1,721,016 research outputs found
A peculiar new virus-spermatozoon association in the bug Raphigaster nebulosa (Poda) (Heteroptera-Insecta)
No full textThe sperm of the heteropteran bug Raphigaster nebulosa (Poda) are of two types, differing in length and size of their flagella. The thicker sperm are shorter than the thinner ones and have large mitochondrial derivatives. The presence of virus particles associated with the plasma membrane of thinner sperm is described for the first time; thicker sperm are immune to virus infection. The fact that virus particles are present on thinner sperm only initiates considerations on the transmission of virus
The ultrastructure of the spermatheca of Mordellistena brevicauda (Coleoptera, Tenebrionoidea) and the associated bacterial cells
Full text linkThe ultrastructural study on the female reproductive system of the beetle M. brevicauda (Mordellidae) confirmed the positive correlation between the length of the sperm and the size of the female seminal receptacle (Spermatheca). The spermatheca of the species is characterized by an apical bulb-like structure where the spermathecal duct forms numerous folds filled with sperm. At this level many bacterial cells are present intermingled with the duct folds. Some are organized in large structures, such as bacteriomes, while other are single bacteriocytes. The latter are often found near the basal lamina of duct epithelium. In addition, some bacteria are visible in the cytoplasm of the duct epithelial cells. Interestingly, bacterial cells have never been observed in the duct lumen. The possible function of the bacterial cells is discussed
The spermatogenesis and sperm structure of Timema poppensis (Insecta: Phasmatodea)
No full textThe ultrastructure of spermatogenesis and spermatozoa was studied in Timema poppensis Vickery & Sandoval, 1999, a putative basal taxon of Phasmatodea. The apical portion of testis follicles consists of spermatogonial cells with polymorphic nuclei. Primary spermatocytes display very short primary cilia originating from the peripheral centrosomes. Early spermatids develop a conspicuous "nebenkern" consisting of fused mitochondria. They have a single peripheral centriole with microtubular triplets, which expresses a 3. 6-μm-long cilium featuring a 9 + 2 axonemal pattern. In a later stage, the centriole and the ciliary shaft displace toward the inner part of the cytoplasm by an infolding of the plasma membrane. Mature spermatids exhibit a derived centriole with microtubule doublets devoid of dynein arms, which is equipped with a dense arc-like outer structure. Ciliary degeneration was not observed during spermiogenesis. Spermatozoa are short flagellate cells about 55-60 μm in length. They are characterized by a three-layered acrosomal complex. The distinctive bell-shaped morphology of the acrosome vesicle is likely an autapomorphic trait of Timema. The flagellum has a 9 + 9 + 2 axoneme, two accessory bodies, two flattened cisterns, and two elongated mitochondrial derivatives. Results support the hypothesis that Phasmatodea, comprising Timema + Euphasmatodea, form a monophyletic group. The presence of 17 protofilaments in the wall of accessory microtubules and the flattened configuration of the flagellum are potential apomorphic groundplan features of the order. Within Phasmatodea, a key evolutionary divergence was from the conventional insect spermiogenesis and sperm structure of Timema, to the unusual spermiogenetic process and peculiar sperm structure of Euphasmatodea. As a result, Timema retains more sperm character states found in the polyneopteran ground pattern, while Euphasmatodea have evolved outstanding sperm autapomorphies, like the loss of mitochondria and flattened cisterns, and the presence of strongly expanded accessory bodies. © 2012 Springer-Verlag
Structural organization of the "zipper line" in Drosophila species with giant spermatozoa
No full textThe "zipper line" of Drosophila melanogaster and of Drosophila species characterized by giant spermatozoa (D. hydei, D. kanekoi and D. bifurca) was studied by electron microscopy using conventional thin-sections, lectin labeling and freeze-fracture replicas. In cross sections the membrane specializations are located either at the level of the short cistern close to the large mitochondrial derivative where a small tuft of glycocalyx is visible or, in species characterized by long spermatozoa, along a cistern beneath the plasma membrane. In correspondence of such cistern, the plasma membrane exhibits a thick and extended glycocalyx. At this level, as well as at the short tuft of D. melanogaster, α-mannose residues were detected. The "zipper" of D. melanogaster consists of rows of intramembrane particles longitudinally disposed along the sperm tail and associated with the external face of the plasma membrane. On the protoplasmatic face a narrow ribbon of transversal grooves is visible. Freeze-fracture replicas have revealed, in the region characterized by extended glycocalyx, the presence of a large ribbon of intramembrane particles disposed in parallel transversal rows, associated with the protoplasmatic membrane face. On the complementary external face a ribbon of parallel transversal grooves was observed. It is suggested that membrane specializations are mechanical devices to protect spermatozoa from torsion and bending in the seminal vesicles and then in the female storage organ. © 2007
