Immunogenic properties of mannose-containing ceramide tetrasaccharide from fresh-water bivalve, Hyriopsis schlegelii

Antiserum against GlcNAc beta 1----2Man alpha 1----3Man beta 1----4Glc beta 1----1Cer (MlOse4Cer), a mannolipid isolated from spermatozoa of the fresh-water bivalve Hyriopsis schlegelii, was elicited in rabbits by repeated injection of a mixture of hapten-bovine serum albumin with Freund's adjuvant. The specificity of the affinity-purified antibody obtained from the serum was based on two forms of enzyme-immunodetection of its binding to structurally related glycolipids, either adsorbed to microtiter plates or chromatographed on thin-layer plates. The purified antibody exhibited a significant cross-reactivity with GlcNAc beta 1----2Man alpha 1----3(Xyl beta 1----2)Man beta 1----4Glc beta 1----1Cer, (MIXOse5Cer) containing a core structure closely related to MlOse4Cer, but almost unrelated to other glycolipids. Distribution of MlOse4Cer and MlXOse5Cer in various bivalve and snail glycolipid extracts were screened in thin-layer immunobinding assays by using this purified specific antibody. The presence of the glycolipid antigens was limited to certain taxonomic orders of shellfish species.     

Colorimetry of the hepatopancreas in Antarctic krill,Euphausia superba

Summary Hepatopancreas color of freshly caught as well as starved Euphausia superba was examined by a chroma meter to express it quantitatively and compare it with plant pigment contents. There was a high positive correlation (r= 0.77) between plant pigment contents of hepatopancreas and the purity (vividness) of hepatopancreas color, and a negative correlation between the pigment contents and the luminosity (brightness) of the color. During the starvation experiment the purity decreased from 0.480 to 0.198 during the first 6 days in accordance with the decrease in plant pigment contents from 4.7 to 0.9 g krill^–1. An examination of hepatopancreas color by a chroma meter proved an easy and quantitative way of knowing the feeding condition of E. superba.     

Partial characterization of chitin degrading enzymes from two euphausiids,Euphausia superba and Meganyctiphanes norvegica

Summary Chitinase and N-acetyl--D-glucosaminidase have been demonstrated in Meganyctiphanes norvegica and in Euphausia superba and partly characterized. The enzymes from both species have broad pH-optima (maxima around pH 5.0) and temperature optima between 40 and 50°C. The enzymes are relatively stable; even at about 45°C half of the enzyme activity is retained after 30 min incubation. The presence of fluoride does not affeet enzymatic activity. Chitinase activity appears in three different molecular masses, N-acetyl--D-glucosaminidases in two different forms. pH and temperature optima, thermal stability and kinetic properties of the two enzymes are strikingly similar in the polar E. superba versus the boreal euphausiid M. norvegica. Enzyme activity in the lower temperature range is still high, whereas activation energies are low in both euphausiids. This suggests a functional adaptation to a low temperature range in seawater.     

Notes of food selection in the Antarctic krill, Euphausia superba

Analysis of the gut contents of Euphausia superba and of the phytoplankton composition in the area of the animals catchment served as a basis for answering the question whether or not E. superba is capable of food selection. It was found that the diatom Thalassiosira is preferred by E. superba as a food item and small pennate diatoms, Nitzschia, and Navicula are only tolerated as food. Other algae taxa, such as Tropidoneis, Dactyliosolen, Chaetoceros, and Gyrodinium, are clearly avoided. With respect to phytoplankton cell size, E. superba prefers cells with a length of 20–40 μm and cells larger than 70 μm are rejected. Trophic conditions only slightly affect the food selection of E. superba. Received: 4 September 1995/Accepted: 30 June 1996     

Some aspects of feeding in the Antarctic krill,Euphausia superba

Polar Biology - The interaction between feeding activity, swarming behaviour and vertical migration in Antarctic krill, Euphausia superba Dana, was examined by a combination of laboratory...     

