Sperm Bundles in the Seminal Vesicle of the Crematogaster victima (Smith) Adult Males (Hymenoptera: Formicidae)

This study establishes the presence of spermatodesm in the seminal vesicles of sexually mature males of Crematogaster victima (Smith). In this species, the spermatozoa are maintained together by an extracellular matrix in which the acrosomal regions are embedded. This characteristic has not yet been observed in any other Aculeata. However, the sperm morphology in this species is similar to that described for other ants. The spermatozoa measure on average 100 μm in length, and the number of sperm per bundle is up to 256. They are composed of a head formed by the acrosome and nucleus; this is followed by the flagellum, which is formed by the centriolar adjunct, an axoneme with a 9?+?9?+?2 microtubule pattern, two mitochondrial derivatives, and two accessory bodies. The acrosome is formed by the acrosomal vesicle and perforatorium. The nucleus is filled with compact chromatin with many areas of thick and non-compacted filaments. Both mitochondrial derivatives have the same shape and diameters. The presence of sperm bundles in sexually mature males differentiates C. victima from other ants; however, the similarities in the sperm ultrastructure support the monophyly of this insect group.     

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.     

The spermatozoon of Mengenilla moldrzyki (Strepsiptera,Mengenillidae): Ultrastructure and phylogenetic considerations

Even though the spermatozoa of several strepsipteran species were described earlier, no data were available for the basal family Mengenillidae. Well-fixed material of the recently described Tunisian species Mengenilla moldrzyki was used for a detailed examination of the sperm ultrastructure. The total length is c. 30 μm. The head region contains a conical acrosome vesicle (0.3-0.35 μm) and an elongated nucleus (7.3 μm) with dense chromatin. Some granular material along with a uniformely dense centriole adjunct and two mitochondrial derivatives are visible at the posterior end of the nucleus. The material of the centriole adjunct does not extend along the flagellum and accessory bodies are absent. The mitochondrial derivatives are elongated structures crossed by a longitudinal crista but lacking parallel transverse cristae and paracrystalline material in the dense matrix. The mitochondrial derivatives gradually reduce their size and end at the most posterior tail region. The flagellar axoneme has a 9 + 9 + 2 pattern and originates beneath the nucleus. In the terminal tail region the axoneme gradually disintegrates. Despite the extreme specialization of the endoparasitc group, strepsipteran spermatozoa are mostly characterized by plesiomorphies. The pattern within the order is largely uniform, but Mengenilla displays several apomorphic features compared to the presumptive strepsipteran groundplan (e.g., absence of crystallizations and cristae in the mitochondrial derivatives). The subdivision of the intertubular material into two compartments with a dense beak-like structure adhering to the tubular wall supports a clade Coleopterida (=Strepsiptera + Coleoptera) + Neuropterida.     

The length of a short sperm: Elongation and shortening during spermiogenesis in Cotesia congregata (Hymenoptera,Braconidae)

The spermatozoon of the parasitoid wasp Cotesia congregata is an extremely short gamete measuring less than 7 μm; it is as yet the shortest flagellated sperm to be identified. The mature sperm consists of an acrosome, surrounded by an extra cellular coat, a condensed nucleus, two uncoiled mitochondrial derivatives and a short axoneme. Testes of young adults contain a continuum of differentiation stages. Initially, the flagellum is approximately 5 μm long. It conserves its length in round, elongated and mature spermatids, but is reduced to less than 3 μm in mature spermatozoa. The nucleus is 2 μm in diameter when round, 10 μm long when it becomes a long boat-hull shaped filament, and then reduces to 3.6 μm. Thus, during development the gamete reaches a total length of 15 μm before finally reducing to less than half that length. Some traits of mature sperm anatomy are similar to related species of the Braconidae family, but others seem to be specific and could be due to the shortness of the cell. This uncommon elongation and subsequent shortening of such a tiny flagellated cell constitutes a model for both nucleus and cilium development.     

