食物浓度对角突臂尾轮虫种群增长、个体大小和卵大小的影响

以蛋白核小球藻为食物 ,应用群体累积培养法研究了食物浓度对角突臂尾轮虫种群增长、个体大小和卵大小等的影响 .结果表明 ,食物浓度对角突臂尾轮虫种群增长率、个体大小和卵大小均有极显著影响 .其中 ,轮虫种群增长率与食物浓度间呈曲线相关 ;当食物浓度为 8.2 4 5 3× 10 6cells·ml-1时 ,种群增长率达最大值 0 .6 0 85d-1;在所研究的食物浓度范围内 ,轮虫个体具有随食物浓度的增大而增大的趋势 ,轮虫卵体积在中等食物浓度范围 (6 .0× 10 6～ 9.0× 10 6cells·ml-1)时较大     

三氯杀螨醇浓度和食物密度对萼花臂尾轮虫种群增长的影响

采用群体累积培养方法,研究了不同浓度(0.03、0.3、3.30和300 μg·L-1)的三氯杀螨醇和不同食物密度(3.0和5.0×106cells·ml-1)的斜生栅藻(Scenedesmus obliquus)对萼花臂尾轮虫(Brachionus calyciflorus)种群增长影响.结果表明:藻类食物密度、三氯杀螨醇浓度以及二者的交互作用对轮虫种群增长率均有显著影响(P＜0.05);藻类食物密度和三氯杀螨醇浓度对轮虫最大种群密度也有显著影响(P＜0.01),但二者的交互作用对其却无显著作用(P＞0.05);与空白对照组相比,在3.0×106cells·ml-1藻密度下.0.03-30μg·L-1的三氯杀螨醇显著提高了轮虫种群增长率,3μg·L-1的三氯杀螨醇显著降低了轮虫的最大种群密度,而300μg·L-1的三氯杀螨醇则极显著提高了轮虫的最大种群密度;在5.0×106cells·ml-1藻密度下,三氯杀螨醇对萼花臂尾轮虫种群增长率和最大种群密度均无显著影响;高密度的藻类食物降低了0.03-30μg·L-1和300μg·L-1的三氯杀螨醇分别对萼花臂尾轮虫种群增长率和最大种群密度所具有的促进作用,以及3μg·L-1的三氯杀螨醇对轮虫最大种群密度所具有的抑制作用.     

温度对三品系角突臂尾轮虫生活史策略的影响

应用群体累积培养法 ,以浓度为 6 .0× 10 6cells/mL蛋白核小球藻 (Chlorellapyrenoidosa)为食物 ,研究了温度(2 0℃、2 5℃和 30℃ )对青岛、广州与芜湖等品系的角突臂尾轮虫 (BrachionusangularisGosse)的种群增长、个体大小和卵大小的影响。结果表明 ,温度对各品系轮虫的种群增长率和个体大小等均有显著影响。青岛品系和广州品系轮虫种群增长的最适温度分别为 30℃和 2 5℃ ,芜湖品系轮虫则在 30℃下不能生存。青岛品系和广州品系的种群增长率均与温度呈曲线相关 ,回归方程分别为 :Y =0 .0 0 0 9X2 - 0 .0 0 6 1X 0 .4 0 90和Y =- 0 .0 14 4X2 0 .74 12X - 8.375 1。各品系轮虫个体大小和卵大小均随温度的升高而呈现出下降趋势。在本研究的温度范围内 ,广州、青岛和芜湖各品系轮虫个体变异分别达 4 2 .90 %、14 .4 3%和 6 .2 3% ;2 0℃和 2 5℃下芜湖品系分别高出青岛品系达 74 .91%和87.98%。在温度和品系两因素中 ,品系对轮虫个体体积有较大的影响     

种群起始密度对萼花臂尾轮虫休眠卵形成的影响

应用群体累积培养法,研究了种群起始密度对萼花臂尾轮虫休眠卵的形成及之相关的混交雌体百分率和受精率的影响,结果表明,在连续１１ｄ的培养中,轮虫休眠卵的产量和形成效率以及种群中的平均混交雌体百分率以种群起始密度为１．０－１０．０ｉｎｄ．ｍｌ＾－１组最大,２０．０ｉｎｄ．ｍｌ＾－１组次之,５０．０ｉｎｄ．ｍｌ＾－１组最小,各组间的平均混交雌体受精率则无显著差异,对轮虫休卢卵最大形成效率及其出现的时间以及     

