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PubMed2005

Enhancement of enzymatic digestion of Antarctic krill and successive extraction of selenium organic compounds by ultrasound treatment.

In a previous work we described the isolation of selenium organic species from Antarctic krill after enzymatic hydrolysis. In this paper we present the results of the influence of ultrasonication on the enzymatic treatment and the successive isolation of selenomethionine. We showed that ultrasound-assisted enzymatic digestion leads to quantitative release of selenium in the soluble fraction and recovery of selenomethionine from the krill protein within a time 2 orders of magnitude shorter. The solubilised sample was analysed by size-exclusion chromatography and the selenomethionine content was quantified by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. In total, 99% of the selenomethionine in the krill hydrolysate was recovered from the chromatographic fractions. It corresponds to 35% of the total selenium content in Antarctic krill. Monitoring by microscopy of the changes in the structure of the krill samples during ultrasonication suggested that the enhancement of the ultrasound-assisted enzymatic reaction was mainly due to decrease of mass transfer limitations. A reference experiment for ultrasound-assisted enzymatic digestion of cell-free protein in a homogeneous system does not exclude direct influence of the ultrasound energy on the enzyme-substrate interaction.

Animals↗
PubMed2005

New locality records for third-stage larvae of Anisakis simplex (sensu lato) (Nematoda: Ascaridoidea) in euphausiids Euphausia pacifica and Thysanoessa raschii from Prince William Sound, Alaska.

Five euphausiid species (n=41,037) were collected in October 1997 from Prince William Sound, Alaska, and examined for parasites. New locality records are claimed for third-stage larvae (L3) of whaleworm Anisakis simplex (sensu lato) in two (0.019%) of 10,437 Thysanoessa raschii, and in one (0.013%) of 7,443 Euphausia pacifica. The L3 were about 19.5, 21.3 and 30.5 mm long. L3 were absent from 8,026 T. inermis, 10,302 T. longipes and 4,829 T. spinifera collected at the same time, and from 6,648 euphausiids representing the five species collected in July 1998. No individual harboured more than one parasite-a whaleworm L3, the ellobiopsid Thalassomyces fagei, a trypanorhynchid (tetrarhynchid) cestode (probably Nybelinia sp.), or a possible rhizocephalan. Controversy regarding the number of moults that occur in the egg of marine ascaridoids is discussed briefly.

Alaska↗
PubMed2004

A new approach to the solution of the linear mixing model for a single isotope: application to the case of an opportunistic predator.

Mixing models are used to determine diets where the number of prey items are greater than one, however, the limitation of the linear mixing method is the lack of a unique solution when the number of potential sources is greater than the number (n) of isotopic signatures +1. Using the IsoSource program all possible combinations of each source contribution (0-100%) in preselected small increments can be examined and a range of values produced for each sample analysed. We propose the use of a Moore Penrose (M-P) pseudoinverse, which involves the inverse of a 2x2 matrix. This is easily generalized to the case of a single isotope with (p) prey sources and produces a specific solution. The Antarctic leopard seal (Hydrurga leptonyx) was used as a model species to test this method. This seal is an opportunistic predator, which preys on a wide range of species including seals, penguins, fish and krill. The M-P method was used to determine the contribution to diet from each of the four prey types based on blood and fur samples collected over three consecutive austral summers. The advantage of the M-P method was the production of a vector of fractions f for each predator isotopic value, allowing us to identify the relative variation in dietary proportions. Comparison of the calculated fractions from this method with 'means' from IsoSource allowed confidence in the new approach for the case of a single isotope, N.

Animals↗
PubMed2006

Hierarchical patch dynamics and animal movement pattern.

