Infectious diseases affecting mass production of the marine rotifer Brachionus plicatilis

During recent years, investigations on decrease ofrotifer density in culture tanks from severalhatcheries have shown that infectious diseases mightbe associated with abnormal mortality. The firstreported infection was caused by an unusual birnavirusreferred as rotifer birnavirus (RBV). Viral lesionsappeared in cells of gastric glands and spread toother epithelia. Virus particles were also foundwithin ovarian cells. Highly infected rotifersexhibited abnormal behavior and died. The secondimportant pathogen found in Brachionusplicatilis has been provisionally related to theLagenidiaceae. The fungus developed in up to 85% ofrotifers and caused sudden, precipitous decrease inanimal density. The occurrence of these diseases showsthat in the future infectious agents will have to beconsidered as important factors capable of reducingthe productivity of rotifer mass cultures.     

营养强化时褶皱臂尾轮虫对饵料微藻的摄食

选取适宜浓度利用单种微藻和混合微藻对轮虫进行营养强化,采用实验生态学方法研究了轮虫滤水率和摄食率的动态变化.结果表明:微藻浓度、微藻种类和培养时间均对轮虫的滤水率和摄食率有显著影响;轮虫对几种单种微藻的滤水率和摄食率均随培养时间的延长而下降,在实验条件下,6h内轮虫对3种微藻的滤水率大小顺序为小球藻＞球等鞭金藻＞牟氏角毛藻,12h内轮虫对3种和,微藻的滤水率大小顺序则为球等鞭金藻＞小球藻＞牟氏角毛藻;轮虫在混合微藻中的选择顺序为球等鞭金藻＞小球藻＞牟氏角毛藻.     

Interspecific interactions in the marine rotifer microcosm

Copepods and protozoans often co-exist in marinerotifer mass cultures. Interspecific interactionbetween the rotifer Brachionus rotundiformisTschugunoff and eight other zooplankton species,namely Brachionus plicatilis O. F. Müller (rotifer),Diaphanosoma celebensis Stingelin (cladoceran),Tigriopus japonicus Mori, Acartia sp. (copepod),Euplotes sp., Vorticella sp., an unidentifiedprotozoan species (P1 strain) (protozoan) and Artemiasp. (anostracan) at two developmental stages (nauplii –0.95 mm, 0 days old; adults – 3.3 mm, 19 days old) wereinvestigated in the laboratory.There was no contaminating species that contributedto an increase in rotifer population growth during theexperiments. Four types of interspecific interactionswere seen between B. rotundiformis and otherco-existing zooplankton species. These include effectson population growth: (1) both species declined, (2) onespecies is promoted while the other is not influenced,(3) one species is declined while the other is notinfluenced and (4) one species is promoted while theother declined. The first type was exhibited by B. rotundiformis vs B. plicatilis, B. rotundiformis vsD. celebensis and B. rotundiformis vs Artemia sp. The second type was exhibited by B. rotundiformis vsVorticella sp. and the third type by B. rotundiformisvs Euplotes sp. and B. rotundiformis vs T. japonicus. The fourth type was exhibited by B. rotundiformis vs Acartia sp. and B. rotundiformis vs P1 strain.     

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.     

塔玛亚历山大藻和东海原甲藻对褶皱臂尾轮虫种群数量的影响

通过对2002年5月东海赤潮原因种一东海原甲藻和亚历山大藻的单一藻种和两种藻混合情况下对褶皱臂尾轮虫种群数量影响的实验研究,发现塔玛亚历山大藻(ATHK)对轮虫有致死作用,其48hLC50为1300cell·ml^-1．藻的各组分毒性比较研究表明,只有藻液和藻细胞具有这种毒害作用,藻在早期生长阶段的毒害作用较强,毒性大小与藻细胞活性相关．东海原甲藻在高密度(4×10^4、5×10^4、10×10^4cell·ml^-1)时对轮虫种群数量在第5d时开始有影响;东海原甲藻在低密度(1×10^4、2×10^4、3×10^4cell·ml^-1)时,轮虫能够以其为食并进行生长繁殖．两种藻混合情况下,东海原甲藻能够减轻塔玛亚历山大藻对轮虫的毒害作用．实验结果表明,此次赤潮对东海的微型浮游动物种群能够产生一定的影响．     

萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻群体形成及生长的影响

为探索浮游动物和藻类之间可能存在的信息传递,研究了萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻的生长及群体形成的影响.把萼花臂尾轮虫按1000个·L^-1的初始密度置于小球藻中培养24h后,用孔径0.15μm的微孔滤膜抽滤,得到轮虫培养滤液,此滤液中含有轮虫在生活过程中释放的一些信息化学物质.将轮虫培养滤液以20%的比例分别加入纯培养的铜绿微囊藻、斜生栅藻和小球藻中,进行为期7d的试验.结果表明,萼花臂尾轮虫培养滤液能显著地促进斜生栅藻的群体形成,而对铜绿微囊藻和小球藻在群体形成方面没有显著作用.另外,该滤液能显著提高小球藻种群的增长,对铜绿微囊藻和斜生栅藻的生长无明显影响.3种藻类对萼花臂尾轮虫的潜在牧食采取了不同的生态策略:斜生栅藻形成群体,增大摄食阻力,从而降低被摄食的风险;小球藻通过提高增长率来抵消被取食的损失;铜绿微囊藻是通过其它方式来降低被牧食(例如毒素).这些方式分别是这些藻类维持种群规模的反牧食防御策略之一.     

