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ULTRASTRUCTURE OF THE SPERMATOZOON OF ELENCHUS-JAPONICUS AND ITS BEARING ON THE PHYLOGENY OF STREPSIPTERA
No full textThe fine structure of the mature spermatozoon of the strepsipteran Elenchus japonicus Esaki and Hashimoto (Elenchidae) is described using transmission electron microscopy. The spermatozoon was seen to have an elongated head. a tail containing a 9+9+2 axoneme, two mitochondrial derivatives and two accessory sheaths. The monolayered acrosome is conical in shape while the nucleus exhibits an internal channel of uncondensed chromatin. The tail is long, and in its final portion, the axoneme, loses its elements progressively. These results are compared with the sperm ultrastructurc of Xenos moutoni De Buysson (Stylopidae) and with those of other insect orders, particularly the Coleoptera
FINE-STRUCTURE OF THE SPERMATOZOON OF THE STREPSIPTERAN XENOS-MOUTONI
No full textSpermatozoa of Xenos moutoni De Buysson belonging to the order Strepsiptera (Insecta) were examined by electron microscopy. The spermatozoon was seen to have an elongated head and a tail containing a 9 + 9 + 2 axoneme and two mitochondrial derivatives of equal size. The pear-shaped acrosome is characterised by a mono-layered structure and terminates anteriorly forming two pyramidal evaginations. The nucleus exhibits an external portion of dense chromatin and an internal one of uncondensed material. The latter occupies a central position at the base and becomes progressively peripheral at the apex. The tail is long and in its final portion the axoneme loses its elements progressively. These results have been compared with the ultrastructure of the spermatozoa of Coleoptera which have been considered as a sister group of Strepsiptera
COMPARATIVE SPERMATOLOGY OF 4 SPECIES OF STREPSIPTERA AND COMPARISON WITH A SPECIES OF PRIMITIVE COLEOPTERA (RHIPIPHORIDAE)
No full textThe comparative spermatology of 4 strepsipteran species, namely, Xenos moutoni De Buysson, Elenchus tenuicornis (Kirby), Elenchus japonicus Esaki and Hashimoto and Halictophagus chilensis Hofmann, have been studied by transmission electron microscopy. The spermatozoon of all 4 species examined were seen to have: an elongated head characterized by a nucleus with an internal channel of uncondensed chromatin, a one-layered acrosome, and a tail containing a 9 + 9 + 2 axoneme and 2 partially crystallized mitochondrial derivatives. Each sperm, nevertheless, shows a few peculiarities that confirm the taxonomic value of comparative spermatology. In addition, the strepsipteran spermatozoa were seen to have a different organization to that of Pelecotoma fennica Pewkull (Rhipiphoridae, Pelecotominae), which has the typical structure of a coleopteran sperm. It was characterized by a 3-layered acrosomal complex, a tail with a 9 + 9 + 2 axoneme flanked by 2 accessory bodies and 2 mitochondrial derivatives. From the spermatological point of view, primitive Coleoptera cannot be considered to be closely related to Strepsiptera
THE SPERMATOZOON OF HALICTOPHAGUS-CHILENSIS HOFMANN (STREPSIPTERA, HALICTOPHAGIDAE)
No full textThe fine structure of mature spermatozoon of the strepsipteran Halictophagus chilensis Hofmann was studied by light and transmission electron microscopy. The spermatozoon was seen to have an elongated head and a tail with a > axoneme and two mitochondrial derivatives. The mono-layered acrosome is conical in shape and the long nucleus has an internal channel of uncondensed chromatin. The tail is five times longer than the head and the end of the axoneme shows progressive loss of microtubules. These findings are compared with the sperm ultrastructure of other strepsipteran species studied so far
Testis morphology and spermatogenesis in two species of Elenchus (Strepsiptera : Elenchidae)
No full textTestes ultrastructure and spermatogenesis were studied in two species of Strepsiptera (Insecta), namely, Elenchus tenuicornis and E. japonicus, using light and electron microscopy. In both species, the testis is paired and consists of several large irregularly shaped follicles. Each follicle consists of a single clone of germ cells surrounded by a thin epithelium. During the larval and pupal stages, all the germ cells of each testis develop synchronously, and at eclosion, the gonads contain solely mature sperm. One of the most interesting findings is the morphogenesis of a large nuclear vesicle bounded by the fenestrate parr of the nuclear envelope. This vesicle contains an electron-dense spherical structure, the chromatoid body. At the end of spermiogenesis, both the nuclear vesicle and its chromatoid body are eliminated with the excess cytoplasm. Large drops of residual cytoplasm containing several nuclear vesicles are present in the lumen of the testis and inside the cytoplasm of phagocytic cells. (C) 1998 Elsevier Science Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Fine structure of the Nassonow's gland in the neotenic endoparasitic of female Xenos vesparum (Rossi) (Strepsitera, Insecta)
No full textNassonow's gland consists of a number of cells with ducts that open on to the ventral surface of the brood canal in the cephalothoracic region of a neotenic female strepsipteran. The structural organization of the gland is reminiscent of the class 3 of the epidermal gland cells as defined by Noirot and Quennedey [Ann. Rev. Entomol. 19 (1974) 61], which consists of secretory and duct forming cells. The ultrastructure of the Nassonow's gland is described in female Xenos vesparum (Rossi) parasitic in the social wasp Polistes dominulus Christ. The large secretory cells are clustered in groups of three to four, rich in smooth endoplasmic reticulum and produce a secretion made up of lipids. In young females, just before mating, the ultrastructure of the cells and their inclusions indicate that they are active. In old-mated females the Nassonow's gland degenerates. Microvilli line an extracellular cavity and there are pores present in the irregularly thick cuticle of the efferent duct. The small duct forming cells, intermingle with epidermal cells, overlap secretory cells and produce a long efferent duct, the cuticle of which becomes thick close to its opening in the brood canal. Nassonow's gland could be the source of a sex pheromone, which might be capable of attracting the free-living male to a permanently endoparasitic female. © 2004 Elsevier Ltd. All rights reserved
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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