A novel membrane specialization in the sperm tail of bug insects (heteroptera)
No full textThe sperm tail of bug insects has 9 + 9 + 2 flagellar axonemes and two mitochondrial derivatives showing two to three crystalline inclusions in their matrix. During spermiogenesis, the axoneme is surrounded by a membrane cistern which, at sperm maturity, reduces to two short cisterns on the opposite sides of the axoneme adhering to the mitochondrial derivatives. Filamentous bridges connect the intertubular material of the axoneme to these cisterns. Such bridges, which represent a peculiar feature of bug insects, are resistant to detergent treatment, whereas part of the intertubular material and the inner content of microtubular doublets are affected by the treatment. After freeze-fracture replicas, at the insertion of the bridges to the cisternal membrane, the P-face of this membrane shows a characteristic ribbon consisting of four rows of 11 ± 1 nm staggered intramembrane particles, 13 ± 2 nm apart along each row. The bridges could be able to maintain the axoneme in the proper position during flagellar beating avoiding distortion affecting sperm motility. © 2009 Wiley-Liss, Inc
The sperm ultrastructure and spermiogenesis of Tribolium castaneum (Coleoptera: Tenebrionidae) with evidence of cyst degeneration
No full textPrevious studies on the spermatogenesis of tenebrionid beetles showed the unusual formation of two antiparallel sperm bundles per cyst. In this work we reported this feature also in Tribolium castaneum using light and transmission electron microscopy. The sperm structure of T. castaneum, similar to other tenebrionids, consists of a three-layered acrosome, an elongated nucleus and a flagellum with a 9. +. 9. +. 2 axoneme, two accessory bodies and two asymmetric mitochondrial derivatives. The presence of two antiparallel sperm bundles per cyst also in Meloidae and Rhipiphoridae suggests that it is a strong trait synapomorphic for Tenebrionoidea. The huge degeneration of whole sperm cells in several cysts of testes during spermiogenesis is also described
The ultrastructure of sperm and female sperm storage organs in the water strider Gerris lacustris L. (Heteroptera) and a possible example of genital coevolution
No full textThe fine structural organization of the male and the female inner reproductive apparatuses of the water-strider Gerris lacustris was studied. The sperm of the species shows a long helicoidal acrosome provided with longitudinal tubules, and a short nucleus. The flagellum is characterized by crescent mitochondrial derivatives and a 9 + 9 + 2 axoneme, as occurs in all Heteroptera. The female reproductive apparatus is characterized by an extremely long spermathecal duct, filled with sperm, which plays the role of the main sperm storage organ. The duct has a thin epithelium surrounded by a complex of secretory and duct-forming cells. The spermathecal duct flows into the gynatrial sac. This region, together with the fertilization chamber, exhibits a simple epithelium with deep apical plasma membrane invaginations, and it does not show conspicuous secretions. The basal cell region shows plasma membrane infoldings forming thin cytoplasmic bands hosting mitochondria and large intercellular spaces. This organization is typical of epithelia active in fluid reabsorption. Two lateral large gynatrial glands open into the gynatrial sac. Such glands also exhibit secretory and duct forming cells. The same structure of these glands is also present along the proximal region of the fecundation canal. The duct forming cells of these regions have very wide ducts with peculiar cuticular finger-like structures at their opening into the gland duct lumen. The results of the present study suggest the occurrence of a coevolution between the sperm and the spermathecal duct lengths
The sperm structure of Clinidium canaliculatum (Costa): A contribution to the systematic position of Rhysodidae (Coleoptera: Carabidae)
