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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of spermiogenesis inVampyroteuthis infernalis Chun — a relict cephalopod mollusc (1990)
    Springer
    Helgoland marine research 44 (1990), S. 95-107 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spermiogenesis in the relict deep-sea cephalopodVampyroteuthis infernalis Chun is examined using transmission electron microscopy (TEM), and the results compared with available data on other cephalopods. Early spermatids ofVampyroteuthis exhibit an ovoid nucleus (with dense irregular patches), numerous mitochondria and a pair of triplet substructure centrioles (arranged parallel to each other). Subsequently, the following morphological changes take place: (1) nuclear contents condense into a fibrous reticulum, then into thick fibres; (2) the acrosomal vesicle (presumably Golgi-derived) positions itself in a shallow depression at the nuclear apex; (3) the flagellum forms from one of the two centrioles; (4) mitochondria cluster around the flagellum at the base of the nucleus; (5) a dense, fibrous plug forms within the basal invagination of the nucleus. Microtubules surround the acrosome and condensing nucleus of spermatids. The dense plug is of special systematic importance since it also occurs in spermatids and spermatozoa ofOctopus spp., but not in any investigated species of the Sepiida, Sepiolida or Teuthida. Late spermatids and mature spermatozoa ofVampyroteuthis strongly resemble developing spermatids ofOctopus, suggesting a close phylogenetic relationship betweenVampyroteuthis (and the Vampyromorpha) and octopods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02365433
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructure of paraspermatozoa of cerithiacean gastropods (prosobranchia: Mesogastropoda) (1986)
    Springer
    Helgoland marine research 40 (1986), S. 177-199 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using transmission electron microscopy, paraspermatozoa of representative species of the families Cerithiidae, Potamididae, Planaxidae, Dialidae and the genusAustralaba (family position uncertain) have been examined and compared with those produced by other prosobranchs, particularly other investigated cerithiaceans. Special attention is focused on the phylogenetic importance of paraspermatozoa and euspermatozoa within the superfamily Cerithiacea. The paraspermatozoa of cerithiacean gastropods fall into two structural categories: (1) those with a ‘head’ region and a ‘tail tuft’ (number of tails and the length of the tail tuft variable — Cerithiidae, Planaxidae, Potamididae, Modulidae, Turritellidae, Campanilidae, Pleuroceridae,Obtortio, Australaba); and (2) those with an elongate, vermiform body filled with large electron-dense vesicles and up to ninety axonemes — the latter emerging as numerous short tails from the posterior half of the paraspermatozoon body (Dialidae).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987294
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  • 3
    Electronic Resource
    Electronic Resource
    The ultrastructure of spermatozoa and spermiogenesis in pyramidellid gastropods, and its systematic importance (1988)
    Springer
    Helgoland marine research 42 (1988), S. 303-318 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ultrastructural observations on spermiogenesis and spermatozoa of selected pyramidellid gastropods (species ofTurbonilla, Pyrgulina, Cingulina andHinemoa) are presented. During spermatid developement, the condensing nucleus becomes initially anterio-posteriorly compressed or sometimes cup-shaped. Concurrently, the acrosomal complex attaches to an electrondense layer at the presumptive anterior pole of the nucleus, while at the opposite (posterior) pole of the nucleus a shallow invagination is formed to accommodate the centriolar derivative. Midpiece formation begins soon after these events have taken place, and involves the following processes: (1) the wrapping of individual mitochondria around the axoneme/coarse fibre complex; (2) later internal metamorphosis resulting in replacement of cristae by paracrystalline layers which envelope the matrix material; and (3) formation of a glycogen-filled helix within the mitochondrial derivative (via a secondary wrapping of mitochondria). Advanced stages of nuclear condensation (elongation, transformation of fibres into lamellae, subsequent compaction) and midpiece formation proceed within a microtubular sheath (‘manchette’). Pyramidellid spermatozoa consist of an acrosomal complex (round to ovoid apical vesicle; column-shaped acrosomal pedestal), helically-keeled nucleus (short, 7–10 μm long, shallow basal invagination for axoneme/coarse fibre attachment), elongate helical midpiece (composed of axoneme, coarse fibres, paracrystalline and matrix materials, glycogen-filled helix), glycogen piece (length variable, preceeded by a dense ring structure at junction with midpiece). The features of developing and mature spermatozoa observed in the Pyramidellidae are as observed in opisthobranch and pulmonate gastropods indicating that the Pyramidelloidea should be placed within the Euthyneura/Heterobranchia, most appropriately as a member group of the Opisthobranchia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02366047
