Morphological Response of Microcystis aeruginosa to Grazing by Different Sorts of Zooplankton

In the experiment we investigated the effect of grazing by different sorts of zooplankton on the induction of defensive morphology in the cyanobacterium Microcystis aeruginosa. The results showed that protozoan flagellate Ochromonas sp. grazing could induce colony formation in M. aeruginosa, whereas M. aeruginosa populations in the control and the grazing treatments of copepod Eudiaptomus graciloides, cladoceran Daphnia magna, and rotifer Brachionus calyciflorus were still strongly dominated by unicells and paired cells and no colony forma occurred. In the protozoan grazing treatment, the proportion of unicells reduced from 83.2% to 15.7%, while the proportion of cells in colonial form increased from 0% to 68.7% of the population at the end of the experiment. The occurrence of a majority of colonial M. aeruginosa being in the treatment with flagellates, indicated that flagellate grazing on solitary cells could induce colony formation in M. aeruginosa. The colonies could effectively deter flagellate from further grazing and thus increase the survival of M. aeruginosa. The colony formation in M. aeruginosa may be considered as an inducible defense against flagellate grazing under the conditions that toxin cannot deter flagellate from grazing effectively.     

A Quantitative Comparison of Two Zooplankton Sampling Methods,a Plankton Trap and a Towed Net,in the Baltic

A comparison between a large plankton trap with a capacity of 23 litres and a modern towed net was made in the course of zooplankton production studies in the Baltic. On the average, the net efficiency was 75% of that of the trap. Both methods were equally efficient in catching naupliar stages of copepods. The net efficiency was especially low during the zooplankton maximum for adult copepods and cladocerans (41 and 51%, respectively), probably due to the active avoidance of the net by fast swimming species. The net was only about 66% as efficient as the trap for catching rotifers. This difference is probably caused by the loss of small and softbodied forms through the mesh. Only about 65% of the total zooplankton biomass retained in the trap was collected by the net. Net sampling is not recommended for quantitative zooplankton studies.     

A Comparison of the Zooplankton in Two Newfoundland Bays with Differing Influences from Major Currents

Quantitative zooplankton samples were obtained at four regular stations and one irregular station in Placentia Bay, Newfoundland between mid June 1974 and mid May 1976. Sampling was attempted fortnightly as regularly as weather conditions and competition from other ship users would allow. The results are compared with those obtained and previously published in a similar study from Conception Bay, Newfoundland in 1977 to 1978. There was a greater diversity of species in Placentia Bay, and for most species the numbers/m³ were greater. The two bays are influenced by somewhat different current systems, and climatic conditions are a little milder and foggier in Placentia Bay. The same species were common in both bays, with copepods usually being the most important. Among copepods, two of the most important species namely Pseudocalanus sp. and Oithona similis were less abundant in Placentia Bay, but this was offset by a greater abundance of Temora longicornis. A few of the problems that require further investigation are outlined.     

Calculations of zooplankton grazing rates according to a closed,steady-state,three-compartment model applied to different14C methods

A re-examination of the numerical example of the three-compartment model by CONOVER & FRANCIS (1973) showed that the warning by these authors for the misuse of radio isotopes in transfer studies within food chains is incorrect and based on a misinterpretation of their results. There is no difference in the estimate of transfer rate by use of specific activities or by use of total radioactivities observed in each compartment.After adapting the formulae developed by CONOVER & FRANCIS, their model was used to illustrate deviations of the programmed grazing rate in 3 types of grazing experiments; a) with¹⁴C present only in the phytoplankton at the start of the experiment, b) with¹⁴C only in the water, and c) with¹⁴C in both phytoplankton and water. Up to a duration of the grazing experiment of 2 hours, and at various light conditions and grazing pressures, deviations were small and did not exceed 4%. These results are not directly applicable to practical work because the quantitatively important loss by egestion of radioactive material was not accounted for, only losses by respiration were incorporated in the closed, steady-state model.Best calculations of the community filtering rate (fraction of the volume of the grazing vessel swept clear per day) were generally obtained with the formula (with t in hours) ((DPM zoo at time t)/(DPM phyto at 0+DPM phyto at t)/2)×24/t, applicable to all three types of grazing experiments considered.     

