Comparative studies of testicular structure and sperm morphology among copulatory and non-copulatory sculpins (Cottidae: Scorpaeniformes: Teleostei)

Testicular structure of 9 species and sperm head morphology of 19 species of Cottidae were observed in order to clarify relationships between morphological characteristics of the male reproductive organ and reproductive mode (copulation or non-copulation). Morphological structure of the testis was divided into the following five types based on the sperm transfer and reservoir system: (1) a non-duct type in which the sperm duct is not a distinct exterior structure, but the tube for sperm transport traverses along the testis as an interior structure; (2) an anterior duct type with distinct anterior sperm ducts traversing along the testis; (3) a posterior duct type with distinct anterior sperm ducts traversing along the dorsal hilus of testis and posterior sperm ducts extending to the rear of the testis; (4) an anterior duct posterior vesicle type with distinct anterior sperm ducts traversing along the testis, and the right and left sperm ducts fusing in the rear of testis, forming the seminal vesicle; (5) a non-duct posterior vesicle type in which sperm ducts do not accompany the testis, and the testis and seminal vesicle are connected directly or through posterior sperm ducts. It is thought that in Cottidae the non-duct type of reproductive organ is primitive, and the anterior duct type is common to all non-copulating species. The testes and accompanying seminal vesicle were seen only in copulating species. Sperm head morphology was divided into three types according to the length/width ratio: oval type ≤2, intermediate type >2 and ≤3, and slender type >3. The type of sperm head corresponded closely to the reproductive mode; non-copulating species had oval sperm head, and copulating species had intermediate or slender ones. These results suggest that the structure of the testis and the morphology of the sperm head evolved from testes with anterior sperm ducts and oval sperm heads to testes with an associated seminal vesicle and slender sperm heads in association with the evolution from non-copulatory to copulatory reproduction in Cottidae.     

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.     

Ontogenetic testicular development and spermatogenesis in rays: the Cownose Ray,Rhinoptera bonasus,as a model

An understanding of testicular anatomy, development, and seasonality has implications for studies of morphology, behavior, physiology, and bioenergetics of males. Ontogenetic testicular development and spermatogenesis is essentially unknown for chondrichthyans. We examined embryo, juvenile, and adult male Cownose Rays (Rhinoptera bonasus) during development and throughout the annual reproductive cycle. Spermatogonia and Sertoli cells originated from germ cells and somatic cells, respectively, in the embryonic testicular germinal epithelium. In embryos and small juveniles, discrete regions of spermatocyst production appeared within a series of papillae that projected from the dorsal surface of each testis. Because these papillary germinal zones appeared to proliferate through ontogeny, we hypothesize that (1) the germinal zones of juvenile and adult testes are derived from embryonic testicular papillae that form from the germinal epithelium and (2) the papillae become the dorso-central portion of the distinct testicular lobes that form at maturation due to increased spermatocyst production. Our observations indicate that testicular development and the process of spermatogenesis began during embryonic development and increased in scale through ontogeny until maturation, when distinct testicular lobes formed and began enlarging or shrinking based on the annual reproductive cycle. Gonadosomatic indices peaked corresponding to seasonal increased sperm production between January and April, just prior to the April–June mating period. In all life stages, spermatocysts had efferent ducts associated with them from their formation through all stages of development. Year-round presence in the Charlotte Harbor estuarine system, Florida made R. bonasus a good model for beginning to understand ontogenetic gonad development and spermatogenesis in chondrichthyans, especially viviparous rays.     

A scanning electron microscopic study of germ cell maturation in the reproductive tract of the male soupfin shark (Galeorhinus galeus)

Germ cell maturation in the reproductive tract of the soupfin shark (Galeorhinus galeus) was studied using scanning electron microscopy (SEM). The SEM showed changes in Sertoli cytoplasm volume during spermatogenic development. In immature spermatocysts in the germinal zone, spermatogonia were embedded in Sertoli cytoplasm. In spermatogonial spermatocysts, Sertoli cells were adluminally located in the spermatocyst, with spermatogonia enveloped in the basal portions of the cytoplasm. During the round spermatid stage, Sertoli cytoplasm was very scanty. Spermatid elongation was accompanied by a progressive increase in the volume of Sertoli cytoplasm, notably around the spermatid heads. In the mature spermatocyst, bundles of spermatozoa are totally enveloped by Sertoli cytoplasm. Spermatozoa occurred randomly in the epididymis. However, in the ampulla ductus deferentis, spermatozoa reaggregated and were embedded in a mucoid substance to form highly ordered spherical bundles. In the sperm bundle, the spermatozoa heads were arranged such that the helical turns of adjacent spermatozoa were precisely aligned, and all the heads in the bundle formed a distinct apex. This study demonstrates the utility of exploring the relationship between germ cells and Sertoli cells in an evolutionarily ancient vertebrate, such as the shark.     

