Sperm structure and spermiogenesis in Coletinia sp. (Nicoletiidae, Zygentoma, Insecta) with a comparative analysis of sperm structure in Zygentoma

The spermatozoon of Coletinia sp. has a bilayered acrosome, a short nucleus (4 microm) and a relatively short sperm tail with two mitochondrial derivatives. The chromatin is uniformly dense except for several electron-lucid channels or strands which permeate the nucleus and which originate in the spermatid as invaginations of the nuclear envelope. The invaginations occur mostly or exclusively along two meridians of the spermatid that are also characterized by the presence of a longitudinal rod of medium electron density. The two rods (designated as 'mid-spermatid rods') evidently are instrumental in the formation of the electron-lucid channels. The significance of this elaborate system of intranuclear channels is not understood. The sperm tail has a 9 + 9 + 2 axoneme with each of the nine microtubular doublets accompanied by an accessory microtubule; scant intertubular material can also be distinguished. Hence, the tail axoneme resembles that of many pterygote insects. Each of the two mitochondrial derivatives contains a crystalline inclusion that has periodically spaced layers going in different directions on either side of the midline. Two synapomorphic traits appear to be shared by Ateluridae and Nicoletiidae, namely the invaginations of the nuclear membrane along two meridians of the nucleus and the shape of the crystalline inclusions of the mitochondrial derivatives. Four species from the family Lepismatidae were also examined as to their sperm ultrastructure. Three of them, Allacrotelsa kraepelini, Ctenolepisma longicaudata and Ctenolepisma sp., were found to be very similar to the two previously examined lepismatids, Thermobia domestica and Lepisma saccharina. On the other hand, spermatozoa of Tricholepisma aurea were aggregated in small groups rather than pairwise joined as seen in the other lepismatids. Sperm characters are also used to reconstruct a phylogenetic hypothesis which suggests a close relationship between Ateluridae and Nicoletiidae.     

Axoneme-dependent tubulin modifications in singlet microtubules of the Drosophila sperm tail

Drosophila melanogaster sperm tubulins are posttranslationally glutamylated and glycylated. We show here that axonemes are the substrate for these tubulin C-terminal modifications. Axoneme architecture is required, but full length, motile axonemes are not necessary. Tubulin glutamylation occurs during or shortly after assembly into the axoneme; only glutamylated tubulins are glycylated. Tubulins in other testis microtubules are not modified. Only a small subset of total Drosophila sperm axoneme tubulins have these modifications. Biochemical fractionation of Drosophila sperm showed that central pair and accessory microtubules have the majority of poly-modified tubulins, whereas doublet microtubules have only small amounts of mono- and oligo-modified tubulins. Glutamylation patterns for different beta-tubulins experimentally assembled into axonemes were consistent with utilization of modification sites corresponding to those identified in other organisms, but surrounding sequence context was also important. We compared tubulin modifications in the 9 + 9 + 2 insect sperm tail axonemes of Drosophila with the canonical 9 + 2 axonemes of sperm of the sea urchin Lytichinus pictus and the 9 + 0 motile sperm axonemes of the eel Anguilla japonica. In contrast to Drosophila sperm, L. pictus sperm have equivalent levels of modified tubulins in both doublet and central pair microtubule fractions, whereas the doublets of A. japonica sperm exhibit little glutamylation but extensive glycylation. Tubulin C-terminal modifications are a prevalent feature of motile axonemes, but there is no conserved pattern for placement or amount of these     

Comparative spermatology in Plecoptera (Insecta): an ultrastructural investigation on four species

The ultrastructure of spermatozoa of four Plecoptera species, Leuctra fusca Linnaeus, Brachyptera risi (Morton), Taeniopteryx stankovitchi Ikonomov, T. kuehtreiberi (Aubert), was investigated by light microscopy, scanning and transmission electron microscopy, and immunofluorescence microscopy. The spermatozoa of all the species have a complex acrosome, are filiform and flagellate, with a '9+9+2' axoneme flanked by two mitochondrial derivatives. However, the structure shows a certain interspecific heterogeneity. L. fusca has a short conical nucleus in the apical position and an axoneme flanked by two accessory bodies. In the sperm of the Taeniopterygidae, the nucleus is a long cylindrical body which lies between the two mitochondrial derivatives flanking the axoneme for most of its length. Our results suggest a close phylogenetic affinity between Plecoptera and the other orders of Polyneoptera, although the proposed sister-group relationship between Plecoptera and Embioptera cannot be confirmed.     