Zooplankton grazing methods using radioactive tracers: Technical problems

Some of the technical problems specific to the application of radiotracer techniques for measuring grazing of zooplankton are highlighted and, in some cases, the corrective measures suggested.The major drawbacks of measuring zooplankton grazing in the laboratory, for studying the role of zooplankton in nature, namely, changes in water temperature and light and heavy mortality of some cladocerans, are overcome by the use ofin situ grazing chambers. However, at present there are no suitable techniques available to measure short-term assimilation rates which usually suffer from the respiratory loss during the experiment of the assimilated radiotracer.In the ecosystem research in which zooplankton grazing is an integral part of the studies, the radiotracer food manufactured fromin situ lake seston is preferred to labelled monoculture of algae, bacteria or yeast. The specific activities of the different tracer components and size fractions of the seston comprising the tracer may considerably differ in short-term labelling. On the other hand, long labelling periods,i.e. exceeding a day for example, may lead to shifts in size spectra of and composition of the different phytoplankton species. Changes during the incubation in the size spectra of the tracerfood are probably of greater importance than those in species composition, especially because a size-selective feeding may often exist.Simultaneous use of different radiotracers for labelling phytoplankton and bacteria or for mixtures of algae that differ in sizes offers some promising applications. More work in this field is needed, particularly because of the overlapping energy spectra of the radiotracers, and differential loss rates of these tracers from the preserved animals before the radioactivity counting. Such losses of the tracer from the experimental animals may lead to significant errors, especially in the short-term grazing measurements. This problem can be, nevertheless, prevented to a large extent by a rapid freeze-drying of the animals immediately on concluding the experiment.Self absorption may be a problem in radioactivity counting, more so if the animals are large. Use of sample oxidizers offers a good solution if the tracer can be trapped in its oxidized, gaseous form (e.g. ¹⁴CO₂) before further processing for counting. Modern solubilizing agents, like Soluene 350, with their relatively high water-holding capacity are quite effective in dissolving the different tissues, except the exoskeletal material.dedicated to Prof. H.F. Linskens, chairman of the Managing Committee of the Limnological Institute, in honour of his 65th birthday.     

Active Bacterial Populations and Grazing Impact Revealed by an In Situ Experiment in a Shallow Aquifer

To elucidate bacterial population dynamics in an aquifer, we attempted to reveal the impact of protozoan grazing on bacterial productivity and community structure by an in situ incubation experiment using a diffusion chamber. The abundance and vertical distribution of bacteria and protozoa in the aquifer were revealed using wells that were drilled in a sedimentary rock system in Itako, Ibaraki, Japan. The water column in the wells possessed aerobic and anaerobic layers. Active bacterial populations under the grazing pressure of protozoa were revealed through in situ incubation with grazer eliminating experiment by the filtration. On August 19, 2003, the total number of bacteria (TDC) decreased from 1.5 × 10⁶ cells ml^{? 1} at 2.2 m depth to 3.0 × 10⁵ cells ml^{? 1} at 10 m depth. The relative contribution of the domain Bacteria to TDC ranged between 63% and 84%. Protozoa existed at a density of 4.2 × 10⁴ to 1.9 × 10⁵ cells ml^{? 1} in both aerobic and microaerobic conditions. A grazing elimination experiment in situ for 6 days brought about clearly different bacterial community profiles between the 2.2 m and 10 m samples. The bacterial composition of the initial community was predominantly β- and γ -proteobacteria at 2.2 m, while at 10 m β-, α - and γ -proteobacteria represented 56%, 26% and 13% of the community, respectively. The distribution of bacterial abundance, community composition and growth rates in the subsurface were influenced by grazing as well as by geochemical factors (dissolved oxygen and concentrations of organic carbon, methane and sulfate). Results of the in situ incubation experiment suggested that protozoan grazing contributes significantly to bacterial population dynamics.     

高寒草甸放牧扰动与两种植物的反应研究

对不同放牧强度下矮嵩草草甸植物垂穗披碱草和鹅绒委陵菜的生长和繁殖特性进行了5年研究。结果表明,垂穗披碱草株高、分蘖数、地上物量、地下生物量、有性繁殖效力在不放牧或轻度放牧下最大,营养生长效力在重度放牧中最大,而贮藏效力在重度放牧中最小。鹅绒委陵菜叶数、匍匐茎长度、地上生物量、匍匐茎生物量、开花数、生殖生物量、有性繁殖效力及营养繁殖效力在放牧区显著高于不放牧的对照区。说明适当的放牧干扰有利于垂穗披碱草营养生长,但放牧过重会抑制其有性繁殖;由于放牧采食减少了种间竞争影响,从而提高了鹅绒委陵菜营养,生长效力和有性繁殖效力。两物种地下贮藏物的比例随着放牧强度增加显著减少。放牧强度对高寒草甸的群落演替方向有显著影响。     

Different Predation Impacts of Two Cyclopoid Species on a Small-sized Zooplankton Community: An Experimental Analysis with Mesocosms