A study of gonadal organogenesis,and the factors influencing regeneration following surgical castration in Deroceras reticulatum (Pulmonata:Limacidae)

Summary At hatching, the hermaphrodite duct of Deroceras reticulatum consists of a single cell type designated the Gonadal Stem Cell (GSC). Proliferation of the GSC leads to the formation of numerous ductules each of which forms one of the acini of the gonad. The germinal and supporting cells are derived entirely from the GSC. The germ cells differentiate first, followed by the Sertoli and follicle cells. At the early sperm stage of gonadal development the hermaphrodite duct differentiates to function as a seminal vesicle. Once the GSC are committed to this change they lose their regenerative ability. The only remaining GSC are the cells of the acinar epithelium, and these retain their germinal potential until the death of the animal.Regeneration will occur from the hermaphrodite duct provided it is in the immature state, i.e., composed of GSC, and is exposed to the hormonal conditions of a young animal. Nervous connections and the presence of an artery are not necessary for this regeneration. The presence of a functional gonad does not inhibit regeneration.     

Ultrastructure of the male reproductive organs in the interstitial annelid Sphaerosyllis hermaphrodita (”Polychaeta”, Syllidae)

 The reproductive organs of the simultaneous hermaphrodite Sphaerosyllis hermaphrodita (Syllidae, Exogoninae) were examined by TEM and reconstructed from ultrathin serial sections. Oocytes are produced in the 11–13th chaetigerous segments and then attached to the outer body surface. The male organs comprise a seminal vesicle, testes, sperm ducts and copulatory chaetae. The unpaired seminal vesicle is an uncompartmented cavity above the gut and within the chaetigerous segments 8–10. Its interior is lined with a layer of gland cells that degenerate as spermatogenesis in the vesicle proceeds. The testes are situated ventrolaterally, close to the seminal vesicle in the 9th chaetigerous segment. They contain cells at early stages of spermatogenesis, which are connected to one another by zonulae collares. The testes and seminal vesicle are enclosed in epithelia. Paired sperm ducts run ventrally from about the midline of the body under the seminal vesicle and into the parapodia of the 9th chaetigerous segment. There they open, together with the protonephridia of this segment, to the outside next to the stout copulatory chaeta. Each sperm duct consists of six cells, the luminal surface of which bears microvilli but no cilia. Only in animals with fully differentiated sperm does the small opening of the proximal duct cell in each duct give access to the seminal vesicle. The mode of sperm transfer is discussed. Accepted: 9 December 1996     

The seminal vesicle of the African catfish,Clarias gariepinus

Summary The seminal vesicle of the African catfish, Clarias gariepinus, consists of 36–44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. In this fluid sperm cells are stored. The seminal vesicle fluid immobilizes the sperm cells. After ejaculation, it prolongs the period of sperm activity. The seminal vesicle fluid is secreted by the epithelium lining the tubules. The tubules in the proximal part of the lobes are predominantly lined by a simple cylindrical and those of the distal part by a simple squamous epithelium. These epithelial cells contain enzymes involved in energy-liberating processes, the enzyme activites being proportional to the height of the cells. Interstitial cells between the tubules have enzyme-histochemical and ultrastructural features indicative of steroid biosynthesis. Similar characteristics are found in testicular interstitial cells. The most rostral seminal vesicle lobes and the most caudal testicular efferent tubules form a network of tubules that opens at the point where the paired parts of the sperm ducts fuse with each other. The tubules of most seminal vesicle lobes, however, form a complex system that fuses with the unpaired part of the sperm duct.     