赤潮藻塔玛亚历山大藻对褶皱臂尾轮虫生活史特征的影响

采用生命表方法,研究了不同浓度塔玛亚历山大藻对褶皱臂尾轮虫生命周期中各发育阶段历时以及种群增长参数的影响．结果表明：塔玛亚历山大藻对褶皱臂尾轮虫的生长发育有明显影响,使轮虫的繁殖前期和世代时间延长,繁殖期、繁殖后期和平均寿命缩短,产卵量和繁殖率降低．轮虫的净生殖率和内禀增长率均低于对照．不同藻浓度下轮虫能够维持一定的种群增长．     

Electrotransformation of Chlorella vulgaris

Using hygromycin B resistance as a marker for selection, we have established the conditions required for the transformation of Chlorella vulgaris. The exponentially grown C. vulgaris cells were transformed by electroporation with plasmid pIG121-Hm, and transformants were selected with hygromycin B at a concentration of 50 μg/ml. Cell extracts prepared from the late-log cultures of the transformants exhibited glucuronidase activities as conferred by the gus gene on pIG121-Hm. The maintenance of plasmid in the algal cells seemed to be transient as many cultures derived from the hygromycin B-resistant colonies gradually lost the hygromycin resistance upon prolonged growth. The result of Southern blotting of the genomic DNAs prepared from transformant cultures exhibiting persistent hygromycin resistance showed that integration of part of the plasmid DNA into the host chromosome had taken place. Received: 19 December 1997 / Revision received: 5 October 1998 / Accepted: 27 October 1998     

Protein and lipid content of the rotifer Brachionus plicatilis during variable growth and feeding condition

Rotifers (Brachionus plicatilis) grown atdifferent growth rate ( = 0.05–0.39 d^–1)were analyzed for protein, lipid, fatty acids, aminoacids and free amino acids, and values are expressedin terms of individuals and dry weight. Increase ingrowth rate is equivalent with increased food rationof the individual rotifer, which responded by higheregg ratio. The protein content per individualrotifer increased by 60–80% when the growth rate increased, whereas the protein content per dryweight showed a slight, although insignificant,increase (p > 0.05). The lipid content perindividual was constant, whereas lipid per dryweight decreased when the growth rate increased. Theratio DHA/EPA decreased when the growth ratesincreased. The amino acids profile in percent oftotal amino acids showed low variation betweencultures maintained at different growth rates,whereas the values expressed in terms of amino acidper individual showed higher variation. The range ofvariation for free amino acids was more pronouncedthan for total amino acids.Short-term food enrichment of poorly fed rotifers( = 0.05 d^–1) with balanced protein richdiet resulted in increased protein and lipid contentper rotifer. The protein content per dry weightshowed only minor changes whereas lipid per dryweight increased. Contrary, short term enrichmentwith a lipid rich diet resulted in increased lipidcontent per individual rotifer and per dry weight,whereas the protein content per individual remainedconstant and the protein content per dry weightshowed a slight decrease.Our experiments show that the amount of protein, wasquite variable in rotifers, and that feeding andgrowth condition were decisive factors affecting it.The range of variation was large enough to be animportant factor during first feeding of marinelarvae, and should therefore be considered infeeding larvae.     

Live food production using batch culture and chemostat systems in Kuwait

A comparison of live food production using batch andchemostat systems between the facilities initiated in1988 and the re-establishment of new larger chemostatsystems, after Kuwaits liberation, is made. The livefood production dynamics achieved during the 1995–1996 spawning season of Shaem (Acanthopagrus latus)are discussed. Growth rate of the rotifers (Brachionusplicatilis) treated 24 h with a mixture of marinealgal species (Nannochloropsis, Isochrysis,Tetraselmis, Chlorella) plus other enrichment mediasuch as Super Selco, Protein Selco and Sanders priorto being supplied to the marine fish larvae isdiscussed. Rotifer production reached up to 2000 ×10⁶ individuals per day.     

Optimization of pH induced flocculation of marine and freshwater microalgae via central composite design

Microalgae harvesting via pH induced flocculation along with utilization of recovered medium after flocculation is one of the most economical methods for separating the microalgal biomass in order to reduce the dewatering cost. In this study, optimization of marine and freshwater microalgae flocculation by pH adjustment was investigated via central composite design methodology. One molar of KOH and NaOH solutions were used to increase the pH level of the microalgal culture. Increasing pH value of the medium provided the highest flocculation efficiency up to 92.63 and 86.18% with pH adjusted to 10.5 with KOH and NaOH solutions for marine microalgae Nannochloropsis oculata and freshwater microalgae Chlorella minutissima, respectively. Also, it was revealed that microalgae cells were still alive after flocculation process and their biochemical composition was not changed, and flocculated medium can be used again for the next microalgal production. According to the results, it can be said that this method is cheap and effective, simple to operate and provides the utilization of flocculated medium again.     

