1,720,968 research outputs found
Rainbow trout (Oncorhynchus mykiss, Walbaum ) develop a more robust body shape under organic rearing
No full textProlonged exposure to captive conditions has led to the development of a rainbow trout 'farmed' phenotype, which is different from that of wild trout. Selection for desirable productive traits in hatcheries has resulted in the development of some morphological traits that are maladaptive in nature. The recent development of organic aquaculture, guided by the well-being of the fish, could potentially produce a new farmed phenotype that would be more adaptive in nature. In this study, rainbow trout reared in intensive and organic farms were compared by means of shape analysis, to detect patterns of shape variation associated with rearing environment. The results of this study highlight a significant effect of the rearing method on rainbow trout shape: organically reared trout showed a higher body profile, in particular in the head and trunk regions, shorter median fins and a deeper caudal peduncle. A combined effect of density and habitat complexity could have contributed to the observed shape differences: in organic rearing systems, lower densities and steady water could increase territoriality and aggressive interactions, promoting body designs more functional in rapid attacks and escapes
Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) develop a more robust body shape under organic rearing
Full text linkProlonged exposure to captive conditions has led to the development of a rainbow trout ‘farmed’ pheno- type, which is different from that of wild trout. Selec- tion for desirable productive traits in hatcheries has resulted in the development of some morphological traits that are maladaptive in nature. The recent development of organic aquaculture, guided by the well-being of the fish, could potentially produce a new farmed phenotype that would be more adaptive in nature. In this study, rainbow trout reared in intensive and organic farms were compared by means of shape analysis, to detect patterns of shape variation associated with rearing environment. The results of this study highlight a significant effect of the rearing method on rainbow trout shape: organi- cally reared trout showed a higher body profile, in particular in the head and trunk regions, shorter median fins and a deeper caudal peduncle. A combined effect of density and habitat complexity could have contributed to the observed shape differences: in organic rearing systems, lower densi- ties and steady water could increase territoriality and aggressive interactions, promoting body designs more functional in rapid attacks and escapes
Composition and trophic structure of motile fauna populations in macrophytes of a natural CO2 vent system
No full textAs a consequence of global change, ocean acidification is predicted to increase progressively in the next centuries and evidence suggests that decreased levels of pH could lead to severe modifications in marine communities. Levante Bay in Vulcano Island (Aeolian Archipelago, Italy) hosts a shallow submarine volcanic CO2 vent, representing a natural laboratory suitable to study the effects of ocean acidification on marine ecosystems. However, in addition to direct CO2 effects, volcanic emissions may also increase a number of trace elements, providing harsh features to the surrounding environment. The aim of this work was to examine the motile fauna populations associated to macrophytes, Cymodocea nodosa and macroalgal beds, in order to detect any change in composition and trophic structure attributable to the peculiar features of the volcanic vent. We compared the structure of populations sampled in a site close to the vents (weakly acidified) and in a control site (normal pH conditions). Samples were collected in May 2013 using an airlift sampler on 30 cm quadrats. Results revealed clear differences in macrophyte composition, cover and biomass between the two sites, as well as in the structure of the faunal community, with the weakly acidified site showing higher abundances of polychaetes and amphipods and a marked reduction in molluscs in comparison with the control site. Furthermore, stable isotope analysis showed that in the weakly acidified site δ13C and δ15N signatures of primary producers were depleted, while the isotopic niche space of the motile fauna became narrower and markedly shifted towards lower values. These findings highlight the importance of studying the effects of ocean acidification on the composition and structure of food webs within benthic communities and its ecological implications are discussed in terms of diversity and local adaptation
Segnalazione della presenza di una facies a maerl (Corallinales) lungo le coste dell'Isola di Ischia.
No full textLOX-Induced Lipid Peroxidation Mechanism Responsible for the Detrimental Effect of Marine Diatomson Zooplankton Grazers
No full textResistance of seagrass habitats to ocean acidification via altered interactions in a tri-trophic chain
Full text linkDespite the wide knowledge about prevalent effects of ocean acidification on single species, the consequences on species interactions that may promote or prevent habitat shifts are still poorly understood. Using natural CO2 vents, we investigated changes in a key tri-trophic chain embedded within all its natural complexity in seagrass systems. We found that seagrass habitats remain stable at vents despite the changes in their tri-trophic components. Under high pCO2, the feeding of a key herbivore (sea urchin) on a less palatable seagrass and its associated epiphytes decreased, whereas the feeding on higher-palatable green algae increased. We also observed a doubled density of a predatory wrasse under acidified conditions. Bottom-up CO2 effects interact with top-down control by predators to maintain the abundance of sea urchin populations under ambient and acidified conditions. The weakened urchin herbivory on a seagrass that was subjected to an intense fish herbivory at vents compensates the overall herbivory pressure on the habitat-forming seagrass. Overall plasticity of the studied system components may contribute to prevent habitat loss and to stabilize the system under acidified conditions. Thus, preserving the network of species interactions in seagrass ecosystems may help to minimize the impacts of ocean acidification in near-future oceans.The research was funded by an ASSEMBLE access project within the EU FP7/2007–2013 program (grant agreement n° 227799) hosted by MCG at the SZN. The Portuguese FCT– Fundação para a Ciência e a Tecnologia funded BMC in the ambit of the contract program DL57/2016/CP1361/CT0004 and CCMAR through the project UID/Multi/04326/2019.info:eu-repo/semantics/publishedVersio
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
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