Full text linkThe systematic position and the phylogenetic relationship of Rhysodidae members is still debated, with some authors considering the group as a separate family of Adephaga, while for others they could be a subfamily of Carabidae. The group have morphological traits quite different from Carabidae and an aberrant behaviour compared to ground beetles being not predaceous. The sperm ultrastructure of C. canaliculatum was studied comparatively with other species of beetles, Carabidae in particular. The results indicate that the sperm structure of this species is similar to that of the Carabinae species. As in these species, C. canaliculatum has sperm conjugates with an apical conical cap protecting the heads and the initial region of flagella. This sperm appearance is also shared by another species of Rhysodidae, Omoglymmius hamatus. The material of the apical cap consists of an electron -dense material with a peculiar outer net configuration. Many species of Carabidae, however, can present a different type of sperm conjugation, the spermatostyle: a long rod -like structure where the individual sperms have only the most apical part inserted in the cortical area and the flagella are completely free. C. canaliculatum sperm are endowed with a mono -layered acrosome, a nucleus of variable shape along its length, a flagellum consisting of a typical axoneme 9 thorn 9 thorn 2, provided with 16 protofilaments in the tubular wall of accessory tubules, two asymmetric mitochondrial derivatives with the left one larger than the opposite one, and the right accessory body elongated and larger than the opposite one. These sperm characteristics, which are shared also by another member of the group, suggest the demotion of the family Rhysodidae to the subfamily Rhysodinae within Carabidae, a result also supported by recent molecular data. (c) 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
The spermatheca ultrastructure of the ground beetle Clinidium canaliculatum (Costa) (Carabidae, Rhysodinae)
No full textThe ground beetle Clinidium canaliculatum is a member of Rhysodinae, a taxon with still discussed systematic position. The spermatheca of this species is a small cylindrical structure connected to the common oviduct by a thin duct. The ultrastructure of the organ has revealed that the apical receptacle is provided with an epithelium lined by a thick cuticle from the deeper region of which several finger-like cuticular structures extend into the cytoplasm. On these structures adhere microtubule bundles that cross the whole cytoplasm to anchor on short densities along the basal plasma membrane. These specializations are strongly reminiscent of the hemidesmosomes, possibly playing a mechanical role enabling the cells to resist to the muscle contractions pushing the sperm towards the spermathecal duct. The cells are rich in mitochondria and glycogen granules and they are possibly involved in fluid uptake from the spermathecal lumen. The spermathecal duct has a simple epithelium lined by a soft cuticle. The sperm present in the apical receptacle and in the duct lumen maintain the structure described in the male genital apparatuses. They are generally free and embedded in a homogeneous electron- dense material. Occasionally, a sperm bundle, still with an apical cap, was visible in the spermathecal receptacle
The Sperm Ultrastructure of the Nitidulidae Meligethes flavimanus (Stephens, 1830) and of the Phalacridae Olibrus affinis (Sturm. 1807) (Coleoptera Cucujoidea)
Full text linkThe sperm ultrastructure of two members of Cucujoidea was described. The Nitidulidae Meligethes flavimanus sperm are long cells extending along the cyst cell with a series of helicoidal tracts. Each sperm cell has a bi-layered acrosome, a cylindrical nucleus and two mitochondrial derivatives of unequal sizes, the one on the right side larger than the opposite one. The axoneme has the common 9+9+2 microtubule pattern and is flanked by two accessory bodies. The one on the right side has an extension of electron-dense material (a puff-like body) reaching the smaller mitochondrial derivative. The cytoplasm of the sperm cyst hosts numerous bacteria. The sperm of the Phalacridae Olibrus affinis are very long cells that form numerous foldings throughout the cyst. The sperm cell has a long bi-layered acrosome, a cylindrical nucleus and a conventional 9+9+2 axoneme. As in the previous species, two mitochondrial derivatives of different sizes are present, the one on the right side larger than the second one, only 1/3 of the other. Two accessory bodies are on both sides of the axoneme. That on the right side is very large, triangular shaped, while on the opposite side a small electron-dense dot is present. The study performed on the two species of Cucujoidea confirms a close phylogenetic relationship between this superfamily and those of Chrysomeloidea and Curculionoidea, a finding also supported by molecular data
- …
