红臂尾轮虫和壶状臂尾轮虫生活史特征比较

应用单个体培养方法,以浓度为3．0×10^6 cells／ml的斜生栅藻（Scenedesmus obliquus）为食物,在18、23、28℃和33℃下,对分类存疑种类红臂尾轮虫（Brachionus rubens）和壶状臂尾轮虫（B．urceolaris）的生活史特征进行了比较研究。结果表明,随着温度的升高,两种轮虫的生殖前期和生殖期历时、平均寿命、世代时间和生命期望均逐渐显著地缩短,而种群内禀增长率却极显著地增大。红臂尾轮虫在28℃下的生殖后期历时与23℃和33℃间均无显著的差异,壶状臂尾轮虫在28℃和33℃下的生殖后期历时也无显著的差异。红臂尾轮虫的产卵量和净生殖率均在33℃下最小,在其他3个温度间都无显著的差异;壶状臂尾轮虫的产卵量和净生殖率均在33℃下最小,28℃下最大。18、23℃和28℃下红臂尾轮虫的生殖前期历时、平均寿命、生命期望和世代时间都显著短于壶状臂尾轮虫,而生殖期历时在两者间无显著差异;33℃下红臂尾轮虫的生殖期历时、平均寿命、生命期望和世代时间都显著长于壶状臂尾轮虫,而生殖前期历时在两者间无显著差异。各温度下,红臂尾轮虫的产卵量、种群内禀增长率和净生殖率均极显著地高于壶状臂尾轮虫,但两种轮虫的生殖后期历时无显著的差异。红臂尾轮虫偏向于r-对策者,体现在其较低的生命期望、较高的繁殖率和种群增长率;而壶状臂尾轮虫则显示出较高的生命期望、较低的种群增长率和繁殖率,偏向于k-对策者。     

pH值对萼花臂尾轮虫种群增长及繁殖的影响

采用种群积累培养法,实验观察了 ｐＨ在３．５～１１．５之间（间隔 １）萼花臂尾轮虫 （Ｂｒａｃｈｉｏｎｕｓ ｃａｌｙｃｉｆｌｏｒｕｓ）种群的增长及繁殖．结果表明,该轮虫种群在ＰＨ６．５～８．５之间增 长较快, ８． ５时增长最快,即瞬时增长率 ｒ和种群密度较大和最大; ｐＨ在 ３． ５～４． ５和 ９． ５ ～１０． ５之间,种群为负增长,即 ｒ为负值; ｐＨ在 ５． ５～９． ５之间种群为正增长,即正为正 值．该轮虫存活的ｐＨ上限为１１．５,下限为３．５．在种群增长最适ｐＨ（８．５）条件下,该轮虫 的繁殖最快,即绝对带卵量最高（１３２个·ｍｌ－１）;ｐＨ在９．５时,其相对带卵量最高．为其它 ｐＨ值条件下的２～４倍．本研究结果可为淡水轮虫的大批量培养提供可靠的ｐＨ值技术指 标．     

食物种类和浓度对壶状臂尾轮虫实验种群动态的影响

使用浓度为0.3mg/mL的椭圆小球藻、尖细栅藻和两者以1:1(湿重比)组成的混合藻在26±1℃下对壶状臂尾轮虫进行单个体培养研究。结果表明,虽然三类食物对轮虫的胚胎发育时间和平均寿命无显著影响,但投喂小球藻时轮虫的生殖前期明显比投喂栅藻或混合藻时短,投喂小球藻时轮虫的生殖期明显比投喂栅藻时长;轮虫的生殖后期历时以栅藻组最长,混合藻组次之,小球藻组最短,三者间具显著差异。轮虫的繁殖率、产卵量和种群内禀增长率均以小球藻组最高,混合藻组次之,栅藻组最低。由此可见,小球藻是该种轮虫培养的最适饵料。以浓度为0.375、0.75、1.5、3.0和5.0×106cells/mL的椭圆小球藻为食物在23±1℃下对壶状臂尾轮虫进行单个体培养研究发现,0.75×106cells/mL是其生存和繁殖的最低浓度阈值;食物浓度对轮虫的胚胎发育时间和生殖后期历时无显著影响;食物浓度为1.5×106cells/mL和3.0×106cells/mL时,轮虫各主要发育阶段的历时和产卵量间也无显著差异;食物浓度高于3.0×106cells/mL或低于1.5×106cells/mL对轮虫的生殖前期无显著影响,但使轮虫的平均寿命和产卵量显著减小;食物浓度高于3.0×106cells/mL时,轮虫的生殖期显著缩短。轮虫种群的繁殖率、净生殖率和内禀增长率皆以3.0×106cells／mL组最高,1.5×106cells／mL组次之,0.75×106 cells／mL和5.0×106cells／mL组较低。因此,轮虫种群增长的适宜食物浓度范围为1.5-3.0×106cells／mL,最适食物浓度是3.0×106cells／mL。       

