Diapause of Cyclops vicinus (Uljanin) in Lake Søbygård: Indication of a Risk-spreading Strategy

Cyclops vicinus is reported to enter summer diapause triggered by day length in order to survive food scarcity and fish predation. Development ceases and the fourth or fifth copepodid stages persist in the sediment for several weeks. In Lake Søbygård, however, a small eutrophic lake in Denmark, C. vicinus is found in the sediment as well as in the open water throughout the year. We performed laboratory experiments to elucidate the life cycle strategy of this population. In order to find the factors that induce diapause we tested the influence of food composition and light regime on the proportion of copepods entering diapause. Further we examined the diapause pattern of the offspring from diapausing and non-diapausing parents to see whether the co-occurrence of diapausing and non-diapausing copepods results from genetic differentiation within the population. In all experiments some of the copepods developed directly into adults, while others remained at the fourth or fifth copepodid stage and displayed diapause features. The proportion of copepods that developed directly into adults was influenced by food supply. Fewer individuals entered diapause when they received a mixed diet of algae and ciliates or algae, ciliates and seston compared with a pure algal diet. The response to light was different than described in literature: about 30% of the copepods entered diapause under dark conditions, and the diapause frequency was not higher when copepods had been exposed to continuous light. The offspring from diapausing parents showed no higher tendency to enter diapause than the offspring of non-diapausing parents, indicating no genetic differentiation. We conclude that diapause in C. vicinus represents a risk-spreading strategy, modified by food. The simultaneous production of diapausing and non-diapausing offspring ensures survival under harsh conditions; the influence of the food supply on the proportion of individuals entering diapause may adjust the population to the actual environmental condition. This flexible life cycle strategy might contribute to the exclusive dominance of C. vicinus in Lake Søbygård.     

Summer feeding strategy of the little auk (Alle alle) from Bjørnøya, Barents Sea

Summer food of the little auks nesting on Bjornoya consisted of large copepods, decapod larvae and pelagic amphipods. Food items of 4–6?mm constituted the most common prey size fraction. This prey size range appears to be optimal (most profitable) with regard to the balance between mean individual mass and density of items in the surface layers of the sea. Little auks from Bjørnøya only sporadically take the abundant copepod Calanus finmarchicus (2–3.5?mm in length) but select the much less abundant and larger Calanus glacialis (3–6?mm).RID="ID=" Acknowledgements The authors would like to thank Dr. Monika Normant from the University of Gdansk for her assistance with caloric measurments, and Lech Illiszko and Adam Wajrak for their help with the fieldwork on Bj&;oslash;rn&;oslash;ya.RID="ID=" Correspondence to J. M. We&;cedil;s&;lstrok;awski     

Modelling the recovery of hypertrophic L. Glumsø (Denmark)

Diversion of sewage from L. Glumsø reduced phosphorus loading from 6.0 g P.m^–2.yr^–1 to 1.6 g P.m^–2.yr^–1. Chlorophyll levels during summer were reduced from 6–800 mg Chl.m^–3 to about 200 mg Chl.m^–3 mainly by extended periods with phosphorus limitation. Internal phosphorus loading was significant in the first 2 years after nutrient reduction. Predictions of the recovery were made by both simple, empirical models and with complex, dynamic model versions. The actual responses of L. Glumsø were compared with both previously published predictions and predictions made with improved model versions. Objective functions of 0.18 and global correlation coefficients of 0.89 could be achieved.     