Polymorphism of spermatozoa in Largus rufipennis Laporte 1832 (Heteroptera: Pyrrhocoroidea: Largidae)

The production of polymorphic spermatozoa has been registered in various insect orders such as Diptera, Lepidoptera, and Hemiptera. In this work, morphology of two types of spermatozoa produced by Largus rufipennis was reported for the first time in the Largidae family. For this, techniques including optical and transmission electron microscopy were used. Spermatozoa measured, on the average, 260 and 200 μm, and both types possessed a nucleus measuring on the average 65 μm. No ultrastructural differences were observed between the two spermatozoa types from L. rufipennis. The head region is composed of an acrosome, a nucleus, and part of the centriolar adjunct. The centriolar adjunct is in parallel with the nucleus and followed by mitochondrial derivates. The flagellum consists of an axoneme (9 + 9 + 2 microtubules) and two mitochondrial derivatives; no other accessory bodies were observed. The mitochondrial derivatives are symmetric in size and diameter. A similar quantity of the two spermatozoa types was observed in the seminal vesicle (57% of the large type and 43% of the small type), while in the spermatheca of the female, the larger spermatozoa were preferentially stored (87%). These results permit discussions concerning of the species biology reproduction, most specifically sperm competition strategies.     

Testicular,spermatogenesis and sperm morphology in Martarega bentoi (Heteroptera: Notonectidae)

The testicular, spermatogenesis and sperm morphology of the backswimmer Martarega bentoi was described using light and transmission electron microscopy. In this species, a pair of testes, two deferent ducts, two different pairs of accessory glands, and an ejaculatory duct form the male reproductive system. Each testis consists of two testicular follicles, which are arranged side by side in snail shape. The follicles are filled with cysts at different stages of spermatogenesis, but in the same cyst the germ cells (up to 64) are in the same stage. At the end of spermatogenesis, the sperm cells are very long, with the flagellum measuring approximately 2500 μm in length, the nucleus only 19 μm, and the acrosome, with two distinct regions, 300 μm. The flagellum is composed of an axoneme, with a 9 + 9 + 2 microtubular pattern, and 2 asymmetric mitochondrial derivatives (MDs). These have the anterior ends inserted into two cavities at the nucleus base, exhibit two paracrystalline inclusions, and have bridges linking them to the axoneme. Few spermatozoa per cyst, asymmetry in size and shape of the MDs, as well as their insertion at the nuclear base are characteristics considered derived, and that differentiate the sperm of M. bentoi from those of the Nepomorpha, Belostomatidae and Nepidae.     

Sperm morphology of the Prorops nasuta (Waterston, 1923) (Hymenoptera: Bethylidae)

In the present study, spermatozoa of the Prorops nasuta (Hymenoptera: Bethylidae) parasitoid were described morphologically. This is the first publication to describe a species belonging to the superfamily Chrysidoidea. Light and transmission electron microscopy were used. The spermatozoa of P. nasuta are linear, with a mean length of 665 μm. The acrosome is composed of an acrosomal vesicle and a perforatorium. The nucleus measures approximately 17 μm in length and is circular at its cross-section; however, its anterior extremity is oval. The chromatin is electron-dense and compact, although there are clear areas in the posterior peripheral regions. In the nucleus-flagellum transition region, the cross-section of the centriole adjunct is oval, with a pleated border and an E-PTA-positive peripheral region. The axoneme shows a 9 + 9 + 2 microtubule arrangement. The microtubules are E-PTA positive and, at the posterior extremity, the accessories are the last to terminate. The diameters and shapes of the two mitochondrial derivatives are almost identical. One begins beside the nuclear base and the other after the centriole adjunct. Posteriorly, they terminate together, immediately before the axoneme. Both have mitochondrial cristae and a region of paracrystalline material; however, the format and arrangement of this material differs from those of all other species previously studied. The paracrystalline material is more strongly E-PTA positive than the cristae region. Accessories bodies are electron-dense and located between the mitochondrial derivatives and the axoneme. In general, P. nasuta spermatozoa are similar to those of the majority of Hymenoptera; however, they have various exclusive characteristics that may be useful for studying the phylogeny and taxonomy of the superfamily Chrysidoidea and of Hymenoptera in general.     

Ultrastructure of the spermatozoa of Psammotettix striatus (Linnaeus) and Exitianus nanus (Distant) (Hemiptera: Auchenorrhyncha: Cicadellidae: Deltocephalinae)

