinomorph fishes

Tomeurus gracilis is a species long considered pivotal in understanding the evolution of livebearing in atherinomorph fishes. Tomeurus gracilis is a zygoparous or embryoparous poeciliid: internal fertilization is followed by females laying fertilized eggs singly or retaining fertilized eggs until or near hatching. Tomeurus was hypothesized as the sister group of the viviparous poeciliids until it was proposed as a close relative of a derived viviparous poeciliid, Cnesterodon, hence nested among viviparous taxa rather than near the root of the tree. Here, we describe and compare reproductive morphological characters of the little‐known Tomeurus with those of representative atherinomorphs. In Tomeurus and Cnesterodon, sperm are packaged in naked sperm bundles, or spermatozeugmata, in a configuration considered here diagnostic of viviparous poeciliids. Testes are single and free sperm are stored in the ovary in both taxa in contrast to oviparous atherinomorphs in which testes are paired and sperm are not packaged and not stored in the ovary. Efferent ducts in Cnesterodon testes and other viviparous poeciliids have a PAS‐positive secretion demonstrating presence of a glycoprotein that inactivates sperm or prevents final sperm maturation. No PAS‐positive staining secretion was observed in Tomeurus or oviparous atherinomorphs. Tomeurus shares apomorphic reproductive characters, such as sperm bundle and testis morphology and a gonopodium, with viviparous poeciliids and plesiomorphic characters, such as a thick zona pellucida with filaments, with oviparous taxa. We do not postulate loss or reversal of viviparity in Tomeurus, and we corroborate its phylogenetic position as sister to the viviparous poeciliids. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

A sex cord‐like structure and some remarkable features in early gonadal sex differentiation in the marine teleost Siganus guttatus(Bloch)

Several notable features of early gonadal sex differentiation in the golden rabbitfish Siganus guttatus are described including the first report among teleosts of a distinctive dual structure, consisting of somatic cells directly enclosing germ cells (sex cord‐like structure, SCS) and outer somatic tissue surrounding the SCS, in both undifferentiated and early differentiated gonads. Germ cells occurred and proliferated exclusively in the SCS during the process of ovarian and testicular differentiation. A second remarkable characteristic was the delayed germinal cell proliferation for oogenesis in the ovary, that commenced simultaneously with that in the testis, a relatively long time after the onset of somatic development. These observations suggest the possibility that sex differentiation of germ cells is preceded by some sex specific changes in somatic components of the SCS that are light‐microscopically indistinguishable between the sexes. The third unique feature was the detachment of gonadal tissue, including both somatic and germ cells, into the ovarian cavity in the ovary and into the seminiferous lobules and main seminal duct in the testis. This phenomenon occurred in the testis, forming the efferent duct network after 73 days post‐hatch (DPH), and in the ovaries, forming the ovigerous lamellae and regulating the number of oocytes attaining full maturation at c . 129 DPH.     

Expression of nerve growth factor (NGF), and its receptors TrkA and p75 in the reproductive organs of the adult male rats

Immunolocalization of nerve growth factor (NGF) and its receptors, TrkA and p75 in the reproductive organs of adult male rats was investigated. Sections of the testis, efferent duct, epididymis, deferent duct, seminal vesicle, coagulating gland and prostate of adult male rats were immunostained by the avidin-biotin-peroxidase complex methods (ABC). NGF was expressed in Leydig cells, primary spermatocytes and pachytene spermatocytes in the testis. TrkA only immunoreacted to elongate spermatids and p75 showed positive immunostaining in the Sertoli cells, Leydig cells, the pachytene spermatocytes and elongate spermatids. Immunoreactions for NGF and its two receptors were detected in epithelial cells of efferent duct, deferent duct and epididymis. In addition, immunoreactions for NGF and its two receptors were also observed in columnar secretory epithelium lines of the seminal vesicles, prostate and coagulating gland. These results suggest that NGF is an important growth factor in gonadal function of adult male rats.     