降脂蛋白(a)研究

脂蛋白(a)[Lp(a)]是由载脂蛋白(a)(apo(a))与载脂蛋白B100(apoB100)通过共价键连接的脂蛋白。高血浆水平Lp(a)是心血管疾病的独立风险因子,Lp(a)的血浆水平主要受遗传因素调控,主要有LPA[lipoprotein,Lp(a)]基因的三环结构域kringle IV/2拷贝数和单核苷酸多态性(SNP)。欧洲动脉粥样硬化协会(EAS)和美国心脏病协会(AHA)建议对于高Lp(a)的人群应当考虑降高Lp(a)的治疗。目前已有多种降高Lp(a)的药物和方法,如血浆分离置换法、雌激素治疗、反义核苷酸治疗、类法尼醇X核内受体(farnesoid X receptor,FXR)激动治疗等,但应用于临床的降高Lp(a)的药物和方法依然缺乏。本文拟就降Lp(a)的药物和方法进展情况进行综述。     

Lichen species from the northeastern shore of Sørkapp Land (Svalbard)

In July and August 2005, the occurrence, distribution, and ecology of lichen species were studied in northeastern Sørkapp Land region (Spitsbergen) in areas undergoing the process of rapid glacier recession over the past century. A total of 48 lichen species were observed and two species (Acarospora heppii and Pycnothelia papillaria) are newly reported for the Svalbard archipelago.     

脂蛋白(a)合成的调节

脂蛋白(a) ［ LP(a)］是一种与低密度脂蛋白(LDL)结构极其相似的脂蛋白,它由LDL脂质核心、载脂蛋白B100(apoB100)及特异性的成分载脂蛋白(a)［ apo(a)］组成. 大量的研究表明,高LP(a)是动脉粥样硬化独立的危险因素.而LP(a)在血浆中的水平及致病能力取决于其合成的速率及其颗粒的大小. 因此, 如何抑制LP(a)合成,进而从源头减少LP(a) 的血浆水平,对动脉粥样硬化的防治具有重要的意义.本文就当前关于影响LP(a)合成的环节及相关机制进行综述, 从而为降LP(a)药物的研究提供新的视角.     

The Høylandet area – patterns and processes of a pristine boreal-subalpine ecosystem – a synopsis

The research activities on soil–freshwaterinteractions and freshwater biotic structure andprocesses in the Høylandet area during the years 1986–89are presented in this issue ofHydrobiologia. The 9 papers cover a range of topicsfrom physiochemical gradients and processes in soilsand freshwaters to selected aspects of freshwaterbiotic community structure and temporal variability.This synopsis aims (a) to present an overview of majorfindings, (b) to interpret the results in the contextof air pollution effects and (c) to outlinesuggestions for future research activities inHøylandet. The area has a sub-oceanic climate varyingfrom 1100 to 2200 mm of precipitation normallyoriginating from unpolluted airmasses from the NorthAtlantic. It is chemically dominated by sea salts, haslow concentrations and low deposition of mineralacids. The catchment geology is variable and complexand consists mainly of various granites and gneisses.The soils are undisturbed ancient soils,primarily iron podzols associated with forests, orintact histosols with strong organic characterassociated with mires, often quite acidic.They are sensitive because occurrence of predominantlyinsoluble unstable Al-complexes may leach out ifexposed to anthropogenically acidified soil drainagewater and turn up as toxic inorganic aqueous Al insurface runoff. Small amounts of locally generatednitrogen compounds are mostly retained in thecatchment. The water qualities of these Høylandetsites are run by inputs of sea salts, hydrologicalprocesses including dilution of the base flow, orlateral surface or overland flow and in-catchmentprocesses. Relative to affected areas, it appears thatthe inputs and catchment processes are in balance,i.e., that the inputs of strong acid anions, hydrogenions and sea salts are equilibrated by internalweathering and other processes and integrated withinapparently intact biogeochemical cycles. The overallresult is that these soils remain a net source ofalkalinity to the runoff. These results are confirmedby regional studies of water quality both at low andhigh flow which show that the humus and ionic contentof the water decreased with elevation, headwatersbeing more dominated by sea salts and dilutionprocesses. Excess sulphate concentrations are low, andfew if any sites appear anthropogenically acidified,the most acid pHs reflecting presence of natural weakorganic acids.The resulting surface water quality allows a diverseaquatic fauna and flora with representatives of manyacid-sensitive groups. The fish fauna consists ofself-reproducing salmonid populations with normaldemography and ecological interactions. Despite highin-lake mortality, both brown trout and Arctic charrexhibited normal age-class compositions, with noindication of the recruitment failure or highpost-spawning mortality commonly observed inacid-stressed situations. The zooplankton and benthos in the lakesare inhabited by populations of several acid sensitivespecies, like Daphnia spp and Gammaruslacustris, and with dominance of mayfly species ofthe genus Baetis in the stream fauna. Thediatom flora includes many species which are rare orabsent in acidified waters. The observed gradients indiversity and biomass seem dominated by localenvironmental conditions which reflect natural ratherthan man-made processes. The pristine nature of thearea also emerges from the paleoecological studies inLake Røyrtjønna which show that the low acidity ofthis lake evironment has persisted from preindustrialtill present times. Suggestion for future researchactivities in Høylandet are outlined.     