Behavioral and Physiological Characteristics of the Antarctic Krill, Euphausia superba

The antarctic krill, Euphausia superba, is considered a successin the intensely seasonal environment of the Southern Oceanbecause of its abundance and central role as an important fooditem for many of the larger carnivores in the ecosystem. Thebehavioral and physiological characteristics that foster thissuccess are: (1) the ability to find concentrations of foodin several types of habitat and efficiently exploit whateverfood is available; (2) the close correspondence of the lifecycle with seasonal cycles of food availability; and (3) a combinationof physiological mechanisms that enable krill to survive thelong winter period of low food availability. We evaluated therelative importance of the following four major winter-overmechanisms that have been proposed for adult krill west of theAntarctic Peninsula. The three-fold reduction in metabolic rateis the most important winter-over mechanism for these adults,although lipid utilization and shrinkage also help satisfy energyrequirements in the winter. Alternate food sources did not appearto contribute significantly as a winter energy source. However,the extent, predictability and complexity of the ice cover ina region during winter may have a great influence on the relativeimportance of these winter-over mechanisms for different populations.Ice cover in the waters west of the Antarctic Peninsula is unpredictableand smooth surfaced when it occurs, providing the krill withlittle refuge from predation. In multi-year pack ice of theWeddell Sea, however, ice cover is predictable and extensive,and there is a complex undersurface that provides hiding places.In this multi-year ice, adult krill have been observed underthe ice feeding, whereas west of the Antarctic Peninsula mostadult krill are in the water column in the winter and are notfeeding. The balance between acquiring energy and avoiding predationmay be different in these two regions in the winter becauseof differences in predictability and complexity of the ice cover.     

Melatonin and its possible role in mediating seasonal metabolic changes of Antarctic krill, Euphausia superba

Melatonin, the chief secretory product of the vertebrate pineal gland is suspected to be a ubiquitous molecule principally involved in the transduction of photoperiodic information. Besides vertebrates, melatonin has been detected throughout phylogeny in numerous non-vertebrate taxa. In the present study, the occurrence of melatonin in Antarctic krill Euphausia superba and its possible role in mediating seasonal metabolic changes was evaluated. Melatonin was quantified by enzyme linked immunosorbent assay (ELISA) in high performance liquid chromatography (HPLC) purified extracts of eyestalks and hemolymph of krill sampled in the Lazarev Sea during the Antarctic winter and summer. In addition, oxygen uptake rates and the activities of the metabolic enzyme malate dehydrogenase (MDH) were recorded to assess the metabolic status of krill. Validation of melatonin measurements was carried out on the basis of three different extraction methods with parallel determination of melatonin by ELISA in crude extracts and in HPLC purified extracts, and after derivatization of melatonin under alkaline conditions in the presence of hydrogen peroxide. A significantly higher respiration rate and MDH activity was found in summer krill than in winter krill indicating that krill was in a state of reduced metabolic activity during winter. However, neither during winter nor during summer there were detectable melatonin concentrations in the visual system or hemolymph of krill. Based on these results, we question a mediating role of melatonin in the control of seasonal metabolic changes in Antarctic krill.     

Electrophoretic investigation of genetic variation in two krill species Euphausia superba and E. crystallorophias (Euphausiidae)

Summary Specimens of Euphausia superba and of E. crystallorophias from different locations were analyzed electrophoretically for protein variation. The present study extends previous genetic studies on E. superba by analyzing samples from the East Wind Drift and repeat samples from the Bransfield Strait, Elephant Island and the Weddell Sea. E. crystallorophias was collected in the Weddell Sea and around the Antarctic Peninsula in order to provide information on the breeding structure of the species in this region. For all loki taking all sampling sites together for both species except GPI in E. crystallorophias no significant deviation of phenotype distributions from random mating expectations was observed. Furthermore, the allele distributions in all polymorphic loci for both species were found to be homogeneous. Estimates of genetic distance between samples within each species are low (0.0001 to 0.0003 in E. superba and 0.0001 to 0.0002 in E. crystallorophias), and are consistent with results expected for samples from a single interbreeding population. Estimate of genetic distance between these two species was 0.9729. These results suggest that for each species specimens from all locations investigated in the Bransfield Strait and Weddell Sea belong to a single genetically homogeneous population. A possible mechanism for maintaining such homogeneity and the implications for fishery management are discussed.     

On the purification and characterization of exopeptidases from antarctic krill,Euphausia superba

• 1.1. Two carboxypeptidase-A type of enzymes and two carboxypeptidase-B type of enzymes effecting hydrolysis of Hipp-l-Phe and Hipp-l-Arg respectively, have been purified from E. superba using gel filtration, affinity chromatography and FPLC-anion exchange chromatography. In addition an aminopeptidase has been partly purified.
• 2.2. The carboxypeptidases had mol. wts of 27,000 (carboxypeptidase A) and 31,000 (carboxypeptidase B).
• 3.3. Carboxypeptidase A exhibited a broad pH optimum with a maximum at pH 5.5–6.5, whereas carboxypeptidase B had a more narrow pH-optimum with a maximum at pH 7. The aminopeptidase had an optimum at about pH 8.7.
• 4.4. The carboxypeptidases were inhibited by the chelating agent 1,10-phenanthroline.