多肠目薄背涡虫生殖系统结构及一氧化氮合酶组化研究

运用常规组织学方法和NADPH-d组织化学方法,研究了薄背涡虫 Notoplana humilis 生殖系统的组织结构和一氧化氮合酶的分布.其雄性生殖系统包括精巢、储精囊、阴茎、雄性生殖孔,精巢壁由一薄层薄膜组成,每个精巢内都含有不同发育时期的雄性生殖细胞,且精子发育无明显同步性;储精囊呈螺旋状排列在雄性生殖孔附近,囊壁由单层扁平上皮组成;阴茎为粗大的球形,外壁由柱状上皮细胞和数层肌细胞组成.雌性生殖系统包括输卵管、生殖腔、雌性生殖孔和受精囊,但不形成集中的卵巢和卵黄腺.雌雄生殖孔、生殖腔、受精囊、阴茎等部位呈NADPH-d强阳性反应.     

Fine structure of leydig and sertoli cells in the testis of immature and mature spotted ray Torpedo marmorata

An ultrastructural investigation revealed the presence of true Leydig cells in the testis of sexually mature specimens of Torpedo marmorata. They showed the typical organization of steroid-hormone-producing cells, which, however, changed as spermatocysts approached maturity. In fact, they appeared as active cells among spermatocysts engaged in spermatogenesis, while in regions where spermiation occurred, they progressively regressed resuming the fibroblastic organization typically present in the testis of immature specimens. Such observations strongly suggest that these cells might be engaged in steroidogenesis and actively control spermatogenesis. Sertoli cells, too, appeared to play a role in spermatogenesis control, since, like Leydig cells, they showed the typical aspect of steroidogenic cells. In addition, the presence of gap junctions between Sertoli cells suggests that their activity might be coordinated. After sperm release, most Sertoli cells were modified and, finally, degenerated, but few of them changed into round cells (cytoplasts) or round cell remnants, which continued their steroidogenic activity within the spermatocyst and the genital duct lumen. From the present observations, it can be reasonably concluded that, in T. marmorata, spermatogenesis depends on both Leydig and Sertoli cells, and, as postulated by Callard (1991), in cartilaginous fish, the function of the Leydig cells as producers of steroids might be more recent and subsequent to that of Sertoli cells. In this regard, it is noteworthy that, in immature males, when Leydig cells showed a fibroblastic organization, Sertoli cells already displayed the typical organization of a steroidogenic cell.     

Developmental sequence for the copulatory organs of Kontikia mexicana with remarks on taxonomic significance (Turbellaria: Tricladida: Geoplanidae)

Five specimens, presumably representing different developmental stages of the land planarian Kontikia mexicana (Hyman, 1939), were used to reconstruct the development of the copulatory apparatus in this species. The results support the notion that Kontikia differs from the closely related Caenoplana in its possession of a penis papilla. In the earliest stage available, a penis papilla was absent and other components were not differentiated. In a late-juvenile condition, the gonopore, seminal vesicle, and ejaculatory duct were present. The short penis papilla appeared to arise in this stage by elongation of the terminal tissue around the ejaculatory duct and its separation from the antral wall. The female canal was guarded by an epithelial fold and the glandular duct was present. In the mature condition, the penis papilla was more elongate, and the secretory (prostatic) region of the ejaculatory duct was functional. The female canal, guarded by an epithelial fold, was well-developed with enlarged glandular duct but lacking the posterior diverticulum and the sperm storage system associated with the ovovitelline ducts known in Kontikia orana Froehlich, 1955.     

Observations on the ultrastructure of the copulatory organ of Archilopsis unipunctata (Fabricius, 1826) (Proseriata,Monocelididae)