What Is (Not) a Baboon?

The term “baboon” is the common name used for a subset of terrestrial Cercopithecines with large bodies and protruding snouts. Although the application of the term has changed considerably over the years, we argue that common names, such as “baboon,” should reflect the current state of phylogenetic knowledge. This practice promotes a broader understanding of taxonomic diversity that can impact decisions related to ecotourism, wildlife management, and conservation. Thus, we argue that “baboon” should be used only for members of the genus Papio.     

A 14-year study of habitat use and diet of brown trout (Salmo trutta) and Arctic charr (Salvelinus alpinus) in Lake Atnsjøen, a subalpine Norwegian lake

To reveal the mechanisms of sedimental H₂S accumulation, annual investigations on sedimental environments were conducted in two temperate estuarine lagoons. The lagoons, Gamo and Idoura (Japan), have similar shapes, locations, and topographical properties but different degrees of H₂S accumulation. Water stagnation causes a high phytoplankton biomass (Chl. a; 26–52 g l^–1) in the inner Gamo Lagoon. Gamo Lagoon sediment was characterized by high bounded sulfides (bounded Smainly FeS) and H₂S contents, and low C/N ratios (mean = 10.4) and iron (reactive Fe²⁺ and total Fe) contents. H₂S was not detected in Idoura Lagoon where phytoplankton biomass was much lower (Chl. a; 0.6–4 g l^–1). Idoura Lagoon sediment had high C/N ratios (mean=17.9) and high iron contents. The C/N ratio difference implies that organic matter in Gamo Lagoon originates mainly from more decomposable phytoplankton, while organic matter in Idoura Lagoon derives mainly from terrestrial vascular plants with lower decomposability. The excess loading of phytoplanktonic detritus in Gamo accelerates sedimentary microbial activity, including sulfate reduction (i.e., H₂S production). High Fe²⁺and low bounded S contents in Idoura sediment indicate a high chemical buffering capacity toward H₂S. In contrast, almost all Fe²⁺ in Gamo Lagoon had already reacted with H₂S as FeS. H₂S accumulation in Gamo Lagoon is caused by low sedimentary chemical buffering capacity toward H₂S, as well as higher microbial H₂S production, caused by the excess loading of phytoplanktonic detritus.     