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure of spermiogenesis of Philippia (Psilaxis) oxytropis, with special reference to the taxonomic position of the architectonicidae (Gastropoda) (1982)
    Springer
    Zoomorphology 101 (1982), S. 197-214 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312434
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of paraspermatozoa, euspermatozoa and eusperm-like spermatozoa ofObtortio cf.fulva (Prosobranchia: Cerithiacea) (1982)
    Springer
    Helgoland marine research 35 (1982), S. 489-500 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cerithiaceanObtortio cf.fulva produces three distinct types of spermatozoa: (1) paraspermatozoa, (2) euspermatozoa and (3) eusperm-like spermatozoa. Like most mesogastropods, euspermatozoa ofObtortio are composed of a conical acrosome, short posteriorly invaginated nucleus, elongate midpiece and glycogen piece, and short terminal region. The midpiece, however, is distinctly cerithiacean in structure and is composed of four non-helical midpiece elements. Eusperm-like spermatozoa closely resemble euspermatozoa, but have a very short nucleus only one half to one third the length of the euspermatozoon nucleus. Paraspermatozoa of this species are composed of (1) “head” (mosaic sheath of dense blocks enveloping multiple axonemes which attach anteriorly to a long apical structure), (2) “midpiece” (multiple axonemes interspersed with elongate mitochondria), and (3) multiple tail tuft (axonemes each ensheathed by glycogen granules). The possible role of eusperm-like spermatozoa is briefly discussed together with the taxonomic implications of the structure of the three sperm types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01999137
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  • 6
    Electronic Resource
    Electronic Resource
    Euspermatozoa and paraspermatozoa of the relict cerithiacean gastropod,Campanile symbolicum (prosobranchia, mesogastropoda) (1986)
    Springer
    Helgoland marine research 40 (1986), S. 201-218 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Euspermatozoa and paraspermatozoa ofCampanile symbolicum Iredale, 1917 — a large, relict cerithiacean from Western Australia — have been examined using transmission electron microscopy and phase-contrast light microscopy. The euspermatozoa resemble those of many other mesogastropods with the important exception that the midpiece region exhibits unusual and possibly unique features. These include possession of seven or eight straight, periaxonemal elements (each containing scattered cristae) and a closely associated sheath composed of electrondense segments which are semicylindrical in shape and longitudinally aligned. This sheath — here termed the ‘accessory midpiece sheath’-surrounds only one half of the periaxonemal midpiece elements and lies outside the mitochondrial membrane (but nevertheless within the plasma membrane). Two types of paraspermatozoa occur inCampanile: (1) those with a nuclear core within the mosaic sheath of the head (nucleate paraspermatozoa) and (2) those lacking a nuclear core (dense blocks of mosaic sheath surrounding one to three axonemes — anucleate paraspermatozoa). An acrosome-like structure forms the apex of the head in both types of paraspermatozoa, while beyond the head region, electron-dense glycogen deposits are associated with each of the multiple tails. While the form ofCampanile paraspermatozoa suggests links with families such as the Cerithiidae, Potamididae and Turritellidae, the highly unusual morphology of the euspermatozoan midpiece indicates that the Campanilidae should occupy an isolated position within the superfamily Cerithiacea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987295
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of spermatozoa and spermiogenesis inSpirula spirula (L.): systematic importance and comparison with other cephalopods (1990)
    Springer
    Helgoland marine research 44 (1990), S. 109-123 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spermatozoa and spermiogenesis in the deep-water cephalopodSpirula sprirula (L.) are examined using transmission electron microscopy. Mature spermatozoa (taken from spermatophores) are elongate cells 115–120 μm long, composed of a conical acrosomal vesicle, cylindrical nucleus (6.8–7 μm long), flagellum and a loose mitochondrial sleeve — the latter concealing the proximal 6–8 μm of the flagellum. The acrosomal vesicle is 2.8 μm long with fibro-granular contents and an electron-lucent apical zone. Subacrosomal material, organized as closely packed granules, fills a basal invagination of the acrosomal vesicle. In early spermatids the flagellum is derived from a triplet substructure centriole positioned close to the developing nuclear invagination. As flagellum formation proceeds, the acrosomal vesicle (produced evidently through Golgi secretion) attaches to the condensing nucleus. Spermatids are connected by cytoplasmic bridges throughout their development, and exhibit a perinuclear sheath of microtubules from the onset of the fibrous stage of nuclear condensation (mid-, late spermatids). In mid-spermatids, mitochondria collect posterior to the nucleus and subsequently are packed into a cylindrical extension of the plasma membrane to form the periflagellar mitochondrial sleeve. These features of spermiogenesis and mature spermatozoa ofSpirula clearly associate the Spirulidae with the Sepiida, Teuthida and Sepiolida — particularly with the latter order. However, pending results of a thorough review of coleoid sperm morphology, the Spirulidae are here included in their own order — Spirulida (of Reitner & Engeser, 1982) — rather than in either the Sepiida or Sepiolida.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02365434
