Ultrastructural study of spermatogenesis in the free-living marine nematode <Emphasis Type="Italic">Paracyatholaimus pugettensis</Emphasis> Weiser et Hopper, 1967 (Chromadorida: Cyatholaimidae)

Spermatogenesis and the morphology of mature sperm in the free-living chromadorid Paracyatholaimus pugettensis from the Sea of Japan were studied using transmission electron microscopy. In spermatocytes fibrous bodies (FBs) appear; in spermatids, the synthetic apparatus is located in the residual body, whereas the main cell body (MCB) houses the nucleus, mitochondria, and FBs. The nucleus of the spermatid consists of a loose fibrous chromatin that is not surrounded by a nuclear envelope; centrioles lie in the perinuclear cytoplasm. The plasma membrane of the spermatid MCB forms numerous filopodia. Immature spermatozoa from the proximal part of the testis are polygonal cells with a central nucleus. The latter is surrounded by mitochondria and FBs with poorly defined boundaries. The immature spermatozoa bear lamellipodia all along their surface. Mature spermatozoa are polarized cells with an anterior pseudopodium, which is filled with filaments that make up the cytoskeleton; the MCB houses a nucleus that is surrounded by mitochondria and osmiphilic bodies. In many ultrastructural characteristics, the spermatozoa of P. Pugettensis are similar to those of most nematode species studied so far (i.e., they are ameboid, have no acrosome, axoneme, or nuclear envelope). On the other hand, as in other chromadorids, no aberrant membrane organelles were observed during spermatogenesis of P. Pugettensis.Original Russian Text Copyright © 2004 by Biologiya Morya, Zograf, Yushin.     

Formation of the acrosome and basal body during spermiogenesis in a marine snail,Nerita picea (Mollusca: Archaeogastropoda)

In Nerita picea the proacrosomal granule is formed basally in the early spermatid from one large cisterna of the Golgi body, with which the other Golgi-derived vesicles fuse. After the proacrosomal granule has attached to the plasma membrane and invaginated to form a cup shape, one cisterna of endoplasmic reticulum inserts into the open end and deposits a granular secretion on the inner surface. Subsequently, the proacrosome migrates along the plasma membrane to the apex of the nucleus, but the Golgi body remains basal, as occurs in other archaeogastropods and also many polychaete annelids. However, the final shape and structure of the acrosome is similar to that of mesogastropods. The annulus attaches the distal centriole to the plasma membrane early in spermiogenesis. The production of the flagellum by the distal centriole not only expands the plasma membrane posteriorly but moves the centriolar complex to the nucleus, causing an invagination of the plasma membrane where it is bound by the annulus. During proacrosome migration, the Golgi body secretes a dense tube around the flagellum, and the mitochondria fuse into two spheres at the base of the nucleus. The nuclear plug that closes off the intranuclear canal until this stage rapidly reorganizes itself into two tubes of material inside the canal. The centrioles continue flagellar production, break away from the annulus, and move deep into the intranuclear canal where they fuse together to form the basal body of the sperm. In the maturing spermatid, the two mitochondria fuse into a single sheath that spirals around the flagellum. The annulus does not migrate posteriorly but remains anterior to the midpiece, which is unusual for a filiform sperm. Spermiogenesis in Nerita picea has features in common with both archaeogastropods and mesogastropods but also has some unique features. These observations lend credence to the idea that the Neritidae are a transitional group between Archaeogastropoda and Mesogastropoda.     