The phytoplankton of Lake Atnsjøen, Norway – a long-term investigation

Quantitative samples were collected from Lake Atnsjøen five times per year in the growth seasons 1990–2000. The samples were analysed for variation in the phytoplankton composition, and the total volume and volume of the main groups of algae were calculated. Lake Atnsjøen is a large, deep and unregulated lake with a surface area of 4.8 km² and a maximum depth of 80.2 m. It is a nutrient-poor, oligotrophic lake with a maximum phytoplankton volume varying between 125–393 mm³/m³ in the years 1990–2000. The phytoplankton community is dominated by species of the groups Chrysophyceae and Cryptophyceae. The chrysophytes dominate the phytoplankton in the early part of the growth season (May–June) while the cryptophytes increase throughout the season and dominate in the autumn. Among the chrysophytes different species of chrysomonads were most frequent together with common species of the genus Dinobryon like D. borgei, D. cylindricum var. alpinum and D. crenulatum. A total of 22 species or taxa of chrysophytes were recorded in the samples. Common among the cryptomonads were several species of the genus Cryptomonas. Most important quantitatively, however, were Rhodomonas lacustris and Katablepharis ovalis. The succesion of the phytoplankton throughout the growth season was similar from year to year in quantitative as well as qualitative terms, but some changes were recorded after the great flood in 1995. Canonical Correspondence Analysis (CCA) shows a slight, but significant, phytoplankton community change over the succeeding years.     

External morphology of the male and female of Sphyrion lumpi (Krøyer,1845) (Copepoda; Siphonostomatoida; Sphyriidae)

Sphyrion lumpi is a sexually dimorphic, parasitic copepod which causes significant losses in fisheries in the North Atlantic. Studies involving both light and scanning electron microscopy revealed important details of the external morphology of both sexes that are discussed in relation to other members of the family Sphyriidae. Conclusions are drawn regarding the life cycle of S. lumpi. The present finding of this parasite on Urophycis tenuis constitutes a new host record.     

The association between the caprellid Pariambus typicus Krøyer (Crustacea,Amphipoda) and ophiuroids

The work of Kazutsugu Hirayama over the past 25 yearspromoted the wide use of the marine rotifer Brachionusplicatilis as an experimental model in zooplanktonecology. His reports about the nature of geneticvariation in the B. plicatilis complex stimulated usto investigate how mate recognition maintains speciesboundaries. For the past several years, we haveexamined chemical communication between female andmale B. plicatilis. Here we report on the comparativebinding of polyclonal antibody against the materecognition pheromone (MRP) to three B. plicatilisstrains and three B. rotundiformis strains.Quantification of anti-MRP binding permitsinvestigation of how the female mating signal differsamong closely related Brachionus species and strains.Antibody binding reflects differentiation independentof the male receptor which has been describedelsewhere. Anti-MRP bound to females of all sixstrains and was localized in the corona. Antibodybinding greatly reduced mating in all three B. plicatilis strains. However, antibody bindingsignificantly reduced mating in only one of the B. rotundiformis strains. The MRP of both species has asimilar molecular weight, but the differential bindingsuggests that the mate recognition pheromone onfemales has differentiated in B. plicatilis and B. rotundiformis.     

In search of the Bølling-Oscillation: a new high resolution pollen record from the locus classicus Lake Bølling,Denmark

Vegetation History and Archaeobotany - In a paper from 1942 Johannes Iversen described a warm phase prior to the Allerød warming from lake Bølling in western Denmark and thereby extended...     

A fine-grained sediment budget for the Sylt-Rømø tidal basin

A budget for net accumulation of fine-grained sediment (<63 μm) has been set up for the Sylt-Rømø tidal basin. Net accumulation within the basin was computed from²¹⁰Pb core dating and mapping of the intertidal and supratidal surface sediments. It was found that a yearly mean value of 58·10³ tons of sediment was deposited in the tidal basin. The largest sediment source for the net input of fine-grained sediment is the North Sea contributing about 64% to the net budget; the fluvial input and primary production contribute 14% and 15%, respectively. Local salt marsh erosion accounts for about 5% of the budget and atmospheric deposition for only 2%. The total amount of sediment deposited in the investigated area was low compared with earlier investigations in the Wadden Sea. This is explained partly by the intensive diking of the natural salt marshes fringing the area in the past, and partly by the exposed conditions of most of the intertidal flats. An index describing the trapping efficiency of the water exchanged between the North Sea and the Sylt-Rømø tidal area is defined as the ratio between yearly net sediment input from the North Sea and yearly exchanged water volume between the tidal basin and the sea. This index shows that in the Sylt-Rømø tidal basin, fine-grained suspended sediment “filters” out of the exchanged sea water at a rate that is 12 times lower than in the Gr»dyb tidal basin. It is concluded that the net deposition of fine-grained sediment in a tidal basin is mainly a function of physiographical and hydrodynamical parameters and to a lesser degree of sediment availability     

