1,721,093 research outputs found
Influence of temperature on the larval development of the edible crab Cancer pagurus
No full textThe influence of temperature on larval survival and development was studied in the edible crab, Cancer pagurus, from a population off the Island of Helgoland, North Sea. In rearing experiments conducted at six different temperatures (6°, 10°, 14°, 15°, 18°, 24° C), zoeal development was only completed at 14° and 15° C. Instar duration of the Zoea I was negatively correlated with temperature. A model relating larval body mass to temperature and developmental time suggests that successful larval development is possible within a narrow temperature range (14° ± 3° C) only. This temperature optimum coincides with the highest citrate synthase (CS) activity found at 14° C. A comparison for intraspecific variability among freshly hatched zoeae from different females (CW 13 - 17cm, N = 8) revealed that both body mass and elemental composition varied significantly. Initial larval dry weight ranged from 12.1 to 17.9 µg/individual, the carbon content from 4.6 to 5.8 µg/individual, nitrogen from 1.1 to 1.3 µg/individual, and the C:N ratio from 4.1 to 4.4. A narrow larval temperature tolerance range of C. pagurus as well as the indication of intraspecific variability in female energy allocation into eggs may indicate a potential vulnerability of this species to climate change. Large-scale studies on the ecological and physiological resilience potential of this commercially fished predator are needed
Early egg traits in Cancer setosus (Decapoda, Brachyura): effects of temperature and female size
No full textPrevious study on Cancer setosus (Molina, 1782) had shown that latitudinal changes in temperature control the number of annual egg masses. This study focused on the effects of pre-oviposition temperature and female size on egg-traits in C. setosus from Northern (Antofagasta 23ºS) and Central-Southern (Puerto Montt 41ºS) Chile. Blastula eggs produced in nature ranged in dry mass (DM) from 9.1 to 15.1 µg, in carbon (C) from 4.8 to 8.4 µg, in nitrogen (N) from 1.0 to 1.6 µg, in C:N ratio between 4.7 and 5.4, and in volume (V) between 152 and 276 mm3 x 10-4 per female. Blastula eggs from females caught early in the reproductive season in Puerto Montt (09/2006) were significantly higher in DM, C, N, and V than those of females caught two months later (11/2006), reflecting a seasonal increase in water temperature. In Puerto Montt “early” and “late” season blastula eggs were about 32% and 20% higher in DM, C, N, and V as eggs from Antofagasta, respectively. Subsequent egg masses produced in captivity in Puerto Montt followed this pattern of smaller eggs with lower DM, C, and N content at higher pre-oviposition temperatures. In Antofagasta no significant difference in DM, C, N and V between eggs produced in nature and subsequent eggs produced in captivity was found and all egg traits were significantly positively affected by maternal size. Reproductive plasticity in C. setosus helps explaining the species wide latitudinal distribution range
Saving by freezing? Oxygen consumption rates of Adamussium colbecki in a latitudinal context
No full textStandard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O 2 g -1 h -1) and "winter" (106.52±39.65 µl O 2 g -1 h -1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage
Growth efficiency and temperature in scallops: A comparative analysis of species adapted to different temperatures
No full text1. Data were collected on metabolic activity and growth in pectinid bivalves from published studies. The resulting database comprised three types of data sets: (i) synoptic data (13 populations, 7 species), where both individual growth performance and metabolism are known, (ii) 'metabolism only' data (82 populations, 13 species), and (iii) 'growth only' data (198 populations, 26 species).
2. In pectinid bivalves belonging to different species and living under different environmental conditions metabolic activity (standard metabolic rate, SMRAvg, Q10 = 2·97) is more closely related to temperature than individual growth (overall growth performance, OGP index P, Q10 = 1·12).
3. The synthesis of the two corresponding Arrhenius equations shows that the relationship between the SMRAvg-to-OGP ratio and temperature follows the Arrhenius model, too, with Q10 = 2·26.
4. SMRAvg-to-OGP is an inverse proxy for growth efficiency, hence growth efficiency decreases with rising temperature across a wide range of pectinid populations and species. Thus, there is strong empirical evidence that elevated temperature constrains growth efficiency in scallops and that adaptation does not fully compensate for this effect
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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