Spermatogenesis in a Free-Living Marine Nematode Neochromadora poecilosoma (Chromadorida,Chromadoridae) Studied Using TEM

Spermatogenesis and the structure of mature spermatozoa were studied using TEM in a free-living marine chromadorid nematode Neochromadora poecilosoma from the Sea of Japan. In spermatocytes, fibrous bodies (FB) develop; in spermatids, the synthetic apparatus lies in the residual body, while the nucleus, mitochondria, and FB are located in the main cell body (MCB). The nucleus consists of a diffuse chromatin of fibrous structure, which is not enclosed in a nuclear envelope. In the spermatid stage, the development of FB is completed, and immature spermatozoa from the proximal region of the testis do not show any structural differences from the MCB of spermatids. The mature spermatozoa are polarized cells. They attach to the uterus wall by a pseudopod filled with filaments of the cytoskeleton; in the MCB of spermatozoon, there is a nucleus surrounded by mitochondria and osmiophilic bodies. The spermatozoa of N. poecilosoma show typical ultrastructure features of sperm cells found in most studied nematodes (amoeboid nature and the absence of axoneme, acrosome, and nuclear envelope). However, no aberrant organelles characteristic of nematode spermatozoa were found throughout sperm development in N. poecilosoma and other chromadorids.     

Fine structure of spermiogenesis with special reference to the spermatid morulae of the freshwater mussel Prisodon alatus (Bivalvia,Unionoidea)

Within the testicular cysts of the mussel Prisodon alatus are numerous somatic host cells described as Sertoli cells (SC), each containing a variable number of young spermatid morulae. Among them, several free spermatid morulae, spermatids, and spermatozoa were observed. Each free spermatid morula is surrounded by an external membrane. The early spermatids enclosed within the morulae have dense and homogeneous chromatin, and the cytoplasm occupies little space around the nucleus. Later, during spermiogenesis, the SC show lysis and disrupt to liberate the spermatid morulae. The membrane of the free morula is then disrupted, releasing the young spermatids. The SC disappear just after the appearance in the testis of a large number of free young spermatids. The nucleus of each free spermatid becomes gradually smaller and denser by the appearance of a granular pattern of condensed chromatin. During the maturation phase of the spermatids, the cytoplasm becomes more voluminous, and mitochondria and centrioles are more evident. Then, flagellogenesis occurs, and the nucleus gradually condenses into thicker strands. In the mature sperm, the apical zone has a disc-shaped acrosomal vesicle and the midpiece contains five mitochondria and two centrioles located at the same level. The flagellum has the common 9+2 microtubular pattern. The results are discussed with particular reference to Sertoli cells and clusters of spermatid morulae with those of species of closely related taxa in the bivalves. J. Morphol. 238:63–70, 1998. © 1998 Wiley-Liss, Inc.     

Ultrastructural observations on the male gametes in Austrognathia sp. (Gnathostomulida,Bursovaginoidea)

The male gametes of the gnathostomulid bursovaginoid Austrognathia sp. were investigated by electron microscopy. All stages of sperm development can be observed in the single saccular male gonad, which is enclosed by a relatively thick basement membrane internally reinforced by thin smooth muscle cells. The spermatogonia are situated close to the testicular theca and produce generally separate primary spermatocytes. From secondary spermatocytes onwards, the nuclear envelope is no longer visible. The spermatids develop synchronously in groups of four, in contrast to arthropod and vertebrate spermatogenesis. A single, large nurse cell, or trophocyte, never observed previously, surrounds each spermatid; perhaps it represents an altered germ cell functioning in nutrition. The spermatid nucleus, initially ovoid, lengthens and takes on the shape of a mushroom head extending into a stalk. Three degrees of chromatin condensation are visible. Anteriorly, a palisade-shaped structure is present just over the highly heterochromatic nuclear zone and is considered to have an acrosome-like function. The outer sperm cytoplasm is characterized by a peripheral tubular labyrinth. Axonemal structures have never been found, but centriole-like structures are present among the medium-density chromatinic strands of the mushroom-like nucleus. No cortical microtubules are evident beneath the cell membrane. The external sperm morphology recalls that of nematode gametes, and some internal features are also similar. Phylogenetic considerations and hypotheses on sperm locomotion are proposed. J. Morphol. 237:165–176, 1998. © 1998 Wiley-Liss, Inc.     