The copulatory organ in adult specimens of Archilopsis unipunctata has been studied by transmission electron microscopy.This copulatory organ is of the conjuncta-duplex type with eversible cirrus. The seminal vesicle, lined with a nucleate epithelium, is surrounded by spirally arranged muscles. The fibres are enclosed in a sheath that is continuous with the septum of the bulbus and the basement lamina of the male canal epithelium. Distally to the seminal vesicle the bulbus is filled with the secretory cell-necks of the prostate glands. The male canal shows three different parts: seminal duct, ejaculatory duct and eversible cirrus. At the transition of seminal duct and ejaculatory duct two prostate ducts open into the lumen. The structure of the epithelium lining the different parts of the canal is described. The transition into the cirrus may be recognized by an abrupt change in the thickness, the electron density and the stratification in the basement lamina and by the disappearance of the epithelium absent indeed in the cirrus. The material found inside the cirrus-lumen is different according to the zone considered. The origin of this material and of the cirrus teeth is discussed.Abbreviations ab- apoptotic body - ba- bacteria - bb- basal bodies of cilia - bl- basement lamina - bw- body wall - c- cilia - cb- cell body - cgp- common genital porus - ci- cirrus - cip- cirrus plug - cl- lumen of cirrus - cm- circular muscles - cr- cytoplasmatic remnants - cs- cytoplasmatic sheets - ejd- ejaculatory duct - ep_ej- epithelium of ejaculatory duct - d- desmosomes - f- flagella of spermatozoa - fd- female duct - fp- female porus - gc- golgi complex - gl- glycogen particles - hd- hemidesmosomes - lm- longitudinal muscles - ly- lysosome-like body - m- muscles - m_b- muscles of the bulbus - m_c- muscles of the cirrus - m_c- muscles of the seminal vesicle - mi- mitochondria - ml- microvilli - ms- mesenchyme - n_sd- nuclei of the seminal duct - pd- prostate duct - pg- prostate glands - ri- ribosomes - s- septum - sb- secretory vesicle - sd- seminal duct - sp- spines - sv- seminal vesicle - v- vagina - vd- vas deferens     

Sinohesione genitaliphora gen. et sp. n. (Polychaeta, Hesionidae), an interstitial annelid with unique dimorphous external genital organs

A new hesionid. Sinohesione genitaliphora gen. et sp. n., is described from intertidal sandy sediments of Hainan Island, China. It differs from hitherto known hesionids by the presence of external genital organs in both sexes. In the males there is one pair of sae-like appendages, each bearing a tube-shaped penis, on chaetiger 10. In the females the paired sae-shaped organs are situated on chaetiger 12. Reconstructions of semi- and ultrathin sections show that a long, heavily coiled sperm duct opens at the tip of each penis. The duct opens with a ciliated funnel into a seminal vesicle in chaetiger 9. Prominent gland cells surround the sperm duct for the most part. The female genital organs each have two openings; one of which leads to a blind ending seminal receptacle. The other is the external pore of a ciliated oviduct that originates as an open funnel in the coelom of chaetiger 10. The functional and phylogenetic significance of these structures is discussed.     

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.     

Ultrastructural observations of the spermatogenesis of the hermaphroditic solitary coral Balanophyllia europaea (Anthozoa, Scleractinia)

Spermatogenesis ultrastructure was studied in a simultaneous hermaphrodite population of the solitary coral Balanophyllia europaea. In this species, spermatogenesis takes place in spermatocysts located within gametogenetic mesenteries surrounded by a bilayered boundary. Spermatogonia and spermatocytes are large flagellate cells, densely packed at the outermost edges of the spermatocyst. Spermatids and sperm are loosely distributed near the centre of the spermatocyst. The cytoplasm of spermatogonia and primary spermatocytes often contains short lengths of free axonemes, probably derived from the reabsorption of a primitive flagellum. Maturing spermatids either contain long intracytoplasmic axonemes, that may be stages of the tail synthesis, or have a flagellum. The morphological features of the sperm of this hermaphroditic scleractinian, very similar to those observed in the sperm of gonochoric taxa, support the hypothesis that the hermaphroditism of this population is an adaptive condition. Accepted: 1 October 1999     

Internal anatomy and ultrastructure of the male reproductive system of the spider crab Maja brachydactyla (Decapoda: Brachyura)

The morphology and function of the male reproductive system in the spider crab Maja brachydactyla, an important commercial species, is described using light and electron microscopy. The reproductive system follows the pattern found among brachyuran with several peculiarities. The testis, known as tubular testis, consists of a single, highly coiled seminiferous tubule divided all along by an inner epithelium into germinal, transformation, and evacuation zones, each playing a different role during spermatogenesis. The vas deferens (VD) presents diverticula increasing in number and size towards the median VD, where spermatophores are stored. The inner monostratified epithelium exocytoses the materials involved in the spermatophore wall formation (named substance I and II) and spermatophore storage in the anterior and median VD, respectively. A large accessory gland is attached to the posterior VD, and its secretions are released as granules in apocrine secretion, and stored in the lumen of the diverticula as seminal fluids. A striated musculature may contribute to the formation and movement of spermatophores and seminal fluids along the VD. The ejaculatory duct (ED) shows a multilayered musculature and a nonsecretory pseudostratified epithelium, and extrudes the reproductive products towards the gonopores. A tissue attached to the ED is identified as the androgenic gland.     

