The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Ryan D Dorland - One of the best experts on this subject based on the ideXlab platform.
-
aggregation and vertical migration behavior of Euphausia superba
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Meng Zhou, Ryan D DorlandAbstract:Aggregation and vertical migration behavior of Euphausia superba were studied in Marguerite Bay and its vicinity west of the Antarctic Peninsula using a vessel-mounted, Acoustic Doppler Current Profiler, and a Multiple Opening and Closing Nets and Environmental Sensing System, during the 2001 and 2002 fall US Southern Ocean GLOBEC project cruises. The kinematics of aggregation behavior of E. superba associated with diel migration is studied using observations of their abundance and swimming velocities: during the day, E. superba reduce their swimming at a depth of 250 m; and at night, they swim randomly at their cruising speed in the upper part of an aggregation near the surface, and coherently as schooling in the lower part of an aggregation. The causes for the aggregation behavior and vertical migration of krill are explored by examining the relationship with ice coverage and presence of predators. The motion of euphausiids is further analyzed in terms of kinetic energy and force balance, leading to new considerations of mathematical theories and models of aggregation behavior. The results show a diel variation of the energy demand for maintaining their locomotion. The horizontal scale of an aggregation is studied in conjunction with horizontal gradients of currents. Results indicate that the swimming capability of euphausiids determines the maintenance of an aggregation in the mesoscale circulation field.
Maria Terbojevich - One of the best experts on this subject based on the ideXlab platform.
-
Chitosans from Euphausia superba. 2: Characterization of solid state structure
Carbohydrate Polymers, 1992Co-Authors: B. Focher, Annamaria Naggi, Giangiacomo Torri, Alessandro Cosani, Maria TerbojevichAbstract:Abstract Chitosans from Euphausia superba of different degrees of acetylation (42%, 28% and The X-ray powder patterns indicated a decrease of order with decreasing the degree of acetylation as well as after regeneration and acid treatments. Similarly, the CP-MAS 13C-NMR and FTIR spectra exhibited a general broadening of signals suggesting the occurrence of new conformations for chitosans after regeneration. Furthermore, samples treated with hydrochloric acid showed some structural modifications which accounted for their behaviour in solution as reported in the first part of this study.
-
Chitosans from Euphausia superba. 1: Solution properties
Carbohydrate Polymers, 1992Co-Authors: Maria Terbojevich, B. Focher, Annamaria Naggi, Alessandro Cosani, Giangiacomo TorriAbstract:Abstract A technological development of chitosan (copolymer of N -acetylglucosamine and glucosamine) is based on the knowledge of parameters such as composition. types of sequence, chain length and distribution. In addition to the sample source, these factors are related to preparation and purification methods. In this connection the authors examined chitosan samples having the same origin ( Euphausia superba ), but different degrees of acetylation, as well as materials which were subjected to regeneration and beating processes. In addition, the authors prepared chitosan samples of different degrees of polymerization by hydrolysis of commercial chitosan of high degree of acetylation under different pH and temperature conditions. The samples were characterized in 0·1 n CH 3 COOH (HAc) - 0·2 m NaCl by intrinsic viscosity ([η]) and light scattering techniques. The viscometric behaviour of the starting chitosans and of all depolymerization products follows an expected pattern. On the other hand, light scattering shows important differences among samples having identical [η], but obtained under different hydrolysis conditions. A tentative explanation is suggested for the discrepant responses.
So Kawaguchi - One of the best experts on this subject based on the ideXlab platform.
-
Light regime affects the seasonal cycle of Antarctic krill (Euphausia superba): impacts on growth, feeding, lipid metabolism, and maturity
Canadian Journal of Zoology, 2018Co-Authors: Flavia Höring, So Kawaguchi, Mathias Teschke, Lavinia Suberg, Bettina MeyerAbstract:Light regime is an important zeitgeber for Antarctic krill (Euphausia superba Dana, 1850), which seems to entrain an endogenous timing system that synchronizes its life cycle to the extreme light c...
-
KrillDB: A de novo transcriptome database for the Antarctic krill (Euphausia superba).
PloS one, 2017Co-Authors: Gabriele Sales, So Kawaguchi, Bettina Meyer, Bruce E. Deagle, Enrica Calura, Paolo Martini, Alberto Biscontin, Cristiano De Pittà, Chiara Romualdi, Rodolfo CostaAbstract:Antarctic krill (Euphausia superba) is a key species in the Southern Ocean with an estimated biomass between 100 and 500 million tonnes. Changes in krill population viability would have catastrophic effect on the Antarctic ecosystem. One looming threat due to elevated levels of anthropogenic atmospheric carbon dioxide (CO2) is ocean acidification (lowering of sea water pH by CO2 dissolving into the oceans). The genetics of Antarctic krill has long been of scientific interest for both for the analysis of population structure and analysis of functional genetics. However, the genetic resources available for the species are relatively modest. We have developed the most advanced genetic database on Euphausia superba, KrillDB, which includes comprehensive data sets of former and present transcriptome projects. In particular, we have built a de novo transcriptome assembly using more than 360 million Illumina sequence reads generated from larval krill including individuals subjected to different CO2 levels. The database gives access to: 1) the full list of assembled genes and transcripts; 2) their level of similarity to transcripts and proteins from other species; 3) the predicted protein domains contained within each transcript; 4) their predicted GO terms; 5) the level of expression of each transcript in the different larval stages and CO2 treatments. All references to external entities (sequences, domains, GO terms) are equipped with a link to the appropriate source database. Moreover, the software implements a full-text search engine that makes it possible to submit free-form queries. KrillDB represents the first large-scale attempt at classifying and annotating the full krill transcriptome. For this reason, we believe it will constitute a cornerstone of future approaches devoted to physiological and molecular study of this key species in the Southern Ocean food web.
