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Distal Centriole (distal + centriole)
Selected AbstractsFine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopyACTA ZOOLOGICA, Issue 1 2010Sonja Fürböck Abstract Fürböck, S., Patzner, R.A. and Lahnsteiner, F. 2008. Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy. , Acta Zoologica (Stockholm) 91: 88,95 The fine structure of spermatozoa of sneep or nase, Chondrostoma nasus, and lake chub, Rutilus meidingerii, was investigated by means of scanning and transmission electron microscopy. The uniflagellate spermatozoa of C. nasus lacked an acrosome. The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) and lacked lateral fins. The uniflagellate spermatozoa of R. meidingerii were made up of a head, also without an acrosome. For both species the sperm tail was covered by a plasma membrane. The midpiece of C. nasus contained five or six mitochondria on average, vesicles and glycogen granules, whereas the midpiece of R. meidingerii had seven mitochondria of a spherical or ovoid shape. The centriolar complex was located caudolaterally with respect to the nucleus. In C. nasus, the centrioles were orientated at an angle of 125° to each other, whereas the centrioles of R. meidingerii were at an angle of 110°. The fine structure of C. nasus and R. meidingerii spermatozoa showed species-specific differences in the position of the proximal centriole relative to the distal centriole, the position and number of mitochondria, size of the head and the length of the flagellum. (Correction added on 11 June 2009, after first online publication: The word ,axoneme' was deleted from the sentence ,The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) axoneme and lacked lateral fins.') [source] Ultrastructure of spermatozoa of lizards in the genus Mabuya from Central BrazilACTA ZOOLOGICA, Issue 1 2009S. M. De Sá Mandel Abstract This is the first description of spermatozoal ultrastructure of Mabuya skinks. The spermatozoa of the species studied are filiform, consisting of a head region, a midpiece and a tail. The head is characterized by the following features: a depressed acrosome anteriorly, an acrosome vesicle divided into cortex and medulla, paracrystalline subacrosomal material, a pointed tip perforatorium, a circular perforatorium base plate inside the subacrosomal cone, an epinuclear lucent zone separated from the subacrosomal cone by a membrane, a large nuclear rostrum, and round nuclear shoulders. The midpiece presents a bilateral stratified laminar structure, a distal centriole, peripheral fibres 3 and 8 grossly enlarged, columnar mitochondria with linear cristae, dense body rings and a triangular annulus. Finally, the tail is composed of a principal piece and an end piece. An axoneme and a fibrous sheath characterize the principal piece, and the end piece is formed only by an axoneme, which loses its pattern in the last portion. Comparisons with members of Teiidae revealed differences in the numbers of dense rings. A well-developed epinuclear lucent zone in Mabuya is less prominent among teiids. In the spermatozoa of Mabuya, the first ring of dense bodies is very large, uniquely resembling the condition present in snakes. [source] Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implicationsACTA ZOOLOGICA, Issue 4 2005Barrie G. M. Jamieson Abstract The spermatozoon of Apus apus is typical of non-passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non-passerines. All non-passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non-passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA,DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae. [source] Sperm morphology in the black coral Cirrhipathes sp. (Anthozoa, Antipatharia)INVERTEBRATE BIOLOGY, Issue 3 2008Elda Gaino Abstract. Male polyps of the antipatharian Cirrhipathes sp., collected along the coral reef of Siladen Island (Sulawesi, Indonesia), were studied in order to gain an insight into the reproductive biology. Spermatocysts (maximum size 120 ,m) are located within the primary gametogenic mesenteries and are separated by mesenteric cell cytoplasmic extensions. Sperm, maturing along radial rows, have a fairly round shape and contain a series of electron-dense vesicles in the apical nuclear region. A single mitochondrion flanks the nucleus. A peculiar cup-like electron-dense body, edged with regularly spaced electron-dense granules, is interposed between the nucleus and the tail, and delimits a central region that includes two centrioles. Cross-sections of the cup-like body reveal that the distal centriole has a pericentriolar system, consisting of nine arms arranged in a radial pattern. Each arm branches into three processes that are connected to the electron-dense granules. Indirect evidence of spawning is derived from the accumulation of sperm in the gastric cavity. This process takes place through the lysis of the cells bordering the mesenteries. Intact cells of this bordering layer appear to be involved in the phagocytosis of non-expelled gametes. [source] Sperm ultrastructure and spermiogenesis in two Exogone species (Polychaeta, Syllidae, Exogoninae)INVERTEBRATE BIOLOGY, Issue 4 2002Adriana Giangrande The spermatozoa of Exogone naidina and E. dispar are characterized by a prominent bell-shaped acrosome, a spheroidal nucleus, and a conventional flagellum. During spermiogenesis, the acrosomal vesicle undergoes conspicuous modifications leading to