Brassica napus pollen development during generative cell and sperm cell formation

Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.     

Fine structure of spermatozoa and spermatogenesis ofSchizomus palaciosi,Reddell and Cokendolpher, 1986 (Arachnida: Uropygi,Schizomida)

Summary Spermatogenesis ofSchizomus palaciosi occurs in cysts in paired tubular testes located ventrally in the opisthosoma. Only few germ cells comprise one cyst. In early spermiogenesis an acrosomal complex composed of a spherical vacuole and a short acrosomal filament is established opposite of which a 9×2+3 flagellum emerges from a flagellar tunnel. The latter, however, is only a short-lasting structure. A manchette of microtubules surrounds nucleus and part of the acrosomal vacuole. The alterations in the arrangement of the microtubules during spermiogenesis are described. The spermatid finally is an elongate cell with a slender acrosomal vacuole on top of the helical nucleus. A deep implantation fossa filled with dense material is encountered. The acrosomal vacuole is accompanied by an intricate paracrosomal lattice structure not known at present of otherArachnida. This structure disappears during final spermiogenesis. The acrosomal filament (perforatorium) reveals filamentous subunits arranged in a regular pattern. Large ovoid mitochondria do not establish a distinct middle piece. Finally the elongate spermatid is coiled to form the mature spherical spermatozoon.The results are discussed under functional and taxonomical aspects.     

Spermiogenesis and sperm ultrastructure in Cylindrostoma fingalianum (Platyhelminthes,Prolecithophora) with notes on a protozoan (kinetoplastid) symbiont closely associated with allosperm

Summary

The only positive synapomorphy uniting members of the platyhelminth turbellarian taxon, Prolecithophora, is a peculiar membranous system present in much of the shaft of the sperm. This investigation followed the development of this membrane system during spermiogenesis in Cylindrostoma fingalianum and its appearance in the mature sperm. Formation begins with invaginations of the early spermatid shaft outer cell membrane. The invaginations enlarge and the membrane becomes increasingly folded. They appear to be subsequently supplemented with membranous material supplied by an extensive vacuolar system originating from the Golgi apparatus in the main cytoplasmic mass of the spermatid. Throughout development, and in mature sperm, the membranous system forms a part of the outer cell membrane and is also intimately associated with the elongate mitochondrion that lies between the membranous column and the nucleus. The nucleus is highly lobed and the sperm cell lacks flagella or axonemes or the dense bodies found in most other turbellarian taxonomic divisions. A kinetoplastid protozoon present in considerable numbers amongst allosperm is also described.     

Electron microscopic study of spermatogenesis in the lung fluke (Paragonimus miyazakii)

Summary The characteristics of spermatogenesis in a type of pulmonary parasite, Paragonimus miyazakii have been observed using the electron microscope. Groups of several spermatocytes revealed mutual cytoplasmic connection. That degree of this fusion increased as spermatogenesis progressed, and finally developed into a so-called cytophore. Then, this cytophore remained joined with a spermatid by a short stalk until the spermatid changed into a sperm. The nucleus of the spermatid became elongated with a string-like arrangement of the chromatin, which, in turn, showed increased electron density. At the pole of the spermatid, linearly arranged microtubules developed just below the plasma membrane. Close to an elongated portion at the pole, two separate flagella start growing and later fuse with the sperm itself. In the sperm tail a couple of tail filament complexes, longitudinally oriented slender mitochondria, and a tubular structure were present.     