New findings on sperm ultrastructure of Xenos vesparum (Rossi) (Strepsiptera,Insecta)

The systematic position of insect order Strepsiptera is still under debate. It was, therefore, thought of interest to examine the ultrastructure of a strepsipteran in a search for synapomorphies shared with Coleoptera, Diptera, or any other insect order. The fine structure of spermatozoa and the spermatid from Xenos vesparum (Rossi) was re-examined using scanning and transmission electron microscopy and a fixation technique that permits the visualization of the macromolecular organization of the organelles. The spermatozoon was shown to possess several traits that are characteristics of insects in general, such as a 9 + 9 + 2 axoneme, two mitochondrial derivatives containing a crystalline material and two 'zipper lines' present along the sperm tail. Seventeen protofilaments occurred along most of the accessory tubules, which reduced to 16 posteriorly. An acrosome is absent. The neck region contains a prominent centriolar adjunct, which gives rise to two accessory bodies which adhere to the mitochondrial derivatives, and to slender strands of the so-called intertubular material found between the accessory tubules. Of interest is the finding that the glycocalyx consists of prominent filamentous strands, similar to those found in siphonapterans, mecopterans and basal dipterans.     

Sperm ultrastructure in Chironomoidea (Insecta, Diptera)

The fine structure of spermatozoa from several species of chironomids, of Culicoides sp. (Ceratopogonidae) and of Odagmia pontina (Simulidae) was studied. A synapomorphic feature, consisting of nine kidney-shaped structures forming the centriole adjunct, was found in the chironomid species. All members of Chironomoidea share a mono-layered acrosome and a flagellar axoneme, provided with accessory tubules with 15 protofilaments in their tubular wall. The axoneme has a 9+9+2 pattern, but in an unidentified species of chironomid, a 9+9+0 model was observed where the central complex and the spokes are missing. Sperm motility is, however, maintained in all the examined species. The spermatozoa of this taxon have the tendency to complete maturation during their progression along the deferent ducts. Thus, in the proximal region of these ducts, they often show remnants of the spermatid cytoplasm.     

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.     

Structure and energy pathways of spermatozoa of the rove beetle Aleochara bilineata (Coleoptera, Staphylinidae)

The morphology of mature spermatozoa of the rove beetle Aleochara bilineata was examined by using scanning and transmission electron microscopy. They are about 1000 mum long and filiform. The acrosome and the nucleus are elongate and each about 20 mum long. A well-developed centriole adjunct region connects the nucleus with the sperm tail. The axoneme reveals the 9 + 9 + 2 pattern of the pterygote sperm flagellum. Two accessory bodies and two mitochondrial derivatives with paracrystalline inclusions are present. Cristae are reduced to the cortical zone of the derivatives. Cytochrome-c oxidase activity was detected within the cristae by DAB-reaction. The energy metabolism of the spermatozoa was investigated by using different inhibitors affecting the mitochondrial and cytoplasmic metabolic pathways. Sperm movement was used as an indicator for the utilization of ATP by the axoneme. In control experiments, the duration of motility was longer than 45 min. In the presence of atractyloside or potassium cyanide the motility duration was not affected. On the other hand, iodoacetic acid in the medium stopped sperm motility within 15 min. This indicates that sperm energy metabolism mainly depends on the glycolytic pathway.     

Sperm ultrastructure and spermiogenesis of Coniopterygidae (Neuroptera, Insecta)

The spermiogenesis and the sperm ultrastructure of several species of Coniopterygidae have been examined. The spermatozoa consist of a three-layered acrosome, an elongated elliptical nucleus, a long flagellum provided with a 9+9+3 axoneme and two mitochondrial derivatives. No accessory bodies were observed. The axoneme exhibits accessory microtubules provided with 13, rather than 16, protofilaments in their tubular wall; the intertubular material is reduced and distributed differently from that observed in other Neuropterida. Sperm axoneme organization supports the isolated position of the family previously proposed on the basis of morphological data.     