In hierarchical patch systems, small-scale patches of high density are nested within large-scale patches of low density. The organization of multiple-scale hierarchical systems makes non-random strategies for dispersal and movement particularly important. Here, we apply a new method based on first-passage time on the pathway of a foraging seabird, the Antarctic petrel (Thalassoica antarctica), to quantify its foraging pattern and the spatial dynamics of its foraging areas. Our results suggest that Antarctic petrels used a nested search strategy to track a highly dynamic hierarchical patch system where small-scale patches were congregated within patches at larger scales. The birds searched for large-scale patches by traveling fast and over long distances. Once within a large-scale patch, the birds concentrated their search to find smaller scale patches. By comparing the pathway of different birds we were able to quantify the spatial scale and turnover of their foraging areas. On the largest scale we found foraging areas with a characteristic scale of about 400 km. Nested within these areas we found foraging areas with a characteristic scale of about 100 km. The large-scale areas disappeared or moved within a time frame of weeks while the nested small-scale areas disappeared or moved within days. Antarctic krill (Euphausia superba) is the dominant food item of Antarctic petrels and we suggest that our findings reflect the spatial dynamics of krill in the area.

Animal Migration↗
PubMed2004

Organization of the mitochondrial genome of Antarctic krill Euphausia superba (Crustacea: Malacostraca).

We determined the nearly complete DNA sequence of the mitochondrial genome of Antarctic krill Euphausia superba (Crustacea: Malacostraca), one of the most ecologically and commercially important zooplankters in Antarctic waters. All of the genome sequences were purified by gene amplification using long polymerase chain reaction (PCR), and the products were subsequently used as templates for either direct sequencing using a primer-walking strategy or nested PCR with crustacea-versatile primers. Although we were unable to determine a portion of the genome owing to technical difficulties, the sequenced position, 14,606 bp long, contained all of the 13 protein-coding genes, 19 of the 22 transfer RNA genes, and the large subunit as well as a portion of the small subunit ribosomal RNA genes. Gene rearrangement was observed for 3 transfer RNA genes (tRNACys, tRNATyr, and tRNATrp) and the 2 leucine tRNA genes.

Amino Acid Sequence↗
PubMed2006

DNA as a dietary biomarker in Antarctic krill, Euphausia superba.

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.

Animals↗
PubMed2006

Gymnodinioides pacifica, n. sp., an exuviotrophic ciliated protozoan (Ciliophora, Apostomatida) from euphausiids of the Northeastern Pacific.

A new species of apostome ciliate, Gymnodinioides pacifica n. sp. from the euphausiid Euphausia pacifica is described. The ciliated protozoan encysts on the setae of the appendages, telson and antennae. It excysts and enters the exoskeleton of the host after moulting, where it feeds on exuvial fluid. The phoront and trophont stages of this ciliate are described. The ciliature of the trophont has the following characteristics that distinguish it from the other species of Gymnodinioides: (1) a short kinety 9a (ciliary row 9a or K9a), approximately half of the length of falciform field 8, that extends from the anterior end of the cell posteriorly to the level of K1, (2) a straight K5a, perpendicular to K5b, K6, and K7, and (3) two distinct bands of kineties, K9b-K5b and K4-K1. In addition to those on the host E. pacifica, phoront cysts of similar shape were observed on Thysanoessa spinifera, T. gregaria, T. inspinata, T. longipes, and Nematoscelis difficilis. High prevalence rates were recorded (83%) for these apostome cysts on E. pacifica and T. spinifera during summer collections from the Oregon and Washington coasts. Additionally, we report other apostome ciliate symbionts of euphausiids, including Phtorophrya sp., which preys on apostomes in the genus Gymnodinioides.

Animals↗
PubMed2005

Occurrence of organochlorine pesticides (OCPs) and their enantiomeric signatures, and concentrations of polybrominated diphenyl ethers (PBDEs) in the Adélie penguin food web, Antarctica.

