1,720,972 research outputs found
Discrimination of toad calls by smooth newts: support for the heterospecific attraction hypothesis
No full textThe 'heterospecific attraction hypothesis' (HAH) has been proposed to describe interactions between migrant and resident birds where migrants may indirectly select habitats using the presence/absence of residents. This hypothesis might be extended to other taxa, such as amphibians, which migrate yearly to breeding sites, sharing them with other species. However, the ability of amphibians to be cue-users is not quite obvious as for birds, and must be assessed first. Therefore, in this study we investigated how smooth newts, Lissotriton vulgaris, oriented facing two known species (the common toad, Bufo bufo, and the green toad, Pseudoepidalea viridis) and whether they oriented preferentially towards the calls of species that indicate the more suitable pond for breeding (B. bufo). Newts showed positive phonotactic responses for both species but clearly oriented towards B. bufo when the playbacks of the two toads were presented simultaneously. Our results support the idea that the 'HAH' might be extended to other taxa than birds
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
Effects of female mating status on copulation behaviour and sperm expenditure in the freshwater crayfish Austropotamobius italicus
No full textSperm competition models predict that males should adjust their sperm expenditure according to the risk and/or intensity of sperm competition. In this paper, we analysed copulatory behaviour of both sexes and sperm expenditure in relation to female mating status (virgin or mated) in the freshwater crayfish Austropotamobius italicus, a species where males have been reported to feed on and remove sperm laid by other males. The same females were allowed to be inseminated sequentially by two males, and we compared the sexual behaviours of partners between the first (virgin females) and the second mating (mated females). We found that female resistance did not differ between the first and the second mating, nor males refused or took more time to mount a mated female. However, when mating with a mated female, males reached an effective copulation position significantly later. This occurred because second-mating males removed, by eating, all or most spermatophores previously deposited by first males. As removal was often incomplete, this resulted in a
larger amount of sperm being deposited on female ventral
parts after the second mating, although second males did
not allocate more sperm to mated females than first males
did. Thus, the peculiar mode of sperm competition, where
males remove previously deposited sperm, and the onsequent
predictable strong last male prevalence in paternity.
likely led to the observed lack of adjustment of sperm
expenditure to female mating status in this specie
Leukocyte differential counts and morphology from twelve European lizards
Full text linkThe present study reports the morphology of leukocytes of 12 European lacertid lizards (Podarcis sicula, P. tiliguerta,
P. melisellensis, P. bocagei, P. muralis, Algyroides nigropunctatus, Lacerta viridis, L. bilineata, L. trilineata, L. oxycephala, Timon
lepidus, and Zootoca vivipara) stained using May–Grünwald/Giemsa method. The morphology of white blood cells was very
similar among species, suggesting a relative morphological uniformity within the lacertid lizards. For six species (i.e. P. sicula,
P. tiliguerta, P. melisellensis, P. bocagei, P. muralis, and A. nigropuncatus), we determine the leukocyte differential counts, which
may be considered representative of the normal values of the corresponding populations. These results may be useful either
in clinical investigation to detect pathologies in wild individuals, as in management and conservation projects to assess the
general health conditions of natural wild lizard populations
Repeated matings and sperm depletion in the freshwater crayfish Austropotamobius italicus
No full text1. In sexually reproducing organisms, the energetic costs of spermatogenesis can be considerable, and can limit the reproductive potential of the males. In species where males mate more than once during the reproductive season, the costs of sperm production are generally predicted to result in a decrease of ejaculate size and quality with successive fertilizations.
2. In this study we examined the variation in ejaculate size among successive fertilizations in a long-lived freshwater crayfish species, Austropotamobius italicus.
3. Sexually active adult males of various sizes were allowed to mate repeatedly with different females on consecutive days. Trials for a given male ended when he copulated but did not release any sperm or refused to mate.
4. Males fertilized between 0 and 4 females, and most (42.5%) fertilized a single female. The overall number of females fertilized by a given male decreased with increasing male body size. Ejaculate size decreased markedly with consecutive fertilizations in a similar fashion among both large and small males, while simultaneously increasing with female body size. The total ejaculate size over successive fertilizations decreased with increasing male size.
5. Our study indicates that either sperm production or release involves non-trivial costs in freshwater crayfish, and suggests that large/old males may face greater difficulties in gamete release than small/young ones, as shown by the lower number of females fertilized by large compared with small males, which may reflect the ongoing senescence of their reproductive performance
Blood cell morphology of the Moorish gecko, Tarentola mauritanica
No full textThe morphology of erythrocytes, trombocytes, monocytes, basophils and lymphocytes on Moorish geckos (Tarentola mauritanica) is quite similar to that of other reptiles, even though some peculiarities were detected for heterophils and eosinophils. Moreover, we found a fourth type of granulocyte whose morphology highly differs from both heterophils and eosinophils. Sexually-based differences in the relative abundance of different types of leukocytes was detected: lymphocytes were the most frequent in females, while heterophils and eosinophils prevailed in males. Interestingly, in most individuals we found intra-erythrocytic vacuoles whose structure is similar to that previously described as Chelonoplasma in tortoises and Serpentoplasma in snakes
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
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