食物浓度对三个地理品系角突臂尾轮虫种群增长、个体大小和卵体积的影响

以浓度分别为 3 0× 10 6、 6 0× 10 6、 9 0× 10 6和 12 0× 10 6cells/mL蛋白核小球藻 (Chlorellapyrenoi dosa)为食物 ,在温度为 (2 5± 1)℃下 ,应用群体累积培养法研究了食物浓度对分布于长江、珠江和淮河水系的 3个地理品系的角突臂尾轮虫 (Brachionusangularis)种群的增长、个体和卵的体积的影响。结果表明 ,食物浓度、地理品系及两者间的交互作用对轮虫种群增长率、个体和卵的体积均有显著影响。同一食物浓度下 ,广州品系的种群增长率最大 ,芜湖品系的个体和卵体积最大 ;同一品系中 ,当食物浓度为 9 0× 10 6cells/mL时轮虫有较大的种群增长率。各品系轮虫的种群增长率与食物浓度均呈曲线相关 ,但种群增长率达最大时所需的食物浓度在各品系间存在着差异。在食物浓度和品系两因素中 ,品系对轮虫个体体积有较大的影响     

新安江水域(屯溪段)轮虫的种群增长研究

应用群体培养法对采自新安江水域(屯溪段)的萼花臂尾轮虫在4种不同温度(15℃、20℃、25℃和30℃)下的种群动态进行研究。结果表明,温度对轮虫的种群增长率和休眠卵产量均有显著影响(P<0.05)。随着培养温度的升高,轮虫的种群增长率逐渐增大;休眠卵产量在15℃时最小,其余温度下无显著差异。轮虫的总雌体密度在25℃最大,15℃最小;4温度下,雄体和产雄卵的混交雌体的生产量15℃下最小,25℃下最大;而产休眠卵的混交雌体的生产量在15℃下最小,20℃下最大。温度对轮虫的平均混交雌体百分率和平均混交雌体受精率均无显著影响。     

斜生栅藻密度对新安江萼花臂尾轮虫种群动态的影响

以浓度分别为1.0×106、2.0×106、4.0×106和8.0×106cells·mL-1的斜生栅藻(Scenedesmus obliquus)为轮虫食物,在25℃下,应用群体累积培养和单个体培养法研究了食物浓度对采自新安江水域(屯溪段)的萼花臂尾轮虫的种群动态影响。结果表明:食物浓度对轮虫的种群增长率和休眠卵产量均有显著的影响,均表现为低食物浓度下(≤4.0×106cells·mL-1)萼花臂尾轮虫的种群增长率和休眠卵产量较小且无差异,高食物浓度下(8.0×106cells·mL-1)轮虫的种群增长率和休眠卵产量较大;食物浓度对轮虫的混交雌体百分率和受精率无显著影响;在食物浓度为4.0×106cells·mL-1时萼花臂尾轮虫的净生殖率最大,世代时间最长,而其内禀增长率在食物浓度为1.0×106cells·mL-1时最小;在食物浓度为8.0×106cells·mL-1时平均寿命和生命期望最长。     

几种培养方法对萼花臂尾轮虫(Brachionus calyciflorus)种群密度及其环境因子影响的比较研究

分别利用泥鳅 -藻 -轮虫和罗非鱼 -藻 -轮虫共生隔离培养的方法 ,研究萼花臂尾轮虫 ( Brachionuscalyciflorus)的种群密度和主要环境因子的变化。研究结果表明 :加入泥鳅的培养缸中 ,有 1 1 d轮虫数量超过 1 0 0 ind/ml,其中有 5d超过 2 0 0ind/ml,最高密度达 2 50 ind/ml;在罗非鱼的培养缸中 ,在整个实验过程中 ,种群密度超过 1 0 0 ind/ml以上的时间有 6d(第5～ 1 0天 ) ;单纯利用藻类培养轮虫时 ,种群密度较低 ,且维持时间较短 ,最高种群密度不足 1 0 0 ind/ml,利用藻类 -轮虫 -鱼类共存同一生态系统中 ,并使鱼类和轮虫隔离进行生态培养时 ,能提高轮虫种群密度 ,延长种群高峰期     