Concentrations and enantiomeric signatures of organochlorine pesticides were determined in Antarctic krill, emerald rockcod and Adélie penguin from the Ross Sea, Antarctica. HCB and DDTs were prevalent contaminants in penguin eggs. The highest concentrations of SigmaHCHs (1.35 +/- 0.72 ng/g) were found in the rockcod muscle, where gamma-HCH (1.23 +/- 0.67 ng/g) was the principal isomer. The ratio gamma-HCH/alpha-HCH was evaluated. Enantioselective gas chromatography was used for the evaluation of enantiomeric fractions (EFs) for alpha-HCH and oxychlordane. An increase of 14% in the (+)alpha-HCH enantiomer was found from krill through penguin, suggesting the enantioselective biotransformation increased proportionately with trophic level. Polybrominated diphenyl ethers (PBDEs) were measured and their concentrations were 5.6 +/- 1.12, 5.81 +/- 2.32, 4.57 +/- 0.17 and 3.06 +/- 3.27 ng/g lipids in krill, rockcod muscle, rockcod homogenate and penguin eggs, respectively. The detection of BDE28, BDE47, BDE99 and BDE100 in Antarctic organisms confirmed their global transport and distribution; the detection of lower brominated congeners suggested a potential long-range transport.

Animals↗
PubMed2005

Distribution of elements binding to molecules with different molecular weights in aqueous extract of Antarctic krill by size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry.

The distribution of silver, arsenic, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, selenium and zinc binding to species with different molecular weight in aqueous extract of krill was studied by on-line size-exclusion chromatography (SEC)/inductively coupled plasma mass spectrometry (ICP-MS). The extract was fractionated in three fractions with different molecular weight (MW) ranges (>20,000 relative molecular mass (rel. mol. mass), 2000-20,000 rel. mol. mass and <2000 rel. mol. mass), which were further analyzed by SEC with columns having different optimum fractionation ranges in order to obtain more detailed information about the MW distribution of the elements. Various distribution profiles for the target elements among different MW ranges were observed. The results obtained indicated that manganese, zinc, silver, cadmium and lead species were mostly distributed in the higher MW range (>20,000 rel. mol. mass). In the case of chromium, iron, cobalt, arsenic and selenium, most of them bind to species with lower MW (<2000 rel. mol. mass). Only copper and nickel species was predominantly present in middle MW range (2000-20,000 rel. mol. mass). Further speciation of arsenic compounds in the small MW fraction was carried out with anion exchange chromatography (AEC) coupled with ICP-MS. The results showed that the dominant arsenic species in this fraction is As(III) (63% of extractable arsenic), while As(V) (13%) and two unknown arsenic species (19% and 5%, respectively) are present in lower amounts.

Animals↗
PubMed2006

Computational determination of refractive index distribution in the crystalline cones of the compound eye of Antarctic krill (Euphausia superba).

In order to understand how a compound eye channels light to the retina and forms an image, one needs to know the refractive index distribution in the crystalline cones. Direct measurements of the refractive indices require sections of fresh, unfixed tissue and the use of an interference microscope, but frequently neither is available. Using the eye of the Antarctic krill Euphausia superba (the main food of baleen whales) we developed a computational method to predict a likely refractive index distribution non-invasively from sections of fixed material without the need of an interference microscope. We used a computer model of the eye and calculated the most realistic spatial distribution of the refractive index gradient in the crystalline cone that would enable the eye to produce a sharp image on the retina. The animals are known to see well and on the basis of our computations we predict that for the eyes of the adult a maximum refractive index of 1.45-1.50 in the centre of the cone yields a better angular sensitivity and light absorption in a target receptor of the retina than if N(max) were 1.55. In juveniles with a narrower spatial separation between dioptric structures and retina, however, an N(max) of 1.50-1.55 gives a superior result. Our method to determine the most likely refractive index distribution in the cone without the need of fresh material and an interference microscope could be useful in the study of other invertebrate eyes that are known to possess good resolving power, but for a variety of reasons are not suitable for or will not permit direct refractive index measurements of their dioptric tissues to be taken.

Animals↗
PubMedDate not supplied

Multi-trial biomarker approach in Meganyctiphanes norvegica: a potential early indicator of health status of the Mediterranean "whale sanctuary.".