Spermiogenesis and sperm structure in the crabUca tangeri (Crustacea,Brachyura), with special reference to the acrosome differentiation

Summary Early spermatids of the crabUca tangeri consists of the nucleus of granular chromatin and the cytoplasm, which contains a proacrosomal vesicle in close association with membrane lamellae. In the mid spermatids an invagination of the acrosomal vesicle membrane gives rise to the formation of the perforatorium, a spindle-shaped tubule which encloses tubular membranous structures. The pair of centrioles located at the base of the acrosome is not directly involved in perforatorial differentiation. The acrosomal vesicle shows a heterogeneous content composed of the operculum, the thickened ring, and three layers of different materials concentrically arranged around the perforatorium. During the late spermatid stage the nuclear profile differentiates numerous slender arms and the chromatin arranges into fibers. Membranous tubules from the cytoplasm become incorporated into the tubular structures of the perforatorium. The mature spermatozoon has the typical structure of the branchyuran sperm, with a complex acrosome, cupped by the nucleus, and a thin cytoplasmic band intervening between the former main elements. The centrioles are degenerate. The nuclear arms are unusually numerous (more than 20) and lack microtubules or microtubular derivatives.     

Transition of basic protein during spermatogenesis of <Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis> (Osbeck, 1765)

According to the ultrastructural characteristic observation of the developing male germ cells, spermatogenesis of the crustacean shrimp, Fenneropenaeus chinensis, is classified into spermatogonia, primary spermatocytes, secondary spermatocyte, four stages of spermatids, and mature sperm. The basic protein transition during its spermatogenesis is studied by transmission electron microscopy of ammoniacal silver reaction and immunoelectron microscopical distribution of acetylated histone H4. The results show that basic protein synthesized in cytoplasm of spermatogonia is transferred into the nucleus with deposition on new duplicated DNA. In the spermatocyte stage, some nuclear basic protein combined with RNP is transferred into the cytoplasm and is involved in forming the cytoplasmic vesicle clumps. In the early spermatid, most of the basic protein synthesized in the new spermatid cytoplasm is transferred into the nucleus, and the chromatin condensed gradually, and the rest is shifted into the pre-acrosomal vacuole. In the middle spermatid, the nuclear basic protein linked with DNA is acetylated and transferred into the proacrosomal vacuole and assembled into the acrosomal blastema. At the late spermatid, almost all of the basic protein in the nucleus has been removed into the acrosome. During the stage from late spermatid to mature sperm, some de novo basic proteins synthesized in the cytoplasm belt transfer into the nucleus without a membrane and almost all deposit in the periphery to form a supercoating. The remnant histone H4 accompanied by chromatin fibers is acetylated in the center of the nucleus, leading to relaxed DNA and activated genes making the nucleus non-condensed.     

Ultrastructural study of spermatogenesis in silver salmon Oncorhynchus kisutch and cherry salmon O. masou (Salmonidae, Teleostei)

Spermatogenesis in silver salmon Oncorhynchus kisutch and cherry salmon O. masou was studied by transmission electron microscopy. The spermatogenic cells of both species have been shown to have no considerable differences in their dimensional and ultrastructural parameters. The characteristic peculiarity of spermatogonia was the presence of a germ determinant substance, which is the cytoplasmic marker of sex line cells. The primary and secondary spermatocytes, as well as early spermatids, were arranged in gonads as cell clusters at the same stage of development. In spermiogenesis, the regular appearance of the electron-lucent vesicle was observed, which forms a structural complex with the apical condensation of the nuclear membrane. This complex is morphologically similar to the not-yet-formed spermatid acrosomes in many Metazoa and is referred to by the authors as an acrosome-like structure (AS). At the final stage of spermiogenesis, the disappearance of an AS allows one to considering it to be a temporarily existing structure that recapitulates the ancestral morphotype of salmonid sperm. Spermatozoa of the both species are typical, primitive, acrosome-lacking cells, which are characteristic of many representatives of Teleostei that have external insemination.     