密度信号对两种臂尾轮虫种群增长的影响

为了更好的了解化学干扰对轮虫种间竞争的影响,分别用萼花臂尾轮虫(Brachionus calyciflorus)和角突臂尾轮虫(Brachionus angularis)研究了同种和异种种群密度信号对种群增长的影响。结果表明,密度信号对轮虫种群增长具有一定的影响。萼花臂尾轮虫的密度信号显著降低了本种和角突臂尾轮虫种群的环境容纳量K并提高了它们的种群增长率r(P0.05),角突臂尾轮虫的密度信号对本种和萼花臂尾轮虫的种群增长都没有显著影响(P0.05)。萼花臂尾轮虫种群增长受同种密度信号抑制十分显著,环境容纳量K降低了50%以上,可能主要受自毒作用的调节,但同种密度信号对高有性生殖的萼花臂尾轮虫种群的混交率影响不明显。角突臂尾轮虫几乎不受自身密度信号的影响。因此,在两种臂尾轮虫的竞争中,由于自身密度信号的抑制作用,萼花臂尾轮虫将更快被角突臂尾轮虫排除。据此可推测密度信号对轮虫的种间竞争具有重要影响。     

食物种类对萼花臂尾轮虫种群增长率的影响

在短期慢性观测过程中,食物类型可能是造成萼花臂尾轮虫(Brachionuscalyciflorus)种群繁殖率变化的一种原因。共观测了分别单独投喂10种不同绿藻对轮虫种群增长率的影响。为验证藻青菌是藻类饵料(如绿藻Scenedesmus)有价值的佐剂这一假说,还用蓝细菌单独投喂或与斜生栅藻(Scenedesmusobliquus)混合投喂轮虫进行实验观测。结果发现食物种类对萼花臂尾轮虫种群增长率影响显著。斜生栅藻组获得最大种群增长(1.6/d),而Desmodesmus组增长率最低(0.3/d)。以占斜生栅藻组最大增长的百分率来表示,其它几种绿藻组种群增长由高到低依次为:Desmodesmussubspicatus88%,小球藻(Chlorellavulgaris)83%,单壳缝藻(Monoraphidiumminutum)77%,D.quadricauda74%,S.falcatus71%,S.acuminatus69%,S.pectinatus64%,莱茵衣藻(Chlamydomonasreinhardtii)57%,D.abundans19%。轮虫增长率的差异不能用藻类饵料的大小差异来解释。蓝细菌(Microcystisaeruginosa)和(Synechococcuselongates)不论是单独投喂还是与优良藻类饵料(斜生栅藻)混合投喂都对萼花臂尾轮虫种群增长有抑制作用。这种副作用似乎与微囊藻素无关。该结果不支持无毒蓝细菌可作为与其他绿藻饵料配合使用的优良佐剂这一假说。本研究所观察到的生长变化显示了饵料种类对萼花臂尾轮虫种群增长的影响,也预示了对毒性实验结果的影响     