Previous studies of insect spermatozoa indicate that these specialized cells have undergone significant morphological evolution and exhibit traits useful for reconstructing phylogenetic relationships. Although leafhoppers (Cicadellidae) are among the largest and most economically important insect families, few comparative studies of their spermatozoa have been published. Here, the ultrastructure of mature spermatozoa of two leafhoppers Psammotettix striatus (Linnaeus) and Exitianus nanus (Distant), representing two different tribes of the largest leafhopper subfamily, Deltocephalinae, was examined by light and transmission electron microscopy. The shape and ultrastructure of spermatozoa of the two species are very similar to those of other Cicadellidae as well as other Auchenorrhyncha, comprising a conical acrosome invaginated to form a subacrosomal space, a filiform homogeneously condensed nucleus, a lamellate centriolar adjunct connecting the nucleus with the mid-piece/flagellum, a long flagellum with a 9 + 9 + 2 axoneme pattern and two symmetrical mitochondrial derivatives with an orderly array of peripheral cristae, and two drop-shaped accessory bodies. They may be distinguished by the size of the sperm, and the shape of the nucleus, accessory bodies, and paracrystalline region of mitochondrial derivatives. The fine morphology and ultrastructure of spermatozoon in P. striatus and E. nanus are illustrated, along with a brief discussion of the implications for classification and phylogenetic analyses of the subfamily.     

Sperm structure of Mecoptera and Siphonaptera (Insecta) and the phylogenetic position of<Emphasis Type="Italic"> Boreus hyemalis</Emphasis>

Sperm ultrastructure has been studied in three species of the taxa Mecoptera and Siphonaptera. The spermatozoon of the scorpion fly Panorpa germanica shows an apical bilayered acrosome, a helicoidal nucleus, a centriolar region and a 9+2 flagellar axoneme helicoidally arranged around a long mitochondrial derivative. A second mitochondrial derivative is very short and present only in the centriolar region. A single accessory body is present and it is clearly formed as a prolongation of the centriole adjunct material. Two lateral lamellae run parallel to the nucleus. The snow fly Boreus hyemalis has a conventional sperm structure and shows a bilayered acrosome, a long nucleus, a centriolar region, two mitochondrial derivatives and two accessory bodies. The axoneme is of the 9+2 type and is flattened at the tail tip. Both P. germanica and B. hyemalis have two longitudinal extra-axonemal rods and have a glycocalyx consisting of longitudinal parallel ridges or filaments. The spermatozoon of the flea Ctenocephalides canis has a long apical bilayered acrosome, a nucleus, a centriolar region, a 9+2 axoneme wound around two unequally sized mitochondrial derivatives, and two triangular accessory bodies. In the posterior tail end the flagellar axoneme disorganises and a few microtubular doublets run helicoidally around the remnant mitochondrial derivative. The glycocalyx consists of fine transverse striations. In all three species, the posterior tail tip is characterised by a dense matrix embedding the disorganised axoneme. From this comparative analysis of the sperm structure it is concluded that Mecoptera, as traditionally defined, is monophyletic and that B. hyemalis is a member of Mecoptera rather than of Siphonaptera.     

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.     

Ultrastructure des spermatozoides des males haploides et diploides de Diadromus pulchellus wesmeal (Hymenoptera : Ichneumonidae)

The mature spermatozoa were described in the haploïd and diploïd males of Diadromus pulchellus Wesmeal (Hymenoptera : Ichneumonidae). Diploïd males produce spermatozoa, which do not seem to be different from those produced by haploïd males. The spermatozoon is about 100 μm long, and consists of a head, 0.8 μm in diameter, and a tail 0.3 μm in diameter. Its anterior part shows an acrosomal complex, including a perforatorium and a compact and electron-dense fusiform nucleus. The postnuclear region includes a longitudinal axoneme with 2 mitochondrial derivatives. The axoneme shows 2 typical central units, 9 peripheral doublet microtubules, 9 accessory internal tubules, and 9 external microtubules with dense contents. In the testes of diploïd males, a great number of abnormal spermatozoa were observed. These spermatozoa with degenerative structures are probably not implicated in egg fertilization.     

Fine structure of the spermatozoa of Crassostrea gigas (Mollusca,Bivalvia)

We describe sperm ultrastructure and acrosome differentiation during spermiogenesis in Crassostrea gigas (Mollusca Bivalvia). The sperm cell is a uniflagellated cell of the primitive type. The head region contains a rounded or conical nucleus surmounted by small acrosome. This organelle consists of a membrane-bound acrosomal granule, the contents of which have a homogeneous density, except in the anterior region, which is positive for PTA. The acrosome also surrounds the perforatorium, which includes oriented fibrillar elements: this is the axial body. The middle piece contains four mitochondria encircling two perpendicular centrioles. The distal centriole is provided with a system of mechanical fixation to the plasma membrane, consisting of nine fibers in radial arrangement. The tail flagellum, about 50 m?m long, contains the usual microtubular axoneme. © 1993 Wiley-Liss, Inc.     