     

Vertical distribution of two substages of stage Calyptopis I of Euphausia superba Dana,in South Orkneys Area

Summary Samples of Euphausia superba larvae at the Calyptopis I stage, taken in the upper 200 m near South Orkney Islands, have been analyzed discriminating early and advanced substages on the basis of the presence or absence of pleon segmentation, evidenced through the actual cuticle. A significant difference in pleon length between these forms is demonstrated, suggesting growth between them. Results show no difference between these in relation to their vertical distribution; supporting the view that developmental ascent has been already completed in the area. In both substages, a significant difference between night and day catches existed, but no evidence of diel migration was found in their vertical distributions.     

Ommochrome pigments in the eyes of Euphausia superba (Crustacea,Euphausiacea)

Summary Ommin and a xanthommatin-like ommochrome pigment have been extracted from the eyes of Euphausia superba, and identified by their absorbance spectra and redox reactions invarious solvents. The absorbance spectrum of ommin is relatively stable, but that of the xanthommatin pigment is sensitive to light, pH, and hydroxylamine. Both pigments are readily soluble in 2% digitonin. They are therefore likely contaminants of visual pigment extracts, and may consequently introduce artifacts into visual pigment characterizations. Microspectrophotometric measurements show that both pigments are components of the distal and proximal screening pigment granules in E. superba ommatidia.This paper is dedicated to the memory of Professor Mary Alice McWhinnie, to whom I owe a great debt of gratitude for her patient tutelage and the opportunity to participate in her Antarctic research, for the encouragement to pursue my own interests, and for her generous friendship. It was a cherished association which ended sadly with her untimely death in March, 1980. She will always be fondly remembered     

Population age structure in males and juveniles of the Antarctic Krill,Euphausia superba Dana

Summary Further results are reported on the age structure of populations of the Antarctic krill, using the age pigment lipofuscin. Study of the males shows a five-year adult life span as in females in an earlier study. Only a single age group was found in the juvenile stage.     

Preparation of two recombinant crustacean hyperglycemic hormones from the giant freshwater prawn, Macrobrachium rosenbergii, and their hyperglycemic activities

Crustacean hyperglycemic hormone (CHH) is released from the X-organ/sinus gland complex located in the eyestalks, and regulates glucose levels in the hemolymph. In the giant freshwater prawn (Macrobrachium rosenbergii), two cDNAs encoding different CHH molecules were previously cloned by other workers. One of these (Mar-CHH-2) was expressed only in the eyestalks, whereas the other (Mar-CHH-L) was expressed in the heart, gills, antennal gland, and thoracic ganglion, but not in the eyestalks. However, their biological activities had not yet been characterized. Therefore, in this study, recombinant Mar-CHH-2 (rMar-CHH-2) and Mar-CHH-L (rMar-CHH-L) were produced using an E. coli expression system, by expression in bacterial cells and recovery in the insoluble fraction. Thereafter, rMar-CHH-2 and rMar-CHH-L were subjected to refolding and were subsequently purified by reversed-phase HPLC. The rMar-CHH-2 and rMar-CHH-L thus obtained exhibited the same disulfide bond arrangements as those of other CHHs reported previously, indicative of natural conformation. In in vivo bioassay, rMar-CHH-2 showed significant hyperglycemic activity, whereas rMar-CHH-L had no effect. These results indicate that Mar-CHH-L does not function as a CHH, but may have some other, unknown function.     

Larval development of Euphausia superba Dana, 1852 and a phylogenetic analysis of the Euphausiacea

Literature data and new investigations by SEM of selected ontogenetic stages of the Antarctic Krill, Euphausia superba Dana, 1852 revealed morphological characters that are either missing in, or significantly changed towards, the adult. Besides adult features, such ontogenetic characters enabled us to propose a hypothesis of the phylogenetic relationships of and within the Euphausiacea on the basis of a computer aided cladistic analysis. These are of the form (Bentheuphausia amblyops + Euphausiidae = ('Thysanopoda' + Nematobrachion + Euphausiinae = (Meganyctiphanes norvegica + Euphausiini, new name + Nematoscelini, new name = (Nyctiphanes + Nematoscelina, new name)))). From this analysis the taxon names 'Euphausiina', 'Nematoscelini', and 'Nematoscelina' are introduced for in-groups of the taxon Euphausiacea as representing monophyletic units. The position of a set of ontogenetic characters remains relatively uncertain due to the still unknown larval development of Bentheuphausia amblyops (G. O. Sars, 1883).     