We used mesocosms to analyze predation impacts on the prey populations and prey community structures by two cyclopoid copepod species, the larger Mesocyclops pehpeiensis and the smaller Thermocyclops taihokuensis, who coexist with small-sized herbivorous zooplankton species in a fish-abundant lake. The overall predation impact on the prey populations was stronger for Mesocyclops than for Thermocyclops. Mesocyclops had a strong and less selective impact on the rotifer community but a selective impact on the crustaceans. In contrast, Thermocyclops had a selective predation impact on rotifers but a weak and less selective impact on the crustacean community. As a result, the former predator reduced the diversity of the crustacean community but not the rotifer community, while the latter had an opposite impact on the diversities of the two communities. It has been suggested that fish induce development of a zooplankton community dominated by the small-sized zooplankton species in fish-abundant lakes. Our results demonstrated that cyclopoid copepods altered species composition and diversity of the small-sized zooplankton community in such lakes. Thus, the results have given an important suggestion on the role of the invertebrate predator cyclopoid copepods, which often coexist with fish, that they determine population dynamics and community structures of small-sized zooplankton in fish-abundant lakes.     

Seasonal Variation in the Biomass of Zooplankton in Two Shallow Coastal Water Inlets Differing in their Stage of Eutrophication

The seasonal zooplankton dynamics of two coastal water inlets differing in their stage of eutrophication are compared. There are no clear differences between the two waters with respect to calanoid copepods, but they differ appreciably in terms of rotifer biomass. In the more eutrophic water the latter show a pronounced mass development in July which is absent in the less eutrophic water. It is concluded that bacterio-detritivorous rotifer species are an important regulative factor of the ecosystem which compensates for productivity increases by intensifying heterotrophic destruction.     

煮沸裂解法和试剂盒法提取浸矿菌基因组DNA的比较

目的:在生物浸出中,微生物群落结构分析有着重要意义,而群落分析的基础是提取纯度高、损失少的基因组DNA。为了解决这一问题,本实验通过比较两种较常用的DNA提取方法,煮沸裂解法和试剂盒法,寻找一种灵敏、快速、经济实用的制备浸矿细菌基因组DNA的方法。方法:分别用煮沸裂解法和试剂盒法提取6种浸矿菌的基因组DNA,从所提取的基因组DNA浓度、纯度、回收率和对PCR扩增反应的影响方面比较了两种方法的提取效果;用两种方法来处理不同浓度梯度的一种菌,通过实时定量PCR来比较两种方法的灵敏性。结果:相同处理量(108个)的革兰氏阳性菌(1株)、革兰氏阴性菌(4株)、古菌(1株)经两种方法提取的基因组DNA差异较大,煮沸裂解法所得的6组基因组DNA更纯,其OD260/OD280的值更接近1.8-2.0(纯DNA的OD260/OD280在1.8-2.0之间),前者所提DNA回收率最大可达后者的16.7倍;煮沸裂解法只需较少菌(102个)便能让实时定量PCR检测到所提DNA模板浓度,比试剂盒法灵敏。结论:两种方法提取的基因组DNA均可用于后续的PCR扩增,此外,前者提取的DNA浓度随细菌浓度增加而呈线性增大,而后者随菌浓度增大,所提DNA量增加有限,因此,在生物浸出中微生物基因组DNA的提取可直接采用简单快速的煮沸提取法,为实验节约成本和时间。     

赤拟谷盗模拟种公畜选择──常规与改进方法的比较

本实验用实验昆虫赤拟谷盗两个世代各３０个家系的８５９和７２６只蛹的２３日龄蛹长和蛹宽作为选择性状模拟种公畜选择,对常规方法和改进方法进行比较。以Ｈｅｎｄｅｒｓｏｎ方法Ⅲ和综合指数作为常规方法,用约束最大似然法（ＲＥＭＬ）和ＢＬＵＰ估计方差组分和育种值为改进方法。结果表明,常规法估计遗传参数在两世代中不稳定,而改进方法弥补此缺点。对两世代个体和家系育种值排队,结果表明两种方法在前几名无差别,说明在选择强度大（留种率低）时,两种方法效果基本一致。     

Statistical Validation of Two Sample Comparison Methods for Oligonucleotide Microarray in Rat Ischemia Model

In gene expression analyses using a high-density oligonucleotide array in a rat ischemia model, two comparison methods, “pair-wise comparison” and “sample average comparison”, were evaluated based on statistical methods. The reliability of the elements screened with a 1.2 to 10-fold threshold was also evaluated. In pair-wise comparisons, most of the elements were significantly independent of the threshold value, with the percentage of significant elements remaining above 95%, when screened at 2.5-fold or higher threshold value. Pair-wise comparison structurally provided strict screening, which resulted in genes that were not selected despite significant alterations in expression. Screening by “sample average comparison” resulted in elements with low probability of significance, which suggested the necessity for increasing the reliability by additional statistical analyses after screening. When genes with altered expression were screened using an oligonucleotide array, marked differences in the numbers and reliability were proved to exist among elements screened by each sample comparison method.     