两种饵料对褶皱臂尾轮虫生殖及休眠卵孵化的影响

四列藻被认为是介导广盐性轮虫有性生殖的优质饵料。然而,新鲜的四列藻培养成本高且营养单一难以维持轮虫的高密度、高质量培养。因此,寻找一种营养素含量高、经济效益好,且能提高轮虫增殖效率的商业化饵料对水产养殖业的发展有重要意义。本研究通过比较四列藻和富硒小球藻对褶皱臂尾轮虫复合品系(日本品系和澳大利亚品系)的生殖及休眠卵孵化率的影响,探究了富硒小球藻饵料在轮虫高密度培养中的可用性。研究发现,日本品系轮虫,富硒小球藻组的休眠卵孵化率(70.0±11.1)%显著高于四列藻组(24.0±10.8)%(p0.05);而澳大利亚品系,虽然休眠卵孵化率在两种饵料间无显著性差异,但小球藻组的种群生长率(0.28±0.02)高于四列藻组(0.23±0.00)(p0.05)。由此可见,富硒小球藻有利于褶皱臂尾轮虫复合品系的种群增长和有性繁殖。此外,富硒小球藻饵料组轮虫的体长和体宽均小于四列藻组,这一结果也证明了轮虫种群密度越大,体型越小的理论。本研究结果显示在褶皱臂尾轮虫复合品系的高密度培养中,商业化的富硒小球藻有望替代四列藻成为一种有效的提高轮虫有性生殖效率的饵料。     

食物种类和浓度对红臂尾轮虫种群增长、个体大小及卵大小的影响

采用群体累积培养法,研究了藻类食物的种类和浓度对红臂尾轮虫种群增长、个体大小及卵大小的影响．结果表明,藻种类和浓度对红臂尾轮虫种群增长率、个体体积及卵体积均有极显著影响．不同食堕种空中,种群增长率以小球藻组最小,栅藻组最大;个体体积以小球藻组最小,栅藻组和混合藻组问无显著差异．种群增长率(Y,d^-1)与食物浓度(X,×10^6cells·ml^-1)间呈曲线相关,两者间的关系符合方程：y＝-0．0040x^2+0．0409X+0．4471。在所研究的食物浓度范围内,当浓度分别高于或低于6．0×10^cells·m1^-1和3．0×10^6cells·ml^-1时,轮虫个体体积和卵体积均分别呈减小的趋势。     

Effect of Food Quantity and Quality on Population Growth Rate and Digestive Activity in the Euryhaline Rotifer Brachionus plicatilis Müller

We investigated the nutritional effects of both food quantity and quality on Brachionus plicatilis. Decomposition of particulate and dissolved organic matter by rotifer digestive enzymes play a crucial role in rotifer nutrition. Among other enzymes, rotifers produce phosphatases, non‐specific enzymes that allow for the release of orthophosphate from a variety of organic phosphorus compounds. Phosphatase saturation was measured in B. plicatilis homogenates using the spectrofluorimetric method. We examined population growth rate, reproduction and phosphatase activity in the homogenate of rotifers (PA_RH) fed by nutrient‐replete algal food supplied at different quantities. Population growth rate, number of eggs per individual and PA_RH were affected by food quantity. Growth rate and number of eggs per individual significantly increased in rotifers fed by food supplied at the highest quantity. The highest population growth rate was reached by rotifers fed by nutrient‐replete food, while it did not significantly differ between rotifers fed on nitrogen (N)‐depleted and phosphorus (P)‐depleted food. The number of eggs per individual was more affected by N than P supply. PA_RH and rotifer RNA content were not influenced by different food quality. The results indicate that B. plicatilis is not able to regulate its digestive apparatus in terms of efficiently getting access to essential nutrients when scarce, but do this when nutrient‐replete food is available in different quantity. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Use of swimming speed and egg ratio as predictors of the status of rotifer cultures in aquaculture

This study evaluated the use of egg ratio (eggs rotifer^–1) and swimming speed (mm min^–1) as prediction criteria for production and culture quality in mass cultures of the rotifer Brachionus plicatilis. Egg ratio was determined to be a suitable predictor of rotifer growth and production in the cultures. Low egg ratios (i.e., 0–0.17 eggs rotifer^–1) indicate reduced rotifer population over time (i.e., negative net population growth rates). However, at this time egg ratio dynamics are not suitably understood to predict in advance a sudden population collapse.Swimming speed of reproductive, egg-carrying females in the exponential growth phase was 40–45 mm min^–1. During exponential growth swimming speed was independent of the food used. Lower swimming speeds were obtained in late stationary phase (10–25 mm min^–1) when yeast was used as a food source. Both environmental factors (e.g., accumulating metabolites) and changes in nutritional state of the rotifers may have affected the swimming speed, but environmental factors appear to be the most important. We believe that swimming speed has the potential of becoming an accurate predictor of culture quality in mass cultures of rotifers.     