Euphausiid visual pigments. The rhodopsins of Euphausia superba and Meganyctiphanes norvegica (Crustacea, Euphausiacea)

The rhabdoms of Euphausia superba contain one digitonin-extractable rhodopsin, lambda max 485 nm. The rhodopsin undergoes unusual pH- dependent spectral changes: above neutrality, the absorbance decreases progressively at 485 nm and rises near 370 nm. This change is reversible and appears to reflect an equilibrium between a protonated and an unprotonated form of the rhodopsin Schiff-base linkage. Near neutral pH and at 10 degrees C, the rhodopsin is partiaLly converted by 420-nm light to a stable 493-nm metarhodopsin. The metarhodopsin is partially photoconverted to rhodopsin by long-wavelength light in the absence of NH2OH; in the presence of NH2OH, it is slowly converted to retinal oxime and opsin. The rhodopsin of Meganyctiphanes norvegica measured in fresh rhabdoms by microspectrophotometry has properties very similar to those of the extracted rhodopsin of E. superba. Its lambda max is 488 nm and it is partially photoconverted by short wavelength irradiation to a stable photoconvertible metarhodopsin similar to that of E. superba. In the presence of light and NH2OH, the M. norvegica metarhodopsin is converted to retinal oxime and opsin. Our results indicate that previous determinations of euphausiid rhodopsin absorbance spectra were incorrect because of accessory pigment contamination.     

Stable isotope composition ({delta}13C and {delta}15N) of larval krill, Euphausia superba, and two of its potential food sources in winter

Natural abundances of ¹³C (     

Laboratory observations of moulting,growth and maturation in Antarctic krill (Euphausia superba Dana)

Summary Observations of intermoult period, growth and maturation were made on krill which were transported from Antarctic waters and maintained in the laboratory in Australia over a three year period. The mean intermoult period (IP) for each of 10 specimens, with initial body lengths of 24.7=46.8 mm, kept at -0.5° C varied from 22.0 to 29.8 days (overall mean = 26.6 days). These measurements of IP are significantly longer than those obtained in some previous studies. Differences in experimental temperatures, light, body sizes and growth patterns of the specimens between studies are unlikely to be causes of these dissimilar results. The pattern of changes in body length (BL) varies from one individual to the next. The greatest increase in BL over a series of 4–5 moults ranged from 0.024 to 0.070 mm/day, which is equivalent to 0.0020 to 0.0086/day in body weight, assuming exponential growth. This maximum growth rate is about half the rate predicted from the growth scheme of Mauchline (1980) for wild krill. Comparison of growth data for other euphausiids suggests that Mauchline's scheme produces anomalous growth rate. The slower growth rate observed in the present study would extend the estimated life span of krill from 3–4 years, as calculated by Mauchline (1980), to 4–7 years. If krill undergo body shrinkage during the Antarctic winter the estimated life span might be even longer. Examination of the external sexual characters of moults showed both progression and regression of maturity stage in association with changes in BL.     

2016年南极斯科舍海南极大磷虾种群结构的时空变化

斯科舍海是南极大磷虾资源分布最为密集的海域,也是磷虾的传统渔场,但该海域磷虾种群结构存在较为显著的年际、季节性与区域性差异.为了解该海域磷虾种群动态,本研究利用2016年1—9月由渔业调查随机收集的样本,对该海域磷虾种群结构的时空变动进行了分析.结果表明: 各月磷虾性比存在显著的差异,1—5月雌性明显占优,而6—9月则呈现相反的趋势.1—9月期间,仅1月出现幼体,且雌性成体的比例与2月相当,占比超过了40%;3—5月,雌性未成体的比例均超过了50%,而雌性成体的比例开始逐月下降;6—8月,雄性未成体的比例达到峰值;9月,雌性未成体的比例显著增加,而雄性成体的比例呈下降趋势.在布兰斯菲尔德海峡内,2—5月,雌性未成体的比例超过一半;1月,乔治王岛东北水域已排卵个体的比例(25.6%)显著高于其他个体,雌性临产个体的比例也较高;6—9月,南乔治亚岛东北水域雄性成体的比例约占一半,雌性成体的比例极低.性成熟度组成显示,1—2月为磷虾产卵盛期,而产卵场出现在乔治王岛东北水域以及布兰斯菲尔德海峡.