Ultrastructure of spermiogenesis of Philippia (Psilaxis) oxytropis,with special reference to the taxonomic position of the architectonicidae (Gastropoda)

Summary Spermiogenesis of the architectonicid Philippia (Psilaxis) oxytropis was studied using transmission electron microscopy. Both spermatids and mature sperm of Philippia show features comparable to sperm/spermatids of euthyneuran gastropods (opisthobranchs, pulmonates) and not mesogastropods (with which the Architectonicidae are commonly grouped). These features include: (1) Accumulation of dense material on the outer membrane of anterior of the early spermatid nucleus — this material probably incorporated into the acrosome; (2) Structure of the unattached and attached spermatid acrosome (apical vesicle, acrosomal pedestal) accompanied by curved (transient) support structures; (3) Formation of the midpiece by individual mitochondrial wrapping around the axonemal complex, and the subsequent fusion and metamorphosis of the mitochondria to form the midpiece; (4) Presence of periodically banded coarse fibres surrounding the axonemal doublets and intra-axonemal rows of granules. A glycogen piece occurs posterior to the midpiece but is a feature observed in both euspermatozoa of mesogastropods (and neogastropods) and in sperm of some euthyneurans.Despite the lack of paracrystalline material or glycogen helices within the midpiece (both usually associated with sperm of euthyneurans), the features of spermiogenesis and sperm listed indicate that the Architectonicidae may be more appropriately referable to the Euthyneura than the Prosobranchia.Abbreviations a acrosome - ap anterior region of acrosomal pedestal - as support structures of spermatid acrosome - av apical vesicle of acrosome (acrosomal vesicle of un-attached acrosome) - ax axoneme - b basal region of acrosomal pedestal - c centriole - cf coarse fibres - cr cristal derivative of midpiece - db intra-axonemal dense granules - drs dense ring structure - gg glycogen granules - gp glycogen piece - G Golgi complex - m mitochondrion - mt microtubules - n nucleus - pm plasma membrane - sGv small Golgi vesicles     

A transmission electron microscopy investigation: the membrane complex in spermatogenesis of <Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis>

The transforming characteristics of the membrane complex in spermatogenesis of Fenneropenaeus chinensis have been studied by using transmission electron microscopy. Two types of membrane complex have been investigated based on their sources: one originating from nucleus and the other from cytoplasm. The first one, consisted of annular structures, monolayer membrane blebs, and double or multi-lamellar membrane vesicles, emerges in the primary spermatocyte, then diffuses with the nuclear membrane and finally enters the cytoplasm. This type of membrane complex seems to play an important role in the materials transfusion from nucleus to cytoplasm, and it mainly exists inside the primary spermatocyte with some inside the secondary spermatocyte. The latter, originated from cytoplasm, is formed during the anaphase of spermiogenesis. It also exists in mature sperm, locating at both sides of the nucleus under the acrosomal cap. This type of membrane complex mainly comprises rings of convoluted membrane pouches, together with mitochondria, annular lamina bodies, fragments of endoplasmic reticulum, nuclear membrane and some nuclear particles. It releases vesicles and particles into the acrosomal area during the formation of the perforatorium, suggesting a combined function of the endoplasmic reticulum, mitochondria and Golgi’s mechanism.     

STUDIES OF SPERMIOGENESIS IN A NEMATODE, NIPPOSTRONGYLUS BRASILIENSIS

The fine structure of the developing spermatids and the mature sperm of Nippostrongylus brasiliensis was investigated. Immature spermatids are found at one end of the tubelike testis, and the mature sperm at the other. The spermatid has a prominent nucleus, with the chromatin clumped at the margin. It also contains a pair of centrioles, located near the nucleus. The cytoplasm is filled with ribosomal clusters, but it lacks an organized Golgi area or endoplasmic reticulum. Besides the normal mitochondria, the spermatid has specialized mitochondrionlike inclusions with dense matrix, few broad cristae, and a crystalloid structure always facing the nucleus. As spermiogenesis proceeds, the nucleus elongates, comes to lie at one end, and later evaginates to form a separate head structure, leaving the mitochondria and other cytoplasmic organelles in a broad cytoplasmic region. The nuclear material becomes filamentous and spiral, and the centrioles come to lie at one end near the junction of the head and the cytoplasmic portion of the sperm. Microtubules are found in the cytoplasmic region extending from the tubelike nucleus. The specialized mitochondria are about eighteen in number, and are arranged in rows in staggered groups of three around the microtubules in the cytoplasmic region. The mature sperm is aflagellate and lacks an acrosome. No movement of the sperm was ever observed.     