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.     

Morphology of the reproductive tract and acquisition of sexual maturity in males of Potamotrygon magdalenae (Elasmobranchii: Potamotrygonidae)

The purpose of this study was to describe the structure of the reproductive tract of males of Potamotrygon magdalenae before, during, and after they acquire sexual maturity, and to establish the first maturity scale for males within the family Potamotrygonidae. The male reproductive tract of P. magdalenae is composed of testes, efferent ducts, epididymides, deferent ducts, seminal vesicles, Leydig, alkaline, and clasper glands, and claspers, all of which are paired and functional. Four sexual maturity stages were established: immature, maturing, reproductively active, and resting. The degree of claspers calcification is also a good indicator of sexual maturity in this species. The testes are lobulated, each lobe contains numerous spermatocysts which are organized in zones and are displaced radially from germinal papillae to the spermatozoa zone where individual spermatozoa are conveyed to the efferent ducts. The epididymis can be regionalized in head, body, and tail; these regions are distinguished by external pigmentation and by the epithelium lining configuration. The tail of the epididymis is connected with the deferent duct and this, in turn, with the seminal vesicle. The spermatozoa are organized in spermatozeugmata which begin to form in the deferent duct; this latter organ is attached laterally at the Leydig gland that is composed by simple glandular units. Irregular and vesicular secretions can be found in the genital ducts. These secretions might be associated with the maturation of the spermatozoa and formation of spermatozeugmata. The male reproductive tract of P. magdalenae is similar to other elasmobranchs; however, two types of primary spermatogonia, an epididymis internally regionalized, and the presence and structure of spermatozeugmata are specific features not yet described in freshwater stingrays. Most of the year, the males were reproductively active, however, few resting adult males occurred during one of the months of the lowest waters. J. Morphol. 276:273–289, 2015. © 2014 Wiley Periodicals, Inc.     

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.     

The sperm roller: a modified testicular duct linked to giant sperm transport within the male reproductive tract

The male reproductive tracts of Drosophila display considerable variation in the relative size of their components, notably of the testes, but there are few structural differences between species. Here we report a remarkable coiled structure separating the testes from the seminal vesicles in the giant sperm species Drosophila bifurca. This evolutionary novelty, known as the 'sperm roller', seems to be an exaggeration in the size of the testicular duct as revealed by light and electron microscopic observations. It consists of a tubular monocellular epithelium lying on the basal laminae and muscle and conjunctive cells. The lumen of the roller contains crypts. The apical membrane of the epithelial cells presents numerous long microvilli protruding into the lumen. The sperm roller structure is probably involved in managing sperm during their transit through the male genital tract, because sperm are seen in bundles at the base of the testis, whereas they are singly rolled up by the time they enter the seminal vesicles. The hypercoiling of the individual spermatozoon within the roller probably occurs as the result of an osmotic process produced by features of the epithelial wall and the dramatically increased exchange surface. This is the first report of a specialized device of this type in Drosophila or, more generally, in insects.     

A novel occluding junction which lacks membrane fusion in insect testis

Spermatocysts develop within the lumina of the lepidopteran testis. Each spermatocyst contains a clone of maturing germ cells which are separated from the fluid in the testicular lumen by a layer of somatic envelope cells. A blood-testis barrier is located at the level of the somatic envelope cells. We used macromolecular tracers horseradish peroxidase (applied before fixation) and ruthenium red (applied during fixation) with thin sections and freeze-fracture replicas to study the nature of this barrier in spermatocysts of the tobacco budworm, Heliothis virescens. Movement of the tracers into the spermatocysts was blocked by a structure at the outer edge of the septate junctions which join the spermatocyst envelope cells. In freeze-fracture replicas there was a P-face ridge or an E-face groove in this location. The ridge/groove appeared similar to a single-stranded vertebrate tight junction. Unlike tight junctions, however, there was no fusion or even close apposition of adjacent cell membranes in this location. We conclude, therefore, that a novel type of occluding junction was the barrier to paracellular movement of macromolecules in Heliothis spermatocysts.