Molecular Dynamics Simulations of Adrenocorticotropin (1–24) Peptide in a Solvated Dodecylphosphocholine (DPC) Micelle and in a Dimyistoylphosphatidylcholine (DMPC) Bilayer

Abstract

The structure and interactions of the 1–24 fragment of the adrenocorticotropin hormone, ACTH (1–24), with membrane have been studied by molecular dynamics (MD) simulation in an NPT ensembles in two explicit membrane mimics, a dodecylphosphocholine (DPC) micelle and a dimyristoylphosphatidylcholine (DMPC) bilayer. The starting configuration of the peptide/lipid systems had the 1–10 segment of the peptide lying on the surface of the model membrane, the same as the equilibrated structure (by MD) of ACTH (1–10) in a DPC micelle. The simulations showed that the peptide adopts the surface-binding mode and essentially the same structure in both systems. Thus the results of this work lend support to the assumption that micelles are reasonable mimics for biological membranes for the study of peptide binding. The 1–10 segment is slightly tilted from the parallel orientation to the interface and interacts strongly with the membrane surface while the more polar 11–24 segment shows little tendency to interact with the membrane surface, preferring to reside primarily in the aqueous phase. Furthermore, the 1–10 segment of the peptide binds to the DPC micelle in essentially the same way as ACTH (1–10). Thus the MD results are in excellent agreement with the model of interaction of ACTH (1–24) with membrane derived from NMR experiments. The secondary structure and the hydration of the peptide and the interactions of specific residues with the lipid head groups have also been analyzed.     

Ecological requirements of Ostracoda (Crustacea) in a heavily polluted shallow lake,Lake Yeniçağa (Bolu,Turkey)

Although the area of Lake Yeniça?a is a potential candidate for RAMSAR convention, several anthropogenic factors compromise its biological diversity. This is mostly due to nutrient-rich water released from both point and nonpoint sources. Thirteen ostracod taxa (Candona neglecta, C. candida, Ilyocypris bradyi, Darwinula stevensoni, Cypridopsis vidua, Physocypria kraepelini, Cypria ophtalmica, Prionocypris zenkeri, Eucypris virens, Herpetocypris reptans, Pseudocandona compressa, Fabaeformiscandona fabaeformis Potamocypris cf. fulva) were found during this study. Potamocypris cf. fulva is a new record for the Turkish freshwater ostracod fauna. The first nine of these species have broad geographic ranges, implying high tolerance levels to different environmental variables. Based on the estimated species optima and tolerance levels, two species exhibited higher effective number of occurrences (C. neglecta, and D. stevensoni, respectively) than the other species. Three species (C. neglecta, D. stevensoni, I. bradyi) did not show significant correlation with any environmental variable we used. Both Canonical correspondence (CCA) and Pearson correlation analyses showed that temperature was the most effective predictor of species occurrence, followed by electrical conductivity and redox potential. In contrast, pH and dissolved oxygen of water were the least effective predictors. Approximately 71% of the correlation between community composition and environmental variables was explained by the first axis of the CCA diagram, which had a relatively low (7.7%) cumulative variance of species. The lower (560 μg/l) and the upper (2030 μg/l) levels of ammonia (NH₃) exceeded the limits during winter season. The concentrations of total coliform and Escherichia coli bacteria were measured up to 10 × 10⁷ cfu/ml and 10 × 10³ cfu/ml, respectively. Results of physicochemical measurements, microbiological counts, and species data indicate that water quality of Lake Yeniça?a has been rapidly deteriorated by anthropogenic factors that are the main threat for not only the lake’s aquatic diversity but also human health around the lake.