两种测试方法对DPPH分光光度法测试结果的影响

目的:比较固定反应时间法和动力学监测法的准确性。方法:用固定反应时间法和动力学监测法分别测定维生素C(Vc)、二丁基羟基甲苯(BHT)对二苯代苦味酰自由基(DPPH)的清除作用,通过F检验和t检验来揭示两种方法的差异。结果:通过动力学监测法得到的测试结果更能准确的反映测试样品对DPPH自由基的清除能力。结论:建议在用DPPH分光光度法过程中使用动力学监测法。     

Zooplankton biomass rarely improves predictions of chlorophyll concentration in Canadian Shield lakes that vary in pH

To determine the frequency with which zooplankton influence chlorophyll a (Chla) levels, we explored annually-averaged data from oligotrophic and mesotrophic lakes that differed in morphometry, total phosphorus (TP) concentrations, and zooplankton community composition due to pH. The data were divided into two sets according to the type of filter used to collect chlorophyll. Residuals of the Chla: TP regressions were not related to lake morphometry, TN content, water clarity or pH. In the first data set there were no consistent relationships between residuals in Chla and twelve grazer biomass variables for 37 of the 38 lakes. The single exception had a very large population of Daphnia dubiaand low concentrations of Chla for its TP. In the second data set, 3 of 25 lakes had exceptionally low Chla concentrations for their TP. These lakes were acidic (pH < 6) and had very large biomasses of Holopedium gibberumcorrelated with negative Chla residuals, indicating significant grazing. At pH > 6, Daphnia spp. strongly influenced the significant correlations. We conclude that zooplankton contribute to the prediction of Chla beyond that possible by TP alone in acidic and non-acidic Canadian Shield Lakes, but evidence for strong suppression of chlorophyll by grazers was relatively rare (4 of 63 cases) on annual time steps.     

Application of Numerical Classification to Study the Grazing Retrogressive Succession Stages of the Kobresia Vegetation on the Subalpine Meadow

Using the nearest-neighbour method in the course of numerical classification the four stages of the grazing retrogressive succession .of the Kobresia vegetation in Maqu Xian are divided: Ligularia virgaurea +Stipa aliena -Saussurea sp community and Leontopodium sp-Saussurea superba f. Pygmaea community belongs to the RSS (Retrogressive Succession Stages) of the grazing extremely; Anemone rivularis var fioreminore-Ligularia virgaurea-Kobresia spp community belongs to the RSS of the grazing seriously; Brachy-podium sylvaticum var gracile-Kobresia spp, Kobresia spp-Polygonum viviparum-Festuca rubra and Kobresia spp-Blysmus sinocompressus -Potentilla anserina communities belong to the RSS of the grazing moderately; Kobresia spp-Trollius farrei community belongs to the RSS of the grazing properly. Such classification method gives the same result as the traditional classificational methods of the RSS do. But it gives the numerical bases.     

两种少量小鼠外周血间期核FISH技术的比较

目的:探讨低渗法与红细胞裂解法应用于小鼠少量外周血间期核荧光原位杂交(fluorescence in situ hybridization,FISH)检测的优缺点,以便于根据实验条件选取最合适的方法。方法:小鼠剪尾巴法获取外周血,采用低渗法或红细胞裂解法破坏红细胞,涂片前先用免疫组化笔在玻片上划好预计涂片区域,重悬沉淀后稍等片刻再吸中间部分用于涂片,涂完后在相差显微镜下观察密度,行常规FISH,比较两种方法处理后的FISH结果。结果:低渗法和红细胞裂解法处理后的片子背景都较干净,密度适中,信号较强。结论:在外周血间期核荧光原位杂交技术中,低渗法和红细胞裂解法都可以获得较满意的FISH结果。低渗法的特点在于试剂便宜且易于获取,但耗时稍长;而红细胞裂解法的特点在于可节省实验时间,但需专用试剂。     

Influence of Temperature,Photoperiod and Trophic Conditions on the Seasonal Cycles of Phytoplankton and Zooplankton in Two Deep Subarctic Lakes of Northern Canada