Spermatogenesis and sperm structure of Acerella muscorum, (Ionescu, 1930) (Hexapoda, Protura)

The general organization of the male genital system, the spermatogenesis and the sperm structure of the proturan Acerella muscorum have been described. At the apex of testis apical huge cells are present; their cytoplasm contains a conventional centriole, a large amount of dense material and several less electron-dense masses surrounded by mitochondria. Spermatocytes have normal centrioles and are interconnected by cytoplasmic bridges. Such bridges seem to be absent between spermatid cells and justify the lack of synchronization of cell maturation. Spermatids are almost globular cells with a spheroidal nucleus and a large mass of dense material corresponding to the centriole adjunct. Within this mass a centriole is preserved. Mitochondria of normal structure are located between the nucleus and the plasma membrane. The spermatids are surrounded by a thick membrane. No flagellar structure is formed. Sperm have a compact spheroidal nucleus, a large cap of centriole adjunct material within which a centriole is still visible. A layer of mitochondria is located over the nucleus. The cytoplasm is reduced in comparison to spermatids; many dense bodies are interspersed with sperm in the testicular lumen. The sperm are small, immotile cells of about 2.5-3 μm in diameter.     

The axoneme is involved in the elongation of the spermatid nucleus of Drosophila subobscura

Summary

Our analysis of spermiogenesis of Drosophila subobscura indicates that the axoneme takes part in the elongation of the spermatid nucleus, as follows. In sperm of D. subobscura the axoneme accompanies the nucleus in its full length up to the acrosome. Before the elongation of the nucleus begins, the centriole contacts the nuclear membrane, and is orientated with its axis to the centre of the spherical nucleus. Later in development, at the beginning of nucleus elongation, the axis of the centriole does no longer point to the centre of the nucleus but is dislocated more to one side of the nucleus. Subsequently, the axoneme which is growing from the centriole, pushes the nucleus which develops a cap-like structure over the anterior end of the centriole. By the continuosly growing axoneme stretching forces are applied to the anterior part of the nucleus. Consequently the elongating nucleus gets a smaller diameter anteriorly than posteriorly. And the longer the total length of the sperm is the longer is the nucleus. During elongation the chromatin shows a network-like structure. Nucleus elongation stops when the chromatin is fully condensed but the axoneme continues to grow. Thereupon the cap is no longer seen, and the anterior part of the nucleus which previously was the cap, forms now a bulge beside the centriole and the axoneme.     

A comparative study on the fine structure of developing spermatozoa in the isopod,Oniscus asellus,and the amphipod,Orchestoidea sp.

Summary Developing spermatids and mature spermatozoa from the isopod, Oniscus asellus and the amphipod, Orchestoidea sp. have been examined with the light microscope and the electron microscope and have been found to have similar morphologies. As spermiogenesis proceeds the nucleus migrates to one pole of the spermatid at which point an acrosome, contiguous rod, and cross-striated tail develop. The acrosomal vesicle elongates to a cone-shaped, mature acrosome lying at the apex of a cross-striated tail and nucleus which are situated at approximate forty-five degrees to each other. The cross-striated tail originates as an evagination of the spermatid plasma membrane near the acrosomal vesicle. The tail eventually grows to lengths of four to five hundred microns. The mature, tail-like appendage is cross-striated at major 750 to 800 Å, and minor 125 to 150 Å, periodicities. When observed in vitro, mature sperm of both species appear non-motile.Possible homologies of this unusual spermatozoon with other types of spermatozoa are made and it is concluded that: 1) isopod and amphipod spermatozoa should be classified as non-flagellate; 2) the cross-striated tail, previously thought to be a flagellum, is a non-motile structure associated in development and possible function with the acrosome; and 3) the rodlike structure contiguous with the acrosome is similar to perforatoria described in some vertebrate sperm.Supported by U.S.P.H.S. Grant No. NB-06285 and Training Grant No. 5-Tl-GM-202. — The author wishes to express his grateful appreciation for the technical assistance given by Miss Ann Barnett during the course of this investigation.     