Spermatogenesis and ultrastructure of the spermatozoa of Seison nebaliae (Syndermata)

 The spermatozoa of Seison nebaliae are characterized by an elongated sperm body, a filiform nucleus, and an anteriorly inserting external cilium with a 9×2+2 axoneme pattern. In the sperm body a frontal, middle, and hind region can be distinguished. The frontal region contains an acrosomal vesicle, a perforatorium, a basal body, and a pair of apical dense bodies; an accessory centriole is absent. The middle region is characterized by several so-called filamental plates. One large mitochondrion and one pair of accessory tubular structures are located in the middle and hind region. The hind region also contains two rows of dense bodies. Accessory tubular structures and filamental plates are autapomorphies of S. nebaliae. The shared appearance of the dense bodies in spermatozoa of species of the taxa Seison and the Acanthocephala founds their sister-group relationship, while the anterior insertion of the cilium in the spermatozoa of these taxa and in the Rotifera confirms the monophylum Syndermata Ahlrichs, 1995. Accepted: 5 August 1998     

Flagellar Axonemes with 10 Microtubular Doublets in Spermatozoa from Gall-midges (Diptera,Cecidomyiidae)

Abstract The spermatozoa of some gall-midges (Cecidomyiidae, Lestremiinae), belonging to the tribe Micromyini, were seen to have an axoneme that consists of 10, instead of nine, microtubular doublets surrounding a central cylinder. In some related species within the same tribe the axoneme was found to contain a similar cylinder but to have nine doublets, as in typical flagella, or to have nine doublets and no central structure. These three types of axonemes can be given the shorthand designations “10+cyl”,“9+cyl”, and “9+0”. The tribe Lestremiini is characterized by a giant axoneme having 150 doublets in two rows reversely oriented. Other characteristics of examined spermatozoa are the electron density of the B-tubules of the axoneme, a feature shared by all members of the subfamily Lestremiinae, and the presence of a prominent cytoplasmic droplet containing numerous, regularly spaced microtubules, which is shared by all Micromyidi. These axonemal models are discussed from a phylogenetic point of view.     

Structure and function of the spermathecal complex in the phlebotomine sandflyPhlebotomus papatasi Scopoli (Diptera: Psychodidae): II. Post-copulatory histophysiological changes during the gonotrophic cycle

The spermathecal complex ofPhlebotomus papatasi Scopoli (Diptera: Psychodidae) undergoes histological and physiological changes during its gonotropic cycle. The present histochemical study revealed a mucopolysaccharide secretory mass in the spermathecae of the newly emerged sandfly. Sperm competition occurs when two or more males compete to fertilize an ovum in the female reproductive tract. In this study, spermatophores of two or more competing males were deposited at the base of the spermathecal ducts, which originate from the female bursa copulatrix. This suggests that females play a role in sperm displacement, which is defined as any situation in which the last male to mate with a female fertilizes maximum number her eggs. A blood meal ingested by the female for ovary development and egg laying stimulates the release of sperm from the spermatophore. The spermatozoa then migrate to the lumen of the spermatheca. The ultrastructure of spermatozoa comprises a head with double-layered acrosomal perforatorium, an elongate nucleus, and the axoneme with a 9 + 9 + 0 flagellar pattern. This axomene differs from the aflagellate axoneme of other Psychodinae. Morphological changes, such as the casting off of the acrosomal membrane, and histological changes in the spermatophore are also described. Mating plugs that have been described previously in sandflies appear to be artefacts. Females ofP. papatasi may be inseminated more than once during each gonotrophic cycle, and additional inseminations may be necessary for each cycle. The relationships between the volumes of the sperm and the spermatheca were calculated to determine sperm utilization and fecundity ofP. papatasi. As the females ofP. papatasi mate polyandrously, the anatomical and physiological complexity of the spermathecal complex may be related to post-copulatory sexual selection.     