The aim of this study was to propose a suite of biomarkers (BPMO activity, NADPH-cytocrome c reductase, NADH-ferricyanide reductase. esterases, porphyrins, vitellogenin and zona radiata proteins) and residue levels (organochlorines, PAHs and heavy metals) in the zooplanktonic euphausiid Meganyctiphanes norvegica as a potential multi-disciplinary diagnostic tool for assessment of the health status of the Mediterranean "whale sanctuary". Very little difference in BPMO was detected between sites, with values ranging from 0.75 to 2.68 U.A.F./mg prot/h. On the other hand larger differences between sites were found for reductase activities. Esterases (AChE), porphyrins (Copro-, Uro-, Proto-porphyrins) vitellogenin and zona radiata proteins were also detectable in this zooplanctonic species. Hg showed mean levels of 0.141 ppm d.w., Cd 0.119 ppm d.w. and Pb 0.496 ppm d.w. Total PAHs ranged from 860.7 to 5,037.9 ng/g d.w., carcinogenic PAHs from 40.3 to 141.7 ng/g d.w., HCB from 3.5 to 11.6 ng/g d.w., DDTs from 45.3 to 163.2 ng/g d.w. and the PCBs from 84.6 to 210.2 ng/g d.w.

Animals↗
PubMed2002

Characterization of proteinases from Antarctic krill (Euphausia superba).

Fractions of three trypsin-like proteinases, TL I, TL II, and TL III, a chymotrypsin-like proteinase, CL, two carboxypeptidase A enzymes, CPA I and CPA II and two carboxypeptidase B enzymes, CPB I and CPB II, from Antarctic krill (Euphausia superba) have been characterized with respect to purity by the means of capillary electrophoresis, CE, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The masses of the trypsin-like and chymotrypsin-like proteinases were determined to be 25,020, 25,070, 25,060, and 26,260Da for TL I, TL II, TL III, and CL, respectively. The masses of the CPA enzymes are likely 23,170 and 23,260Da, whereas the CPB enzyme masses likely are 33,730 and 33,900Da. The degradation efficiency and cleavage pattern of the trypsin-like proteinases were studied with native myoglobin as a model substrate using CE, MALDI-TOF-MS, and nanoelectrospray mass spectrometry (nESI-MS). The degradation efficiency of the trypsin-like proteinases was found to be approximately 12 and 60 times higher compared to bovine trypsin at 37 degrees C and 1-3 degrees C, respectively. All three fractions of trypsin-like proteinases showed a carboxypeptidase activity in combination with their trypsin activity.

Animals↗
PubMed2002

Notothenioid fish, krill and phytoplankton from Antarctica contain a vitamin E constituent (alpha-tocomonoenol) functionally associated with cold-water adaptation.

The vitamin E (VE) content of tissues from the Antarctic notothenioid fish, Chaenocephalus aceratus, Champsocephalus gunnari and Gobionotothen gibberifrons, and extracts of Antarctic krill Euphausia superba and phytoplankton collected from the Antarctic Peninsula was examined. Included in the VE composition was a newly described 'marine-derived' tocopherol (MDT), an unsaturated-isoprenoid derivative of alpha-tocopherol, that is attributed to enhancing antioxidant protection of cellular lipids at low temperature. MDT was found to co-exist with alpha-tocopherol in all Antarctic samples, ranging from 2.8 to 22.3% of the total VE composition. The highest level of VE was found in the liver of G. gibberifrons (VE=416.7 pmol/mg wet tissue) although this tissue had a low MDT composition (7.7%), whereas the greatest MDT composition was measured in the liver of C. gunnari (MDT=22.3%). In notothenioids, the pectoral adductor muscle, which has a high density of mitochondria, contained higher levels of VE than white myotomal muscle, but differences in MDT composition were small. Phytoplankton and krill also contained MDT, which supports the contention that MDT is obtained directly from the primary food chain. Our finding of MDT in Antarctic organisms is consistent with its putatively adaptive function to enhance antioxidant protection in coldwater metabolism.

Adaptation, Physiological↗
PubMed2003

Fatty acids of astaxanthin esters in krill determined by mild mass spectrometry.

