1,720,966 research outputs found
Variability of GnRH secretion in two goby species with socially controlled alternative male mating tactics
No full textMale reproductive phenotypic plasticity related to environmental–social conditions is common among teleost fish. In several species, males
adopt different mating tactics depending on their size, monopolizing mates when larger, while parasitizing dominant male spawns when smaller.
Males performing alternative mating tactics are often characterized by a strong dimorphism in both primary and secondary reproductive traits.
According to studies on sex-changing species and on species where only one male morph is reproductively active, male alternative phenotypes are
expected to vary also in gonadotropin-releasing hormone (GnRH) neurons in forebrain preoptic area (POA). Here, we compared the intra- and
inter-sexual variations in number and size of GnRH neurons, along with gonads and male accessory structure investment, in two goby species, the
grass goby, Zosterisessor ophiocephalus, and the black goby, Gobius niger, characterized by male alternative mating phenotypes. In both species,
older and larger males defend nests, court and perform parental care, while younger and smaller ones try to sneak territorial male spawning. We
found that grass goby and black goby have different patterns of GnRH expression. Grass goby presents a clear intra-sexual dimorphism in GnRH
expression, related to the occurrence of alternative mating tactics, while in the black goby, only inter-sexual differences are observed. The interand
intra-specific variability in the GnRH neurons in these two goby species is discussed in light of the differences in migratory behavior, nest
type, and mating system
Changes along the male reproductive axis in response to social context in a gonochoristic gobiid, Zosterisessor ophiocephalus (Teleostei, Gobiidae), with alternative mating tactics
No full textSexual selection has given rise, in several taxa, to intrasexual variation in male phenotype. While evolutionary studies have provided
explanations of the adaptive function of this dramatic male phenotypic diversity, the proximate control of its expression has still to be
completely understood. Several observations, primarily from sex-changing species, indicated a major role of social interactions in
reproductive axis regulation and consequently in the expression of alternative male phenotypes. Here we documented changes along the male
reproductive axis in response to social context in a gonochoristic species, the grass goby Zosterisessor ophiocephalus, where fully functional
alternative male mating tactics appear to be expressed as an ontogenetic gradient. In the grass goby, larger and older males dig a nest and
perform parental care, while smaller males sneak fertilization during territorial male spawning. Territorial males are characterized by a higher
number of gonadotropin-releasing hormone (GnRH) neurons in forebrain preoptic area, smaller testes, larger seminal vesicles, and viscous
ejaculates that last longer and contain fewer sperm than those of sneakers. To experimentally investigate the role of social factors in inducing
changes along the male reproductive axis, sneakers were tested in two different situations: nesting alone or with ripe females. Sneakers that
mated and performed parental care showed dramatic changes in brain, reproductive apparatus morphology, and ejaculate traits. GnRHimmunoreactive
cells in forebrain preoptic area increased in number, reaching values typical of wild-caught parental males. Testes size
decreased while seminal vesicle size increased and ejaculates showed lower sperm densities. These results were discussed within the
framework of the social transduction hypothesis, which predicts that social experience should mediate, through a cascade of internal
processes, shifts between morphs throughout life
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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