Nuclear and cytoplasmic differentiation in developing sperm of the crayfish,Cambaroides japonicus

Summary In the present electron microscopic study of spermatogenesis in the crayfish, Cambaroides japonicus, it was possible to clarify several aspects of the unusual differentiation which leads to the production of an aflagellate sperm. The centriole is followed from the metaphase of the second spermatocyte division to the time at which, in the nearly mature sperm, it appears to disintegrate. It has no connection with the acrosome but in the late spermatid and maturing sperm it is found randomly oriented among the convoluted membranes of the filamentous endoplasmic reticulum.There appears to be a close association of mitochondria with the developing acrosomal vesicle. Typical mitochondria, however, are not present after the late spermatid stage of development. It is suggested that the complex lamellar bodies associated with the nuclear envelope in the late stages of spermatogenesis may be related to mitochondria for these lamellar bodies resemble the complex mitochondria found in the adjacent nutritive cells.The development of the acrosome has been traced from an aggregate of dense granules which first appear in the interzonal spindle region and are later segregated at one side of the cell after the second spermatocyte division. As differentiation proceeds, tubular elements appear and disappear within the acrosome, while somewhat later, fibrous elements appear in the matrix. In the mature acrosome, the fibrous elements remain only adjacent to the granular periphery of the acrosome and the core again becomes homogeneous.No typical Golgi complex is found in these cells at any time during their differentiation.In the maturing sperm the development of the arms of the nucleus was studied. Preceding the differentiation of the arms a coarse fibrous material develops in the periphery of the nucleus. It is shown that the fibrillar material in the matrix of the arms is in continuity with the fibrillar material in the matrix of the nucleus proper.Supported in part by Grant No. B 2314 of the National Institute of Neurological Diseases and Blindness, U.S. Public Health Service.Predoctoral Research Fellow of the National Institute of Neurological Diseases and Blindness, U.S. Public Health Service.     

Characterization and expression analysis of <Emphasis Type="Italic">prohibitin</Emphasis> in the testis of Chinese mitten crab <Emphasis Type="Italic">Eriocheir sinensis</Emphasis>

Prohibitin plays a key role in maintaining mitochondrial membrane integrity and retaining its normal function. We have initially cloned and sequenced the cDNA of prohibitin from testis of the crab Eriocheir sinensis. The 1,357 bp Prohibitin cDNA comprises a 105 bp 5′ untranslated region, a 427 bp 3′ untranslated region and a 825 bp open reading frame. Protein alignment substantiates that the Prohibitin has 70.2, 69.8, 70.5, 70.9, 72.4, 70.6 and 74.9% identity with its homologues in Mus musculus, Homo sapiens, Gallus gallus, Danio rerio, Xenopus tropicalis, Drosophila mojavensis and Aedes aegypti, respectively. In situ hybridization revealed that the Prohibitin mRNA was mainly localized around the proacrosomal vesicle and nucleus membrane in early-stage spermatid. In the following middle stage, Prohibitin mRNA was situated inside the invaginated region of half-moon-like nucleus and surrounded the proacrosomal vesicle. In late-stage spermatid, the mRNA was aggregated in the acrosomal tubule, the band between the acrosome and cup-like nucleus, remanent cytoplasm as well. In the mature sperm, mRNA was only found in the acrosomal tubule and the limited space between the nucleus and acrosome. Therefore, we presume that Prohibitin may fulfill critical functions in the spermiogenesis of Eriocheir sinensis.