Krill is a major source of astaxanthin, which has strong antioxidant activity. Fractions with astaxanthin monoesters and diesters of Antarctic krill Euphausia superba were isolated. Astaxanthin esters were separated by C18-HPLC depending on the number of carbons and double bonds of esterified fatty acid(s). Small amounts of other lipids remained in the samples, but relative molecular masses of carotenoid esters could be measured by field desorption mass spectrometry without fragmentation and interference from contaminant lipids. The fatty acids were determined by calculation of difference between astaxanthin and astaxanthin esters. Only five kinds of fatty acids, dodecanoate, tetradecanoate, hexadecanoate, hexadecenoate and octadecenoate, were detected. Fast atom bombardment mass spectrometry and secondary ion mass spectrometry showed similar spectra. The fatty acid composition in astaxanthin esters was different from those in krill lipids. Therefore, determination of fatty acids in carotenoid esters by a combination of HPLC elution profile and mild mass spectrometry is found to be a useful tool.

Animals↗
PubMed2003

Antarctic marine bacterium Pseudoalteromonas sp. 22b as a source of cold-adapted beta-galactosidase.

The marine, psychrotolerant, rod-shaped and Gram-negative bacterium 22b (the best of 41 beta-galactosidase producers out of 107 Antarctic strains subjected to screening), classified as Pseudoalteromonas sp. based on 16S rRNA gene sequence, isolated from the alimentary tract of Antarctic krill Thyssanoessa macrura, synthesizes an intracellular cold-adapted beta-galactosidase, which efficiently hydrolyzes lactose at 0-20 degrees C, as indicated by its specific activity of 21-67 U mg(-1) of protein (11-35% of maximum activity) in this temperature range, as well as k(cat) of 157 s(-1), and k(cat)/K(m) of 47.5 mM(-1) s(-1) at 20 degrees C. The maximum enzyme synthesis (lactose as a sufficient inducer) was observed at 6 degrees C, thus below the optimum growth temperature of the bacterium (15 degrees C). The enzyme extracted from cells was purified to homogeneity (25% recovery) by using the fast, three-step procedure, including affinity chromatography on PABTG-Sepharose. The enzyme is a tetramer composed of roughly 115 kDa subunits. It is maximally active at 40 degrees C (190 U mg(-1) of protein) and pH 6.0-8.0. PNPG is its preferred substrate (50% higher activity than against ONPG). The Pseudoalteromonas sp. 22b beta-galactosidase is activated by thiol compounds (70% rise in activity in the presence of 10 mM dithiotreitol), some metal ions (K(+), Na(+), Mn(2+)-40% increase, Mg(2+)-15% enhancement), and markedly inactivated by pCMB and heavy metal ions, particularly Cu(2+). Noteworthy, Ca(2+) ions do not affect the enzyme activity, and the homogeneous protein is stable at 4 degrees C for at least 30 days without any stabilizers.

Antarctic Regions↗
PubMed2006

Modelling Southern Ocean ecosystems: krill, the food-web, and the impacts of harvesting.

The ecosystem approach to fisheries recognises the interdependence between harvested species and other ecosystem components. It aims to account for the propagation of the effects of harvesting through the food-web. The formulation and evaluation of ecosystem-based management strategies requires reliable models of ecosystem dynamics to predict these effects. The krill-based system in the Southern Ocean was the focus of some of the earliest models exploring such effects. It is also a suitable example for the development of models to support the ecosystem approach to fisheries because it has a relatively simple food-web structure and progress has been made in developing models of the key species and interactions, some of which has been motivated by the need to develop ecosystem-based management. Antarctic krill, Euphausia superba, is the main target species for the fishery and the main prey of many top predators. It is therefore critical to capture the processes affecting the dynamics and distribution of krill in ecosystem dynamics models. These processes include environmental influences on recruitment and the spatially variable influence of advection. Models must also capture the interactions between krill and its consumers, which are mediated by the spatial structure of the environment. Various models have explored predator-prey population dynamics with simplistic representations of these interactions, while others have focused on specific details of the interactions. There is now a pressing need to develop plausible and practical models of ecosystem dynamics that link processes occurring at these different scales. Many studies have highlighted uncertainties in our understanding of the system, which indicates future priorities in terms of both data collection and developing methods to evaluate the effects of these uncertainties on model predictions. We propose a modelling approach that focuses on harvested species and their monitored consumers and that evaluates model uncertainty by using alternative structures and functional forms in a Monte Carlo framework.

Animals↗