1,721,421 research outputs found
The relationship between nutritional stress and digestive enzyme activities in sea cucumber Holothuria scabra
No full textThe sea cucumber Holothuria scabra (sandfish) was studied to determine what digestive enzymes are present, to perform a basic characterization of their activity, and to attempt to correlate enzyme activity with nutritional status of the animal. Enzymes alpha amylase, protease (as well as chymotrypsin), cellulase, mannanase, agarase, and xylanase were detected. The enzymes trypsin, alginate lyase and laminarinase were also tested for, but the presence of trypsin was inconclusive, and no alginate lyase or laminarinase was detected. The pH optimum of protease was pH 5 and that of alpha amylase pH 7. Alpha amylase, protease, chymotrypsin, cellulase and mannanase continued to digest their substrates over time. A 2-week starvation experiment showed changes in alpha amylase and protease levels. No differences in cellulase, mannanase, agarose or xylanase activity were detected as a result of the starvation experiment. Another starvation experiment wherein sandfish intestines were sampled every 3 days for 15 days showed that only alpha amylase levels changed with starvation. All samples had lower alpha amylase activity after the withdrawal of feed compared to the day 0 samples. These results suggest the possibility of the use of alpha amylase activity as an indicator of nutritional status, particularly feed deprivation, in sandfish
Utilization of organic waste from black tiger shrimp, Penaeus monodon, by sandfish, Holothuria scabra
No full textIn Southeast Asian countries, a large proportion of shrimp aquaculture has switched its target species from native black tiger shrimp, Penaeus monodon, to exotic P. vannamei because of frequent viral disease outbreaks. One of the causes of disease outbreaks is thought to be poor water and sediment conditions in the shrimp pond, which aggravate disease symptoms. To establish co-culture methods of black tiger shrimp and sandfish, Holothuria scabra, for possible mitigation of shrimp pond eutrophication and prevention of disease outbreaks, laboratory experiments were conducted at the Aquaculture Department, Southeast Asian Fisheries Development Center (SEAFDEC/AQD) in Iloilo, Philippines. A feeding trial of juvenile H. scabra using benthic diatom, Navicula ramossisima, and powdered P. monodon feed showed that H. scabra do not grow with fresh shrimp feed on a hard substrate. A feeding trial with and without sand substrate with shrimp feed as food showed that the substrates enhance the growth of H. scabra. H. scabra juveniles were found to grow with detritus and P. monodon feces as food sources in tanks. It was also shown that addition of ground oyster shell to the sand substrate enhances the growth of H. scabra when fed with N. ramossisima. Thus, these results suggest that H. scabra can grow by feeding on organic matter present in a P. monodon pond and may be used to mitigate organic load in P. monodon ponds
Co-culture trials of sandfish Holothuria scabra and black tiger shrimp Penaeus monodon in mangroves
No full textTo address its mandate to develop environment-friendly culture techniques, the Southeast Asian Fisheries Development Center, Aquaculture Department (SEAFDEC/AQD) is trying to establish a culture system in mangroves for commercially important aquaculture species. Recently, SEAFDEC/AQD has successfully produced sandfish, Holothuria scabra, in the hatchery. Using hatchery-bred juveniles, monoculture and co-culture trials are being conducted in ponds, pens and cages. This study investigated the feasibility of the co-culture of black tiger shrimp, Penaeus monodon, and H. scabra in the mangroves by comparing growth and survival in monoculture and co-culture conditions. Water and sediment quality were compared between treatments. Results showed that growth and survival of P. monodon (P. monodon only = 48.8±4.9%; P. monodon + H. scabra = 46.1±7.4%) and H. scabra (H. scabra only = 13.1±6.1%; P. monodon + H. scabra = 12.3±6.2%) grown together or separately did not significantly differ. P. monodon survivial was positively correlated while growth negatiely correlated with temperature. Feed input significantly increased sulfide levels in both treatments (P. monodon; P. monodon + H. scabra) and sulfide significantly differed between treatments with the highest concentration in P. monodon only, then P. monodon + H. scabra and H. scabra only. Ammonia concentrations followed the same trend as sulfide but did not significantly differ among treatments. P. monodon cultured in mangroves were not affected by the white spot syndrome virus which affected neighboring culture ponds. Results of these initial trials may not be conclusive yet but show a promising culture system for P. monodon that may be integrated with the mangroves.This study was funded by SEAFDEC Aquaculture Department and the Japan International Research Center for Agricultural Sciences under Study Code FS-11-Y2010D
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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