溴氰菊酯对萼花臂尾轮虫实验种群动态的影响

采用生命表技术对暴露于不同浓度溴氰菊酯溶液中的萼花臂尾轮虫的存活和繁殖进行了研究。结果显示, 溴氰菊酯使轮虫的存活时间显著缩短, 繁殖率降低; 当溴氰菊酯浓度高达3 6 mg/L时, 轮虫的存活时间最短、繁殖率最低。与对照组相比, 除1 2 mg/L外, 其它各浓度的溴氰菊酯均使轮虫的生殖前期显著延长; 浓度为0 6和1 2 mg/L的溴氰菊酯使轮虫的生殖期显著延长, 而浓度为2 4和3 0 mg/L的溴氰菊酯却使轮虫的生殖期显著缩短; 1 2 mg/L的溴氰菊酯使轮虫的平均寿命显著延长。轮虫的生命期望、世代时间、净生殖率和种群内禀增长率均随溴氰菊酯浓度的升高而下降。当溴氰菊酯浓度升高达1 2 mg/L时, 轮虫的净生殖率开始与对照组有显著差异; 而轮虫的种群内禀增长率从溴氰菊酯浓度升高达2 4 mg/L时才开始与对照组有显著差异。在溴氰菊酯的毒性监测中, 净生殖率是比种群内禀增长率更敏感的指标。     

萼花臂尾轮虫有性生殖、种群增长和休眠卵产量间的关系

利用种群指数增长和Logistic增长模型,通过计算机模拟研究了萼花臂尾轮虫有性生殖发生的频率,后代中的混交雌体发率对种群增长和休眠卵产量的影响。在所模拟的参数范围内,随有性生殖发生频率由100％减小到20％,获得了大休眠卵产量所需的混交雌体百分率由9％增大到69％,随密度制约作用的增大（环境容纳量K值由1000减小到100）,该混交雌体百分率由18％增大到69％,休眠卵产量由1072．10降低至133．67,种群的内禀增长率与获得最大休眠卵产量所需的混交雌体百分率间呈曲线相关。当有性生殖发生得越频繁,种群增长所受的密度制约作用较小时,后代中10％－30％的个体为混交雌体时的种群中休眠卵产量较大。     

温度对萼花臂尾轮虫卵的发育、种群增长和生产量的影响

1981—1983年,在不同的培养温度下,观察了萼花臂尾轮虫(Brachionus calyeiflorus)卵的发育时间、种群的增长并用3种不同方法测算生产量。在5—30℃的培养温度下,轮虫卵的发育时间(D)随温度(T)升高而缩短,其曲线迴归方程为：LnD;=2.0539 0.1097LnT-0.3046(LnT)^2在10,15,20,25℃的培养温度下,从休眠卵孵化出来的孤雌生殖雌体,其繁殖的种群增长曲线都呈“S”形,或称逻辑斯蒂曲线(Logistic curvc)。不同的温度,种群达到高峰所需的时间有所不同,温度高者短,低者长;容纳量(carrying capacity)却随温度增加而有所增加。用线性和指数方法计算轮虫种群的生产量所得的结果相似;而与世代时间方法计算所获得的结果相比,差距很大。这种差距随着温度增加而增加。根据本文的研究结果和文献中报道的数据,获得了在0．6—35．2℃温度范围内,卵的发育时间(D)与温度(-I)之间的迴归方程：LnD=2.1869—0．1919LnT-0.2218(LnT)^2     

食物浓度对方形臂尾轮虫发育历期与实验种群增长参数的影响

为探讨富营养化水体中大量发生的轮虫与微藻之间的关系 ,在实验室条件下 ,观测了不同藻类食物浓度下方形臂尾轮虫生命周期中各发育阶段的历时以及种群增长参数的变化。实验选用蛋白核小球藻为食物 ,浓度梯度为 0 1× 10 6、 0 5× 10 6、 1 0× 10 6、 2 0× 10 6、 4 0× 10 6、 8 0× 10 6、 12× 10 6cells/ml。结果表明 :食物浓度对方形臂尾轮虫的胚胎发育时间与繁殖前期历时、产卵量、世代净生殖率、世代时间和种群的内禀增长率均有明显影响。在食物浓度为 2 0× 10 6cells/ml时 ,方形臂尾轮虫的繁殖前期最短 ,产卵量最大 ,世代净生殖率和种群增长率最高 ,世代时间最短。方形臂尾轮虫可在高于其最适食物浓度的较宽的食物浓度范围内 ,保持较高的种群增长率 ,表现出较强的对环境中高浓度藻类的适应     

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。     

pH对5种臂尾轮虫后代存活率和混交雌体率及种群内禀增长率的影响

水生生态系统中,pH是重要的非生物因子之一.pH可以通过影响水生生物的存活和繁殖,进而影响其在水体中的分布和多度,最终决定水生群落的物种组成和丰富度[1].     