Ultrastructural characterization of spermatozoa in euglossine bees (Hymenoptera, Apidae, Apinae)

Summary. Euglossine spermatozoa are the longest described to date for the Hymenoptera. This cell includes a head and a flagellar region. In transverse sections, the acrosome is circular at the tip but has an oval contour along most of its length. The perforatorium penetrates into a deep cavity in the nuclear tip. The flagellum consists in an axoneme, a pair of mitochondrial derivatives, a centriolar adjunct and a pair of accessory bodies. The axoneme has a 9+9+2 microtubule pattern which becomes gradually disorganized in the final portion, with the central microtubules and the nine doublets terminating simultaneously, followed by the accessory microtubules. The mitochondrial derivatives are asymmetric both in length and diameter. Sectioned transversally, the derivatives are ellipsoidal or have a pear shape. The larger one has a more obvious paracrystalline region. The centriolar adjunct begins at the nuclear base and extends parallel to the axoneme until it encounters the smaller mitochondrial derivative, on which it fits, making a concave groove. In addition to these consistent euglossine features, species-specific differences that might be useful in phylogenetic work on the group are also noted.Received 18 October 2003; revised 4 September 2004; accepted 4 October 2004.     

Spermatozoa and sperm packages of the European troglophylous scorpion Belisarius xambeui Simon, 1879 (Troglotayosicidae, Scorpiones)

Studies on the sperm morphology in scorpions are rare, but the existing investigations already revealed a remarkable interfamiliar diversity. The present study reports for the first time on the spermatozoa and sperm packages of a representative of the family Troglotayosicidae, the troglophylous species Belisarius xambeui. The spermatozoa are characterized by (1) a thread-like nucleus, which is slightly bent anteriorly; (2) an asymmetrical cap-like acrosomal vacuole, which encloses the anterior tip of the nucleus; an acrosomal filament is absent; (3) an axoneme with a 9 + 0 microtubular pattern; (4) a midpiece consisting of elongated mitochondria coiling around the axoneme; the number can vary between 3 and 6 (mostly 4). At the end of spermiogenesis, the spermatozoa aggregate in order to form oval-shaped sperm packages in which all sperm cells show the same orientation. A single package consists of approximately 150 sperms. A secretion sheath is always absent. The present results might provide new characters for further systematic studies and their phylogenetic implications are briefly discussed.     

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.     

ULTRASTRUCTURE OF THE FLAGELLUM IN SPERM OF CKCINELLA SEPTEMPUNCTATA

Abstract  Using cell whole mount preparation and ultrathin section technique, the ultrastructure of the flagellum in the sperm of Coccinella septempunctata L. was examined with transmission electron microscope. The flagellum is made up of a classic 9+9+2 axoneme containing two similar crystallized mitochondria1 derivatives, two accessory bodies, which are divided in to two portions, an osmiophilic dense crescent and a spongy one, and a non-crystalline body. At the end of the flagellum, only the axoneme is present, it loses the two central microtubules but retains the nine doublets with dynein arms and the nine accessory microtubules.     

The sperm structure of Cryptocercus punctulatus Scudder (Blattodea) and sperm evolution in Dictyoptera

Sperm of the dictyopteran key taxon Cryptocercus punctulatus was examined. It has largely maintained a blattodean groundplan condition, with a three‐layered acrosome, an elongate nucleus, a single centriole, a conspicuous centriole adjunct material, two connecting bands (=accessory bodies), and a long functional flagellum with a 9+9+2 axoneme provided with accessory tubules with 16 protofilaments and intertubular material. These sperm characters are shared with several other polyneopterans. The sperm of C. punctulatus is very similar to what is found in Periplaneta americana and species of other groups of roaches, including the sperm of Loboptera decipiens described here for the first time. The general sperm organization here described can be assumed for the groundplan of Insecta and Pterygota. The following evolutionary path can be suggested: after the split between Cryptocercidae and the common ancestor of Isoptera, the typical pattern of sperm formation was altered very distinctly, resulting in a duplication or multiplication (Mastotermitidae) of the centrioles. Mastotermes has maintained a certain sperm motility, but with a very unusual apparatus of multiple flagella with a 9+0 axoneme pattern. After the split into Mastotermitidae and the remaining Isoptera, sperm motility was completely abandoned, and different modifications of sperm components occurred, and even the loss of the sperm flagellum. J. Morphol. 276:361–369, 2015. © 2014 Wiley Periodicals, Inc.     