-
A photographic documentation of the development of Antarctic krill (Euphausia superba) from egg to early juvenile
Polar Biology, 2014Co-Authors: Zhongnan Jia, Kerrie M. Swadling, Patti Virtue, So KawaguchiAbstract:Antarctic krill ( Euphausia superba ) is a key species in Antarctic marine ecosystems, as well as an important species in the Southern Ocean fishery. Here, we provide the first detailed photographic documentation of embryonic and larval development of Antarctic krill over a 5-month developmental period under controlled laboratory conditions. Developing embryos and larvae were photographed every 3 h and every 5 days, respectively. Our results indicated a developmental time of approximately 6 days for embryos and 138 days for larvae (0.5 °C). This study provided baseline biometry information for future investigations of Antarctic krill development under changing environmental conditions.
-
DNA as a dietary biomarker in Antarctic krill, Euphausia superba
Marine biotechnology (New York N.Y.), 2006Co-Authors: A. J. Passmore, So Kawaguchi, Simon N. Jarman, Kerrie M. Swadling, Andrew Mcminn, Stephen NicolAbstract:The diet of Antarctic krill (Euphausia superba) has been studied using a variety of techniques, but current methods still suffer from problems that are difficult to solve. This study examined an alternative approach utilizing DNA as a prey biomarker. Methods were developed for the preservation, extraction, and identification of prey DNA from krill collected in the field. Group-specific polymerase chain reaction (PCR) was used to amplify diatom prey (Phylum: Bacillariophyta) and the results from DNA clone libraries were compared with microscopic diet analysis. DNA analysis was superior to microscopy for prey detection. However, differences in prey relative abundance estimates between the two techniques suggested some bias in the DNA-based estimates. Quantification showed that large amounts of prey DNA had been successfully preserved and extracted. Overall the results suggest that the application of DNA-based diet analysis to krill warrants further investigation, particularly for prey that are difficult to study using other methods.
Gareth A. Pearson - One of the best experts on this subject based on the ideXlab platform.
-
A transcriptome resource for Antarctic krill (Euphausia superba Dana) exposed to short-term stress
Marine genomics, 2015Co-Authors: Maria João Fernandes Martins, Carlos M. Duarte, Asunción Lago-lestón, António Dos Anjos, Susana Agustí, Ester A. Serrão, Gareth A. PearsonAbstract:Euphausia superba is a keystone species in Antarctic food webs. However, the continued decrease in stock density raises concerns over the resilience and adaptive potential of krill to withstand the current rate of environmental change. We undertook a transcriptome-scale approach (454 pyrosequencing) as a baseline for future studies addressing the physiological response of krill to short-term food shortage and natural UV-B stress. The final assembly resulted in a total of 26,415 contigs, 39.8% of which were putatively annotated. Exploratory analyses indicate an overall reduction in protein synthesis under food shortage while UV stress resulted in the activation of photo-protective mechanisms.
-
Characterization of polymorphic microsatellite loci in the Antarctic krill Euphausia superba
BMC research notes, 2014Co-Authors: Rui Candeias, Sara Teixeira, Carlos M. Duarte, Gareth A. PearsonAbstract:Background The Antarctic krill, Euphausia superba is a pelagic crustacean, abundant in high-density swarms (10 000 – 30 000 ind/m2) with a circumpolar distribution and a key role in the food web of the Southern Ocean. Only three EST derived microsatellite markers have been used in previous genetic studies, hence we developed additional highly polymorphic microsatellite markers to allow robust studies of the genetic variability and population differentiation within this species.
Meng Zhou - One of the best experts on this subject based on the ideXlab platform.
-
aggregation and vertical migration behavior of Euphausia superba
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Meng Zhou, Ryan D DorlandAbstract:Aggregation and vertical migration behavior of Euphausia superba were studied in Marguerite Bay and its vicinity west of the Antarctic Peninsula using a vessel-mounted, Acoustic Doppler Current Profiler, and a Multiple Opening and Closing Nets and Environmental Sensing System, during the 2001 and 2002 fall US Southern Ocean GLOBEC project cruises. The kinematics of aggregation behavior of E. superba associated with diel migration is studied using observations of their abundance and swimming velocities: during the day, E. superba reduce their swimming at a depth of 250 m; and at night, they swim randomly at their cruising speed in the upper part of an aggregation near the surface, and coherently as schooling in the lower part of an aggregation. The causes for the aggregation behavior and vertical migration of krill are explored by examining the relationship with ice coverage and presence of predators. The motion of euphausiids is further analyzed in terms of kinetic energy and force balance, leading to new considerations of mathematical theories and models of aggregation behavior. The results show a diel variation of the energy demand for maintaining their locomotion. The horizontal scale of an aggregation is studied in conjunction with horizontal gradients of currents. Results indicate that the swimming capability of euphausiids determines the maintenance of an aggregation in the mesoscale circulation field.