The densities of phytoplankton and zooplankton were determined for 12 consecutive months (1978–1979) in two deep oligotrophic lakes in northern Canada. The lakes were situated on the same river system, about 5 km from one another. While they exhibited similar temperature conditions, there were slight differences in the ionic content of the water. Overall, changing temperature was the most important factor influencing the duration of the growth cycles of phytoplankton and zooplankton. Nutrients generally controlled the intensity but not the timing of algal blooms. A similar relationship was recorded for the effects of food supply on the development of the major species of herbivorous zooplankton. Although changing photoperiod likely initiated the growth of several important algal and zooplankton species in the spring and early summer, light had no measurable impact on the development of planktonic communities throughout the remainder of the growing season. The higher ionic content of the water in one lake may have promoted the growth of protozoans during the fall and early winter.     

两种分离斑马鱼卵母细胞方法的比较

对培养斑马鱼卵母细胞体外成熟中的两种分离方法进行了比较。结果表明,在卵母细胞的分离过程中,机械分离法获得的完整卵细胞的比例(87.0%)显著多于EDTA-胰酶消化法(33.2%)(P<0.01)。但机械分离法较费时,其平均分离每个卵细胞所用的时间(0.69min)显著多于EDTA-胰酶消化法(0.17min)(P<0.01)。此外,经过18h 27℃培养,机械分离法获得的卵细胞的存活率(88.2%)显著高于EDTA-胰酶消化法所获卵细胞的存活率(60.1%),而采用机械分离法和消化分离法对所获卵细胞的成熟度-GVBD%分别为83.9%、77.5%,无显著差异(P>0.05)。基于数据所示,机械分离法可以获得存活率高、完整性好的卵细胞,但所需操作时间较长;EDTA-胰酶消化法操作便捷,但其分离出的卵细胞的活力较差;两种方法对卵细胞体外培养成熟率的影响无明显差异。     

Local Adaptation and Effects of Grazing among Seedlings of Two Native California Bunchgrass Species: Implications for Restoration

Adaptation to environmental factors may influence the germination and establishment of focal species in ecological restoration. Reciprocal transplants remain one of the best methods to detect local adaptation, but long‐term studies are often not feasible. We conducted reciprocal transplants of the native California bunchgrasses Elymus glaucus and Bromus carinatus between two central California locations to seek evidence of adaptation to local environmental conditions in a single growing season. Experimental plots at one location included grazed and ungrazed sites. The combination of locations and grazing treatments allowed us to determine whether the ability to detect evidence for adaptation depended on grazing regime. In addition, we measured the direct effects of grazing on seedling growth and survival concurrent with our investigation of local adaptation. We detected a homesite advantage for seedling growth or survival in both species, but the factors contributing to adaptive differentiation were species specific. Evidence of local adaptation was detected for seedling biomass in Bromus and for survivorship in Elymus. The homesite advantage observed in both species was greatly reduced under grazed conditions and in Elymus was significant only in the ungrazed plots. Climate and soil analyses detected significant differences between locations in five soil attributes and two climate variables. In particular, differences in exchangeable magnesium indicated that one of the two transplant locations consisted of serpentine soil, which is widely known to drive adaptation in plant populations. Together, these results suggest that it is possible to investigate the scale and factors involved in local adaptation with short‐term transplant studies.     

两种教学方法在护理专业人体形态学教学中的应用及比较

目的:探讨A和B两神教学方法在护理专业人体形态学教学中的应用及比较.方法:通过应用A和B两种教学法,对全日制护理学专科2010-2班和护理学专科2011-2班的人体形态学期末考试平均成绩和及格率进行比较和分析.结果:采用A教学法的护理学专科2011-2班的最高分为88分,最低分为42,平均成绩为75.45分,标准差为10.34.采用B教学法的护理学专科2010-2班的最高分为84分,最低分为36,平均成绩为64.34分,标准差为11.65.对护理学专科2011-2班和2010-2班的平均成绩进行F检验,F=1.12＜1.50,故P＞0.10,方差齐,敌可用方差相等情形的两样本t检验,t=5.36＞2.66,故P＜0.01,两组平均成绩之间差异有统计学意义;采用A教学法的护理学专科2011-2班的及格率为81.54％,采用B教学法的护理学专科2010-2班的及格率为65.15％.对于以上两个班及格率进行卡方检验,x=4.49＞3.84,故P＜0.05,两组及格率之间差异有统计学意义.以上结果说明采用A教学法的护理学专科2011-2班的平均成绩和及格率明显高于采用B教学法的护理学专科2010-2班.结论:在人体形态学教学中,A教学法跟B教学法比具有明显的优势,同时A教学法自身也有不足之处.