Estimating population birth rates of zooplankton when rates of egg deposition and hatching are periodic

Summary I present a general method of computing finite birth and death rates of natural zooplankton populations from changes in the age distribution of eggs and changes in population size. The method is applicable to cases in which eggs hatch periodically owing to variable rates of oviposition. When morphological criteria are used to determine the age distribution of eggs at the beginning and end of a sampling interval, egg mortality can be incorporated in estimates of population birth rate. I raised laboratory populations of Asplanchna priodonta, a common planktonic rotifer, in semicontinuous culture to evaluate my method of computing finite birth rate. The Asplanchna population became synchronized to a daily addition of food but grew by the same amount each day once steady state was achieved. The steady-state rate of growth, which can be computed from the volume-specific dilution rate of the culture, was consistent with the finite birth rate predicted from the population's egg ratio and egg age distribution.     

鄱阳湖采砂南移扩大影响范围——多源遥感的证据

采砂是一项具有巨大生态影响的经济活动.利用多源遥感影像描述鄱阳湖中部的采砂分布,分析其对悬浮泥沙浓度的影响.2011年7月28日的Landsat Thematic Mapper (TM)5用于采砂相关船只的识别,2009-2011年7-8月的Terra卫星中分辨率成像光谱仪(MODIS)影像用于悬浮泥沙浓度的反演,(Before-after-control-impact,BACI)方法用于采砂影响评价.Landsat TM 5影像解译结果发现鄱阳湖中部的两个采砂区和90余艘船只,MODIS Terra反演结果显示在采砂区及其下游区域悬浮泥沙浓度剧增,BACI评价结果揭示采砂是导致此区域悬浮泥沙浓度增加的主要因素.平衡经济发展与生态保护之间的关系,将因采砂而造成的负面影响降到最低,使鄱阳湖的各种生态功能全面发挥是紧要的.     

Effects of silt loading on the feeding and mortality of the mysid Mesopodopsis africana in the St. Lucia Estuary, South Africa

Mesopodopsis africana is an abundant zooplankton species in the currently drought stricken St. Lucia Estuary. The estuary is freshwater-starved, partly because its connection with the large Mfolozi catchment has been discontinued. This is due to the extremely high silt load carried by its waters. A series of in vitro experiments were conducted in May, July, August and December 2006, in order to determine the effect of silt loading on the feeding rate and mortality of M. africana. Mysids were subjected to different sediment concentrations in controlled experiments for a 12-hour period. The turbidity regimes were generated by adding pre-weighed silt concentrations, ranging from 0.03 g/L to 13 g/L, to natural estuarine water. Results in all cases showed a major effect of high silt levels upon food availability, as water chlorophyll losses increased with increased silt concentration. Hindrance in the food collecting abilities appears to have a compounding influence as on two occasions, May and August, ingestion rates decreased with an increase in silt concentration. However, in July, mysid ingestion and clearance rates were higher under increased suspended silt concentrations. In such cases, mysids may be clearing more water under conditions of low food concentration, or alternatively, they may switch to feeding on metazoan prey. In the December experiment, there was no relationship between ingestion rate and silt concentration, possibly because food supplies were sufficient to sustain constant ingestion rates or because mysids increased their clearance rates in the more turbid treatments to compensate for any negative effects of silt. Mysid health also declined, with the mean percentage of survivors decreasing consistently with an increase in silt concentration. Results indicate that the overall effect of increased silt load is negative, and subsequently, increased silt loading in the St. Lucia estuary is expected to have detrimental effects on communities of mysids within the estuary.     

A model evaluating the contribution of environmental factors to the production of resting eggs in the rotifer Brachionus plicatilis

The production of resting eggs by the rotifer Brachionus plicatilis was tested at four salinities (9, 18, 27 and 36\%) and six concentrations of the alga Chlorella stigmatophora (0.25, 0.5, 1.0, 2.0, 4.0 and 6.0 × 10⁶ cells ml^–1). The results indicated that resting eggs were produced only at two salinities (9\% and 18\%) and that their number was affected by the amount of food provided. A model consisting of two generalized linear sub-models was built to evaluate the contribution of each of the tested food concentrations at the two salinities. The sub-models were used to distinguish between two different components of resting egg production: one related to the presence or absence of resting egg production, and the other to the number of resting eggs produced, given that production had occurred. Besides indicating the best combination of salinity and food concentration for obtaining large numbers of resting eggs, they revealed the contribution of internal population factors that were not controlled in the course of the experiment. The model identified the positive contribution of the relative number of females to males, and the negative association between high rotifer densities and the production of resting eggs. The results of the present study help in defining the optimal conditions for mass production of resting eggs, which are of potential importance in aquaculture.Deceased, September 1991.