Effect of pH on survival,reproduction, egg viability and growth rate of five closely related rotifer species

In the laboratory we examined the effect of pH (5–10 with one interval) on survival, reproduction, egg viability and growth rate (intrinsic growth rate—r _m and population growth rate—r) of five Brachionus rotifer species (B. calyciflorus, B. quadridentatus, B. urceolaris, B. patulus and B. angularis). The pH was shown to exert a major influence on egg viability and growth rate (r _m and r) for each species. The age-specific survivorship curves within a species were not significantly different at pH 6–10. The optimal pH for each species is near-neutral pH (pH 6–8), and the fecundity decreased as the pH deviated from these values. For each Brachionus species, there was no significant difference between age-specific fecundity curves at pH 7 and 8. At acid pH (pH 5 or 6) higher egg mortality was observed for each species. The r _m and population r of the five Brachionus species incubated at different pHs were significantly influenced by pH. The pH supporting the highest r _m or r was obtained at pH 6–8, but varied due to species. In this study B. urceolaris and B. patulus could tolerate a broad range of pH, while the populations of B. calyciflorus, B. quadridentatus and B. angulari declined at acid conditions.     

Effects of three organophosphorus pesticides on population growth and sexual reproduction of rotifer Brachionus calyciflorus Pallas

Effects of organophosphorus pesticides including dichlorvos, triazophos and chlorpyrifos on population growth and sexual reproduction of freshwater rotifer Brachionus calyciflorus were studied by 3-d population growth and 4-d resting egg production tests. The results showed that all the three organophosphorus pesticides influenced significantly the population growth rate, the ratio ovigerous females/non-ovigerous females in the rotifer populations and the resting egg production of the rotifers. Both dichlorvos and chlorpyrifos influenced markedly the mictic rate of the rotifers, but triazophos did not. Compared to the controls, both dichlorvos at 10.0–1000.0 μg/L and chlorpyrifos at 0.01–100.0 μg/L increased the population growth rate, but the reverse was also true for dichlorvos and triazophos both at 10000.0 μg/L. Chlorpyrifos at 10000.0 μg/L made the rotifers dead after 24-hr exposure. Dichlorvos and triazophos both at 10000.0 μg/L, and chlorpyrifos at 1000.0 μg/L all increased the ratio ovigerous females/non-ovigerous females. Both dichlorvos at 10000.0 μg/L and chlorpyrifos at 0.1–100.0 μg/L increased the mictic rate. Dichlorvos at 10.0 μg/L and 100.0 μg/L, and triazophos and chlorpyrifos both at 0.1–100.0 μg/L increased the resting egg production. Both population growth rate and ratio ovigerous females/non-ovigerous females are suitable endpoints for assessing the effects of dichlorvos, triazophos and chlorpyrifos, and mictic rate is a suitable endpoint for monitoring the effects of dichlorvos and chlorpyrifos on the reproduction of the rotifers. Both population growth rate and ratio ovigerous females/non-ovigerous females are more sensitive to dichlorvos and chlorpyrifos than mictic rate.     

不同pH条件下5种臂尾轮虫（Brachionus）的生殖代价

研究了5种臂尾轮虫(萼花臂尾轮虫、方形臂尾轮虫、壶状臂尾轮虫、十指臂尾轮虫和角突臂尾轮虫)在不同pH条件下(pH 5, 6, 7, 8, 9, 10)当前繁殖(mx)与未来存活(lx 1)、未来生殖(mx 1)和残余生殖价(V*x)的相关关系.结果表明,5种臂尾轮虫存活代价的相关系数在初始几个日龄组表现为正相关或负相关,在随后的大部分日龄组中,均表现为负相关,直至整个生命周期.相对于存活代价,5种臂尾轮虫繁殖代价和残余生殖代价的相关系数的变化幅度较大,但整体趋势仍就是大部分呈现负相关.因此可以推断,轮虫在不同pH条件下存在存活代价、繁殖代价和残余生殖代价.mx与lx 1对日龄组的回归分析有100%回归关系显著,mx与mx 1有97%回归关系显著,而mx与V*x有93%回归关系显著.因此推断,轮虫在不同pH条件下存活代价、繁殖代价和残余生殖代价的负相关性随着日龄组的增加而逐步增加.结果还发现,某些种类的轮虫(方形臂尾轮虫、壶状臂尾轮虫和十指臂尾轮虫)在胁迫的pH(酸性或碱性)条件下,其存活代价、繁殖代价和残余生殖代价较适宜pH(中性)条件下更为显著.     