A light and electron microscopic study on the organization of the testis and the semicystic spermatogenesis of the genus Scorpaena (Teleostei,Scorpaenidae)

The testicular organization and semicystic spermatogenesis of Scorpaena porcus and Scorpaena scrofa are analyzed by means of optic and electron microscopy and immunohistochemical techniques. The testicular structure of S. porcus and S. scrofa belongs to the unrestricted spermatogonial type, but has typical features of the restricted type. Moreover, the structure presents an epithelioid arrangement of Sertoli and germ cells rather than the germinal epithelium that appears in the majority of teleosts. After the cysts open, Sertoli cells hypertrophy and remain on the basement membrane, linked by interdigitations and tight junctions and bordering the lumen of the lobule, which at this moment works as an efferent duct. Secretions of Sertoli cells usually function in the nutrition of germ cells, and they seem to contribute in it even in this kind of spermatogenesis in which the free lumen spermatids do not have any connection with Sertoli cells. In addition, Sertoli cells can divide after the cysts have broken apart and hypertrophied, suggesting that they are still important for the final maturation of spermatozoa and seminal fluid formation. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Structure of the testis and genital duct of freshwater stingray, Himantura signifer (Elasmobranchii: Myliobatiformes: Dasyatidae)

The light microscopic structure of the testis and genital duct system of the freshwater stingray Himantura signifer was observed. The testis is composed of lobes having numerous spermatocysts in a dorsoventral zonated arrangement. The germinal papilla at the middorsal surface of the testicular lobe is the origin site of spermatocyst development, where mesenchymal-like cells are predominantly found. The association of a Sertoli cell precursor with a spermatogonium marks the onset of spermatocyst formation and development. The newly formed spermatocysts at the dorsal end of the germinal zone replace the older ones, which are sequentially moved to the ventral side and are termed spermatogonial, spermatocyte, spermatid, spermatozoal, and degenerate zones. In the degenerate zone, the spermatocysts deteriorate after releasing the spermatozoa into the intratesticular duct, where they are further transported through the extratesticular duct system and finally stored at the seminal vesicle. The epithelial lining of the genital duct is a pseudostratified ciliated columnar with no muscular layer underneath; thus, sperm are conveyed through ciliary activity. The interesting features of the present study are the finding of mesenchymal-like cells in the germinal papilla and the nonaggregated formation of sperm in the seminal vesicle.     

Cathepsin A is expressed in a cell- and region-specific manner in the testis and epididymis and is not regulated by testicular or pituitary factors.

The epithelial cells of the testis are involved in the production, differentiation, and sustenance of sperm, and those of the epididymis play a major role in sperm maturation, protection, and storage. These tissues express various proteins that respond differently to androgens. Cathepsin A is a multifunctional lysosomal carboxypeptidase that also functions as a protective and an activator protein for neuraminidase and beta-galactosidase. In this study, cathepsin A was immunolocalized by light and electron microscopy using a polyclonal affinity-purified antibody on the testis and epididymis of normal, orchidectomized with or without testosterone supplementation, efferent duct-ligated, and hypophysectomized adult rats. In normal rats, cathepsin A expression was noted in lysosomes of Sertoli and Leydig cells but not in germ cells of the testis, as well as nonciliated cells of the efferent ducts. In the epididymis, a cell- and region-specific distribution of cathepsin A was noted. In experimentally treated animals, no changes were noted in the expression of cathepsin A. Immunolabeling of tissues examined at the electron microscopic level revealed that lysosomes were reactive. These data indicate cell- and region-specific expression of cathepsin A in cells of the testis and epididymis and also indicate that cathepsin A expression is not regulated by testicular or pituitary factors.     

Ultrastructure of sperm storage and male genital ducts in a male holocephalan, the elephant fish, Callorhynchus milii.