its final bell shape with a posterior opening. The subacrosomal material initially shows radiating filaments but in mature sperms it appears as a meshwork of electron-opaque material. The acrosomal axis is oblique with respect to the main longitudinal sperm axis. The chromatin is arranged in electron-opaque strands in the early spermatids, then becomes amorphous, and is finally organized in filaments in mature sperms. Centrioles are orthogonally arranged beneath the nucleus and fibers radiate from the distal centriole to contact the plasma membrane and the single mitochondrion. The latter is located eccentrically on the side of the nucleus opposite the acrosome. A disk-shaped structure is evident beneath the distal centriole. The flagellar axoneme has a 9+2 microtubule pattern. A conspicuous glycocalyx surrounds the flagellar plasma membrane, and an electron-lucent space is present between these two structures at the distal tip of the flagellum. We compare the sperm morphology of these two species of Exogone with that described in other members of the subfamily Exogoninae. The fine structure of these two species supports the occurrence of an ent-aquasperm type within Exogoninae, in accordance with the brood strategy present within this subfamily. The mode of reproduction is of taxonomic importance for defining subfamilies within Syllidae, and is likely also of phylogenetic significance. Because epitoky is probably plesiomorphic, the ent-aquasperm type found in Exogoninae can be considered a derived feature within Syllidae. [source] Reproductive morphology of Brittanichthys axelrodi (Teleostei: Characidae), a miniature inseminating fish from South AmericaJOURNAL OF MORPHOLOGY, Issue 1 2007Robert Javonillo Abstract Light and electron microscopy were used to investigate the morphology of reproductive characters in a characid fish, Brittanichthys axelrodi. Spermatozoa were found in ovaries of females, thereby confirming insemination in this species. Bony hooks can be found on the fourth unbranched ray and branched rays 1,4 of the anal fin and the unique sigmoidally-curved ray of the caudal fin in mature males. Testes have three distinct regions: an anterior spermatogenic region, an aspermatogenic middle region lined with a simple squamous epithelium and used for storage of mature spermatozoa, and a posterior region of coiled chambers lined with a high simple cuboidal epithelium. The most posterior region appears to be instrumental in the formation and storage of spermatozeugmata, unencapsulated sperm packets. Thus far, this tripartite testis morphology is unique among characids. The mature spermatozoon has an elongate nucleus (,5 ,m in length). A striated rootlet originates at the anterior end of the distal centriole and continues to the anterior tip of the cell. The striated rootlet wraps around the entire ventral area of the anterior part of the nucleus and appears to continue around the anterior tip of the nucleus and down the dorsal side as electron-dense material. Several large, spherical mitochondria (,0.6 ,m in diameter) with lamellar cristae overlap the posterior end of the nucleus and continue beyond together with the cytoplasmic collar that contains the flagellum which lacks axonemal fins. Each spermatozeugma is lanceolate in shape when sectioned mid-sagitally, with the core staining positively for mucopolysaccharides. In both sexes, the gonopore opens posterior to the anus, with the urinary pore having a separate opening posterior to the gonopore. Bands of skeletal muscle were found in the area of the male gonopore. These morphological features are likely linked to the reproductive mode of insemination, a trait that is so far as known, relatively rare among teleost fishes, but is proving increasingly frequent among certain groups of characid fishes. J. Morphol, 2006. © 2006 Wiley-Liss, Inc. [source] Ultrastructure of the spermatid of Caprimulgus europaeus Linnaeus 1758, the European nightjar (Aves; Caprimulgidae), with phylogenetic implicationsJOURNAL OF MORPHOLOGY, Issue 10 2006Sandro Tripepi Abstract The sperm of Caprimulgus europaeus is typical of other nonpasserines in many respects. Features shared with Paleognathae and Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a perforatorium and endonuclear canal; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around a central axis (here maximally six mitochondria in ,10 tiers); and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. A major (apomorphic) difference from paleognaths and galloanserans is the short distal centriole, the midpiece being penetrated for most of its length by the axoneme and for only a very short proximal portion by the centriole. Nonpasserines differ from paleognaths in that the latter have a transversely ribbed fibrous sheath, whereas in nonpasserines it is amorphous, as in Caprimulgus, or absent. The absence of an annulus is an apomorphic feature of Caprimulgus, apodiform, psittaciform, gruiform, and passerine sperm, homoplastic in at least some of these. In contrast to passerines, in Caprimulgus the cytoplasmic microtubules in the spermatid are restricted to a transient longitudinal manchette. The structure of the spermatid and spermatozoon is consistent with placement of the Caprimulgidae near the Psittacidae, but is less supportive of close proximity to the Apodidae, from DNA,DNA hybridization and some other analyses. J. Morphol. © 2006 Wiley-Liss, Inc. [source] | ||||||||||