1,720,997 research outputs found
FIGS 12–15 in Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785)
No full textFIGS 12–15. Trophi of Anomopus telphusae, SEM pictures. (12) Cephalic. (13) Caudal view. Trophi of Embata parasitica, SEM pictures. (14) Cephalic. (15) Caudal view. Scale bar: 5 µm.Published as part of Fontaneto, D., Segers, H. & Melone, G., 2004, Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785), pp. 1225-1232 in Journal of Natural History 38 (10) on page 1230, DOI: 10.1080/0022293031000155197, http://zenodo.org/record/465850
FIGS 7–9 in Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785)
No full textFIGS 7–9. Trophi of Lecane branchicola, SEM pictures. (7) Rami and unci, ventral view. (8) Fulcrum and rami, dorsal view. (9) Manubrium. Scale bar: 2 µm.Published as part of Fontaneto, D., Segers, H. & Melone, G., 2004, Epizoic rotifers (Rotifera: Monogononta, Bdelloidea) from the gill chambers of Potamon fluviatile (Herbst, 1785), pp. 1225-1232 in Journal of Natural History 38 (10) on page 1228, DOI: 10.1080/0022293031000155197, http://zenodo.org/record/465850
The ultrastructure of Xenopus spermatozoon.
No full textThe spermatozoon of Xenopus consists of a coiled head 20 μm long and of a tail 40 μm long. The acrosome is a thin vesicle capping the anterior region of the nucleus. A manchette of mitochondria surrounds the posterior region of the nucleus, the two centrioles, and the beginning of the flagellum. The flagellum shows a conventional 9∗2+2 appearance and is devoid of any accessory structure
Structure and function of the metachronal wave in Tubifex tubifex spermatozeugmata (Annelida, Oligocheta)
No full textThe spermatozeugmata of Tubifex tubifex are bundles of spermatozoa, stored in the spermathecae and composed of two types of sperm cells. The eupyrene, fertilizing, spermatozoa are stored parallel to the central axial cylinder, whereas the oligopyrene spermatozoa are helically arranged in the cortex. The main portions of their tails are connected by a junctional complex. When placed in Ringer solution the free extremities of the oligopyrene sperm tails start beating with metachronal waves, forming a series of wave fronts that are helically arranged around the spermatozeugma. The wavelength is 2.76 μm and the beat frequently is around 10 Hz. Besides the functions already suggested for the spermatozeugmata (holding together fertilizing spermatozoa; selecting nutrients from the lumen of the spermatheca) another function is proposed: the oligopyrene sperm tails, which form the helical metachronal wave, may help the transport of the spermatozeugma from the spermatheca to the opening of the spermathecal duct
Exploring motion using geometric morphometrics in microscopic aquatic invertebrates: ‘modes’ and movement patterns during feeding in a bdelloid rotifer model species
Full text linkBackground: Movement is a defining aspect of animals, but it is rarely studied using quantitative methods in microscopic invertebrates. Bdelloid rotifers are a cosmopolitan class of aquatic invertebrates of great scientific interest because of their ability to survive in very harsh environment and also because they represent a rare example of an ancient lineage that only includes asexually reproducing species. In this class, Adineta ricciae has become a model species as it is unusually easy to culture. Yet, relatively little is known of its ethology and almost nothing on how it behaves during feeding. Methods: To explore feeding behaviour in A. ricciae, as well as to provide an example of application of computational ethology in a microscopic invertebrate, we apply Procrustes motion analysis in combination with ordination and clustering methods to a laboratory bred sample of individuals recorded during feeding. Results: We demonstrate that movement during feeding can be accurately described in a simple two-dimensional shape space with three main ‘modes’ of motion. Foot telescoping, with the body kept straight, is the most frequent ‘mode’, but it is accompanied by periodic rotations of the foot together with bending while the foot is mostly retracted. Conclusions: Procrustes motion analysis is a relatively simple but effective tool for describing motion during feeding in A. ricciae. The application of this method generates quantitative data that could be analysed in relation to genetic and ecological differences in a variety of experimental settings. The study provides an example that is easy to replicate in other invertebrates, including other microscopic animals whose behavioural ecology is often poorly known
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
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