In chondrichthyes, the process of spermatogenesis produces a spermatocyst composed of Sertoli cells and their cohort of associated spermatozoa linearly arrayed and embedded in the apical end of the Sertoli cell. The extratesticular ducts consist of paired epididymis, ductus deferens, isthmus, and seminal vesicles. In transit through the ducts, spermatozoa undergo modification by secretions of the extratesticular ducts and associated glands, i.e., Leydig gland. In mature animals, the anterior portion of the mesonephros is specialized as the Leydig gland that connects to both the epididymis and ductus deferens and elaborates seminal fluid and matrix that contribute to the spermatophore or spermatozeugmata, depending on the species. Leydig gland epithelium is simple columnar with secretory and ciliated cells. Secretory cells have periodic acid-Schiff positive (PAS+) apical secretory granules. In the holocephalan elephant fish, Callorhynchus milii, sperm and Sertoli cell fragments enter the first major extratesticular duct, the epididymis. In the epididymis, spermatozoa are initially present as individual sperm but soon begin to laterally associate so that they are aligned head-to-head. The epididymis is a highly convoluted tubule with a small bore lumen and an epithelium consisting of scant ciliated and relatively more secretory cells. Secretory activity of both the Leydig gland and epididymis contribute to the nascent spermatophores, which begin as gel-like aggregations of secretory product in which sperm are embedded. Fully formed spermatophores occur in the ductus. The simple columnar epithelium has both ciliated and secretory cells. The spermatophore is regionalized into a PAS+ and Alcian-blue-positive (AB+) cortex and a distinctively PAS+, and less AB+ medulla. Laterally aligned sperm occupy the medulla and are surrounded by a clear zone separate from the spermatophore matrix. Grossly, the seminal vesicles are characterized by spiral partitions of the epithelium that project into the lumen, much like a spiral staircase. Each partition is staggered with respect to adjacent partitions while the aperture is eccentric. The generally nonsecretory epithelium of the seminal vesicle is simple columnar with both microvillar and ciliated cells.     

Intermediate filaments in the testis of the teleost mosquito fish Gambusia affinis holbrooki: a light and electron microscope immunocytochemical study and Western blotting analysis

Summary A light and electron microscope immunocytochemical study and Western blotting analysis has been performed on intermediate filaments (vimentin, desmin and cytokeratins) in the testis of the teleost fish Gambusia affinis holbrooki. An immunoreaction to vimentin was observed in the epithelium of the efferent ducts, testicular canal and their surrounding peritubular cells. Positive vimentin immunostaining was also observed in the cells located around seminiferous tubules (boundary cells), Leydig cells, interstitial fibroblasts, chromatophores, and blood vessel endothelial cells. In contrast to mammals, no vimentin immunoreactivity was found in the Sertoli cells. Immunoreactivity to desmin was weak in the epithelial cells of the efferent ducts and testicular canal and intense in the peritubular cells that surrounded these ducts. Desmin immunoreactivity was also observed in the seminiferous tubule boundary cells. The immunoreactivity was weak in the boundary cells that surrounded germ cell cysts containing spermatogonia or spermatocytes and intense in the boundary cells around cysts with elongated or mature spermatids. Immunoreactivity towards cytokeratins was observed only in testicular blood vessels. Cytokeratin immunolabelling was intense in the endothelium and weak in the vascular smooth muscle cells. No cytokeratin immunoreactivity was found in the Sertoli cells, germ cells, interstitial cells or in the efferent duct epithelium. The absence of intermediate filaments in the Sertoli cells, the absence of cytokeratins in the epithelium of the sperm excretory ducts, and the presence of desmin filaments in these epithelial cells are the most important differences with regards to the intermediate filament phenotype in mammalian testes.     

Annual changes in germinal epithelium determine male reproductive classes of the cobia

Five reproductive classes of cobia Rachycentron canadum , caught along the Gulf of Mexico and the south-east Atlantic coast of the U.S.A., are described during the annual reproductive cycle. These are based upon changes in the testicular germinal epithelium and the stages of germ cells that are present: early maturation, mid maturation, late maturation, regression and regressed. During early maturation, the germinal epithelium is continuous from the testicular ducts to the periphery of the testis and active spermatogenesis occurs throughout the testis. In mid maturation, the germinal epithelium near the ducts becomes discontinuous, but it remains continuous distally. In late maturation, a discontinuous germinal epithelium extends all along the lobules to the testicular periphery; lobules are swollen with sperm and there is minimal spermatogenesis. The regression class is characterized by a discontinuous epithelium throughout the testis, sperm storage and widely scattered spermatocysts. Spermatogonial proliferation also occurs along the lobule walls and at the periphery of the testis. In regressed testes, spermatogonia exist only in a continuous or discontinuous germinal epithelium, although residual sperm are nearly always present in the lobules and ducts. The presence or absence of sperm is not an accurate indicator of reproductive classes. At the periphery of the testis in the regression and regressed classes, the distal portions of lobules elongate as cords of cells containing spermatogonia and Sertoli cells. All reproductive classes can be identified in paraffin sections, although plastic sections provide better resolution. Using maturation classes defined by changes in the germinal epithelium to describe testicular development and spermatogenesis gives a more accurate picture than does using the traditional terminology.     