Ultrastructure and motility pattern of the spermatozoa of Aleochara curtula (Coleoptera, Staphylinidae)

Ultrastructure and motility pattern of spermatozoa of the rove beetle Aleochara curtula were examined using electron and light microscopic methods. The spermatozoon is about 100 microm long and filiform. The head piece comprises a 5 microm long triple layered acrosome and 10 microm long nucleus. The flagellum consists of a 9+9+2 axoneme, two accessory bodies and two mitochondrial derivatives about equal in size but of different shape in their cross sections. In both derivatives there are paracrystalline inclusions. The flagellum is attached to the head by a 2 microm long centriole adjunct which is characterized by its electron dense material that forms a three layered folded lamellar structure. When liberated in buffer solution the sperm flagella assume a coiled hook-like form with the excentric stiff head protruding in front. The spermatozoa are driven through the medium by a small helicoidal wave of high frequency superimposed to the bent flagella. The maximum speed measured was 15.2 microm/s. The sperm architecture of A. curtula is similar to that of other Aleochara species but differs in total length and dimensions of the mitochondrial derivatives. For that reason Aleochara sperm can certainly prove useful to study the effect of the mitochondrial derivatives on sperm motility.     

The short spermatodesm of Arge pagana (Hymenoptera: symphyta)

In the seminal vesicle of the 'symphyta'Arge pagana the spermatozoa are stored in motile spermatodesm bundles, maintained by an anterior cap of extracellular material. This cap consists of a denser cortex and of an internal matrix, where part of the sperm heads are embedded. The number of spermatozoa per bundle is variable. The spermatozoa are short, only 30microm long, with a head region of about 23microm, and a very short flagellum of about 7microm. The head includes the acrosome, with a perforatorium, and the nucleus. The flagellum consists of an axoneme, with a 9+9+2 microtubule pattern, a centriolar adjunct, two mitochondrial derivatives and two accessory bodies. The mitochondrial derivatives are very slender and of different lengths. The longer begins at the base of the nucleus, while the shorter one starts just below the base of the centriolar adjunct. This latter is asymmetric and appears at the nuclear base, extending parallel to the axoneme up to the anterior end of the smaller mitochondrial derivative. The short spermatodesmata and the small mitochondrial derivatives characterize the A. pagana sperm. In addition, the centriolar adjunct asymmetry and the occurrence of spermatodesm bundles might be considered plesiomorphic states present in the basal Tenthredinoidea.     

Morphology of the male reproductive system and sperm ultrastructure of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

The male reproductive tract of Leucoptera coffeella was processed for light and transmission electron microscopy. In the testis, the eupyrene cells are arranged in individual cysts, while the apyrene cysts form aggregates, never observed in other Lepidoptera. Both cysts contain 128 spermatozoa, which differ from the typical pattern. In the seminal vesicle, both types of spermatozoa are dispersed in the lumen, also different from other Lepidoptera. The apyrene spermatozoa are similar to those observed for other Lepidoptera. They present an anterior region covered by a dense cap and the flagellum is composed of a 9 + 9 + 2 axoneme and two mitochondrial derivatives. The eupyrene spermatozoa, however, differ from the typical pattern for Lepidoptera. Their anterior region contains a nucleus, an acrosome and a peculiar arc of eight accessory microtubules connected to the plasma membrane by dense bridges. In the nucleus–flagellum region, the ninth accessory microtubule is assembled between both mitochondrial derivatives, to participate in the axoneme. The flagellum comprises a 9 + 9 + 2 axoneme and two mitochondrial derivatives with paracrystalline cores. External to the plasma membrane and close to the accessory microtubules, there are tufts of an amorphous material, suggesting reduced lacinate appendages, while the reticular ones are absent. The reduction of lacinate appendages and the absence of sperm bundles in the seminal vesicle support the concept that the appendages of other Lepidoptera could be associated with the eupyrene aggregations. The characters ‘number of spermatozoa per cyst’ and ‘absence of bundles’ should be considered plesiomorphic, supporting the position of this taxon in the base of the Ditrysia.