Effect of unionized ammonia,viscosity and protozoan contamination on reproduction and enzyme activity of the rotifer Brachionus rotundiformis

We determined the effect of environmental stressors on the physiological condition of Brachionus rotundiformis. For two morphologically distinct B. rotundiformis strains: Hawaii (average lorica length = 222 m) and Langkawi strains (average lorica length 180 m), neonates hatched from resting eggs were exposed to different levels of unionized ammonia (0.7–9.8 mg l^–1), viscosity (relative viscosity against natural seawater = 1–1.17) and Euplotes sp. (protozoan) contamination (1–40 cells ml^–1). Increasing stress decreased fecundity and lifespan of both rotifer strains. Glucosidase and phospholipase activities were correlated with reproductive responses of both the strains exposed to unionized ammonia. When culture water viscosity was changed, the activity of esterase and phospholipase was correlated with reproductive responses of the Hawaiian strain, and glucosidase activity was correlated with those of Langkawi strain.With the protozoan contamination, esterase and glucosidase activities were correlated only with reproductive responses of the Hawaiian strain, while activity of all three enzymes was correlated to those of the Langkawi strain. Glucosidase activity proved to be a reliable indicator of stress for cultured B. rotundiformis.     

Nutritional effect of freshwater Chlorella on growth of the rotifer Brachionus plicatilis

Mass production of Brachionus plicatilis is usually accomplished by feeding so-called marine Chlorella (Nannochloropsis oculata) to the rotifers in marine fish hatcheries. If the marine Chlorella are in short supply, baker's yeast is usually used as a supplementary food. Recently, a condensed suspension of freshwater Chlorella (Chlorella vulgaris, k-22) was commercially developed as another supplementary food. We have evaluated the dietary value of this freshwater Chlorella for growth of the rotifer by means of individual and batch cultures. Rotifers cultured with the freshwater Chlorella suspension under almost bacteria-free conditions, showed very suppressed growth. However if the Chlorella was supplemented with vitamin B₁₂ by adding the vitamin solution into the suspension or by culturing the Chlorella in a medium containing vitamin B₁₂, the nutritional value of freshwater Chlorella was greatly improved and almost at the same level as that of marine Chlorella. Condensed Chlorella may therefore be effective as a supplementary food if vitamin B₁₂ is supplied.     

Bacterial feeding by the rotifer Brachionus calyciflorus: Clearance and ingestion rates,behavior and population dynamics

Summary The rotifer Brachionus calyciflorus is capable of collecting and ingesting cells or short chains of a laboratory-grown bacterium Aerobacter aerogenes. Clearance rate, the volume of water effectively processed animal ^-1h^-1, does not vary systematically with bacterial density between 0.01 and 100 g dry weight ml^-1. Consequently, ingestion rates are strongly density-dependent, reaching maximal values at the highest food densities tested. Bacterial feeding rates are consistently lower than those determined with larger food types, except in very dense cell suspensions. A. aerogenes in high concentration (100 g ml^-1) induces Brachionus to orient their pseudotrochal cirri to form screens over the buccal funnel; this behavior is at least four times less frequently observed at low (10 g ml^-1) food density. Despite its occurrence, pseudotrochal screening appears ineffective in regulating bacterial ingestion rate. B. calyciflorus can be cultured xenically for greater than 40 generations fed A. aerogenes alone, with no diminution in net reproductive rate or intrinsic rate of natural increase, and no lengthening in cohort generation time.     

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.