Spermiogenesis in Psilochorus simoni (Berland, 1911) (Pholcidae, Araneae): evidence for considerable within-family variation in sperm structure and development

A large number of characters and considerable variation among taxa make animal sperm cells promising objects for phylogenetic studies. However, our knowledge about sperm structure and development in spiders is still rudimentary. In pholcids, previous studies of two species representing different subfamily level taxa have revealed conspicuous differences. Here, we report on a representative of a third subfamily level taxon, confirming substantial variation in sperm structure and development within the family. The male genital system in Psilochorus simoni (Berland, 1911) consists of paired testes and deferent ducts which lead into a common ejaculatory duct. The somatic cells of the testes show a high secretory activity, and produce at least two different kinds of secretion. The spermatozoa show features already known from other Pholcidae as well as unique characters. The acrosomal vacuole is tube-like with a narrow subacrosomal space. The axoneme migrates deep into the nucleus and is finally located near the acrosomal vacuole. Thus, the postcentriolar elongation of the nucleus is very long. A centriolar adjunct is not present and after the coiling process the implantation fossa is completely filled with glycogen which is also found in larger amounts within the cytoplasm of the sperm cell. After the coiling process, a vesicular area is present that becomes most prominent in the periphery of the sperm cell and surrounds the axoneme and parts of the nucleus. The secretion sheath surrounding the mature spermatozoon is already formed in the lumen of the testis, possibly by a secretion present in the testis but absent in the deferent duct. Sperm are transferred as cleistospermia. Results are compared with previous studies on pholcid spermiogenesis and sperm structure.     

Histopathology of the male reproductive system induced by the fungicide benomyl

Benomyl is an effective fungicide that has been in use for many years. This chemical and its primary metabolite, carbendazim, are microtubule poisons that are relatively nontoxic to all mammalian organs, except for the male reproductive system. Its primary effects, at moderate to low dosages, are on the testis, where it causes sloughing of germ cells in a stage-dependent manner. Sloughing is caused by the effects of the chemical on microtubules and intermediate filaments of the Sertoli cell. These effects spread to dividing germ cells and also lead to abnormal development of the head of elongating spermatids. At higher dosages, it causes occlusion of the efferent ducts, blocking passage of sperm from the rete testis to epididymis. The mechanism of occlusion appears to be related to fluid reabsorption, sperm stasis, followed by leukocyte chemotaxis, sperm granulomas, fibrosis and often the formation of abnormal microcanals. The occlusion results in a rapid swelling of the testis and ultimately seminiferous tubular atrophy and infertility. In conclusion, studies that reveal long term testicular atrophy following chronic or subchronic exposure to a toxicant should be re-examined for histopathological lesions in the efferent ductules and head of the epididymis. Lesions in the male track that cause blockage may induce permanent testicular damage and a decrease in sperm production.     

On the nurse cell and the spermatozeugma in Littorina sitkana

Summary Nurse cells develop from diploid cells in the testis. Each cell undergoes a reduction division which leaves the nucleus with half the volume of a normal diploid cell. They send out pseudopodia which form desmosomelike junctions with developing spermatids. The nurse cells detach from the testicular wall, their nuclei degenerate and secretion droplets form in the cytoplasm. The pseudopodia are drawn in as the cytoplasmic secretions swell and the nurse cell becomes spherical. The eupyrene sperm become grouped unilaterally and at this stage are attached to the nurse cell by only the tips of their acrosomes. At maturity the nurse cells with their clumps of attached eupyrene sperm (spermatozeugmata) are released from the testis via ducts into the seminal vesicles, where they are stored prior to copulation. Nurse cells serve similar functions to those of apyrene sperm which are common among the Molluscs. We believe that the nurse cell and apyrene sperm are homologous.