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructure of Euspermatozoa of cerithiacean gastropods (Prosobranchia: Mesogastropoda) (1983)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 178 (1983), S. 57-75 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Euspermatozoa of selected cerithiacean gastropods have been studied using transmission electron microscopy and the results compared (primarily) with previous studies of mesogastropod and neogastropod euspermatozoa. Cerithiacean euspermatozoa each possess a well-defined acrosome (extremely varied in shape), a short (2.25 - 3 μm), very electron-dense nucleus, an elongate midpiece, and an elongate glycogen piece. A dense ring structure associated with the plasma membrane occurs at the junction of the midpiece and glycogen piece. While features such as the dense ring structure and the systematic periaxonemal arrangement of “glycogen” granules can be understood from a purely functional standpoint, it is suggested that euspermatozoon features also provide information of taxonomic and phylogenetic relevance. On the basis of euspermatozoon midpiece structure, true cerithiaceans can be easily distinguished from other mesogastropods and from neogastropods and are divided tentatively into two groups: Group 1 (Turritellidae, Cerithiidae, Australaba (family uncertain), Planaxidae, Potamididae (subfamily Batillariinae)), and Group 2 (Potamididae (subfamily Potamidinae), Modulidae, Obtortio (family uncertain)). Using midpiece and acrosomal features, group 1 can be further subdivided into two subgroups: Subgroup 1(i) (Turritellidae, Cerithiidae, Australaba) and Subgroup 1(ii) (Planaxidae, Potamididae (subfamily Batillariinae)). It is suggested that the pronounced differences existing between the two subfamilies of the Potamididae may indicate the necessity for a separate family for the Batillariinae.
    Additional Material: 103 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051780105
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructure of spermiogenesis in the gastropod Calliotropis glyptus Watson (Prosobranchia: Trochidae)with special reference to the embedded acrosome (1989)
    New York, NY : Wiley-Blackwell
    Gamete Research 24 (1989), S. 9-19 
    Details
    ISSN: 0148-7280
    Keywords: Mollusca ; centrioles ; spermatid nucleus ; Trochoidea ; systemtics ; Archaeogastropoda ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Testicular spermatozoa and sperm development in the archaeogastropod Calliotropis glyptus Watson (Trochoidae: Trochidae) are examined using transmission electron microscopy and formalin-fixed tissues. During spermiogenesis, the acrosome, formed evidently through fusion of Golgi-derived proacrosomal vesicles, becomes deeply embedded in the condensing spermatid nucleus. Two centrioles (proximal and distal), both showing triplet microtubular substructure, are present in spermatids - the distal centriole giving rise to the sperm tail and its associated rootlet. During formation of the basal invagination in the spermatid nucleus, centrioles, and rootlet move towards the nucleus and come to lie totally within the basal invagination. Mitochondria are initially positioned near the base of the nucleus but subsequently become laterally displaced. Morphology of the mature spermatozoon is modified from that of the classic primitive or ect-aquasperm type by having 1) the acrosome embedded in the nucleus (the only known example within the Mollusca), 2) a deep basai invagination in the nucleus containing proximal and distal centrioles and an enveloping matrix (derived from the rootlet), 3) laterally displaced periaxonemal mitochondria, and 4) a tail extending from the basal invagination of the nucleus. Implantation of the acrosomal complex and centrioles within imaginations of the nucleus and lateral displacement of mitochondria effectively minimize the length of the sperm head and midpiece. Such modifications may be associated with motility demands, but this remains to be established. The unusual features of C. glyptus spermatozoa, though easily derivable from ‘typical’ trochoid sperm architecture, may prove useful in delineating the genus Calliotropis or tracing its relationship to other genera within the trochid subfamily Margaritinae.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120240104
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  • 10
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    A family-level Tree of Life for bivalves based on a Sanger-sequencing approach (2017)
    Elsevier
    Details
    Publication Date: 2017-02-01
    Print ISSN: 1055-7903
    Electronic ISSN: 1095-9513
    Topics: Biology
    Published by Elsevier
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