Flagellate spermatozoa of Protura (Insecta,Apterygota) are motile

A new model of sperm axoneme with 16 + 0 doublets is described. The spermatozoon of Acerentulus confinis (Apterygota : Protura) has a short conical acrosome, a long helicoidal nucleus, well-developed centriolar adjunct material, and a long flagellum. Using fixation with a glutaraldehyde-tannic acid mixture, without osmium post-fixation, doublet protofilaments, inner dynein arms, radial spokes, nexin bridges, and Y-links of the sperm axoneme of A. confinis and Acerentomon italicum were clearly observed. Optical observation shows that the proturan flagellate spermatozoa are motile cells. The process involving the transformation of the spermatozoa from a coiled to an elongated swimming form was studied by scanning electron microscope. The findings confirmed that flagellar motility is due to the presence of a single dynein arm on doublets in spite of the unusual axonemal pattern.     

Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera,Apidae)

Fiorillo, B. S., Zama, U., Lino‐Neto, J. and Báo, S. N. 2010. Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera, Apidae). —Acta Zoologica (Stockholm) 91 : 176–183. In Xylocopa frontalis the reproductive tract is composed of testes, deferent ducts, seminal vesicles, accessory glands and an ejaculatory duct. Each testis comprises four testicular tubules in which multiple cysts are present containing approximately 64 spermatozoa per cyst. The seminal vesicle consists of an epithelium, a thick basement lamina and a muscular external sheet. In the luminal region some vesicles can be observed; however, the epithelial cells of the seminal vesicle do not display morphological features associated with secretory functions. The spermatozoa, measuring approximately 260 µm long, are similar to the hymenopteran pattern. The head region consists of an acrosome with an inner perforatorium that penetrates an asymmetrical nuclear tip. The nucleus is linear, electron‐dense and its posterior tip projects into the beginning of the axoneme. The centriolar adjunct is asymmetric with many electron‐lucent lacunae interspersed throughout. The axoneme has the 9 + 9 + 2 pattern of microtubules and in the posterior region the central microtubules finish first, followed by the doublets and finally the accessory microtubules. The mitochondrial derivatives are asymmetric in both length and diameter with paracrystalline material present only in the larger one. These features may be useful characters for taxonomy and phylogenetic studies.     

The sperm of Hexagenia (Pseudeatonica) albivitta Walker (Ephemeroptera: Fossoriae: Ephemeridae)

This study describes the sperm morphology of the mayfly Hexagenia (Pseudeatonica) albivitta (Ephemeroptera). Its spermatozoon measures approximately 30 μm of which 9 μm corresponds to the head. The head is composed of an approximately round acrosomal vesicle and a cylindrical nucleus. The nucleus has two concavities, one in the anterior tip, where the acrosomal vesicle is inserted and a deeper one at its base, where the flagellum components are inserted. The flagellum is composed of an axoneme, a mitochondrion and a dense rod adjacent to the mitochondrion. A centriolar adjunct is also observed surrounding the axoneme in the initial portion of the flagellum and extends along the flagellum for at least 2 μm, surrounding the axoneme in a half‐moon shape. The axoneme is the longest component of the flagellum, and it follows the 9+9+0 pattern, with no central pair of microtubules. At the posterior region of the flagellum, the mitochondrion has a dumb‐bell shape in cross sections that, together with the rectangular mitochondrial‐associated rod, is responsible for the flattened shape of the flagellum. An internal membrane is observed surrounding both mitochondrion and its associated structure.     

The double sperm line in Isochaetides (Annelida,Clitellata, Tubificidae)

Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenarius, a species belonging to the subfamily Tubificinae inhabiting the sediments of Lake Baikal. As all tubificines, Isochaetides produces two types of spermatozoa, named eusperm and parasperm. The eusperm are the fertilizing male gametes and consist, in sequence, of an acrosome, a nucleus, a mitochondrial mid-piece, and a tail. The parasperm have the same general architecture, but differ in cytological details: the acrosome is shorter, devoid of a perforatorium, and the acrosome vesicle has a different, simpler, shape. The nucleus is much shorter and rectilinear (the eusperm nucleus is twisted). The mid-piece mitochondria are less numerous but their overall volume is larger. The flagellum has a plasma membrane largely separated from the axoneme, and is devoid of glycogen granules. After mating, the two sperm types gather in the spermathecae to form spermatozeugmata; in these structures the parasperm form an external sheath involving the centrally located eusperm and their tails are connected by conspicuous septate junctions. Parasperm nuclei are produced through a process of fragmentation of the 'spermatocytes', whereas the flagellar basal bodies are produced by a process similar to that giving rise to basal bodies in ciliated epithelia.