谷氨酸对异养培养小球藻生长的影响

在不添加其他氮源的小球藻异养培养基中,谷氨酸可促进小球藻的生长,但基本不增加叶绿素的合成;在以铵盐为氮源时,谷氨酸可明显促进小球藻对铵盐的利用,促进小球藻生物量增加和叶绿素合成;在以硝酸盐为氮源时,谷氨酸可增加小球藻的生物量,对叶绿素含量无明显影响。     

Production and nutritional quality of the rotifer Brachionus plicatilis fed marine Chlorella sp. at different cell densities

The effect of different cell densities of marine Chlorella sp. on the growth rate, doubling time and production of the rotifer Brachionus plicatilis was investigated. A significant increase in rotifer production was achieved at a density of 50 × 10⁶ Chlorella cells ml^–1. The nutritional quality of rotifers grown at different concentrations of Chlorella is discussed.     

磁处理对小球藻超微结构的影响

用透射电镜研究在不同强度磁场处理下,小球藻超微结构的变化。结果显示:磁处理强度不同,小球藻细胞亚显微结构变化程度不同。细胞壁、叶绿体、线粒体和液泡等部位是受磁处理影响的主要部位。研究发现在较高强度磁处理下,出现质壁分离,类囊体结构轻微破坏,液泡和线粒体增加,能量物质积累等现象,影响小球藻的正常代谢。     

Does excess carbon affect respiration of the rotifer Brachionus calyciflorus Pallas?

1. Herbivorous zooplankton maintain a rather constant elemental composition in their body mass as compared with the variability commonly encountered in their food. Furthermore, their high phosphorus (P) and nitrogen (N) content means that they often face an excess of carbon (C) in their diet. Regulation of this surplus of energy may occur via modulation of assimilation efficiency, or postassimilation by increased respiration (CO₂) and/or excretion dissolved organic carbon, DOC. Whereas several studies have examined the effect of elemental imbalance in the genus Daphnia, few have examined other zooplankton taxa. 2. We investigated whether the rotifer Brachionus calyciflorus uses increased respiration as a means of stoichiometrically regulating excess dietary C. Growth rate and respiration were measured under different food qualities (C : N and C : P ratios). 3. Both C : N and C : P ratios in food had strong effects on growth rate, demonstrating strong nutrient limitation of rotifer growth when nutrient elements were depleted in the diet and indicating the need for stoichiometric regulation of excess ingested C. 4. Respiration measurements, supported by a stoichiometric model, indicated that excess C was not released as CO₂ in B. calyciflorus and that nutrient balance must therefore be maintained by other means such as excretion of DOC or egestion in faecal material.     

小球藻对镉离子的吸附速率方程

研究了小球藻对Cd^2 的吸附动力学。研究表明,小球藻对Cd^2 有一定的吸附作用,在吸附的起始阶段,吸附速率较快,且随温度的升高吸附速率增大,吸附过程在20min内达到平衡。结果还表明,该吸附是简单的一级反应,并由此建立了吸附反应的速率方程,推算出吸附反应的活化能Ea=31．42kl／mol。     

植物激素在小球藻异养培养中的作用

本文研究了几种植物激素对小球藻异养培养的影响。结果表明 ,IAA、IBA及 6_BA三种植物激素均不同程度地促进了小球藻的异养生长 ,培养≤ 36h时 ,IAA或IBA以 2 0mg/L的促进小球藻异养生长的效应最大 ,1 0 0mg/LIAA或IBA则抑制了藻的生长 ;>36h时 ,1 0 0mg/LIAA或IBA表现出促进小球藻生长的效应 ,并最终获最大净A540 增长量 ;6_BA以 0 1mg/L的促进作用最大。IBA与 6_BA组合同样表现出促进小球藻异养生长的效应 ,但并非IBA和 6_BA简单的加合效应 ,5mg/LIBA与 6_BA组合的效应维持 6_BA单因子的作用趋势 ,2 0mg/LIBA与 1mg/L 6_BA组合的效应大于与 0 .1mg/L 6_BA组合的 ,1 0 0mg/LIBA与 0 .1mg/L 6_BA组合的效应在≤ 36h时大于与 1mg/L 6_BA组合的 ,>36h时则相反。另外 ,高浓度IBA(≥ 2 0mg/L)与 6_BA组合抑制了前中期异养藻对葡萄糖的吸收 ,但加速了中后期葡萄的吸收。再者 ,IBA与 6_BA组合加速了异养小球藻对NO_3 的吸收。     

Factors affecting low temperature preservation of the marine rotifer Brachionus rotundiformis Tschugunoff

Experiments were performed to determine suitable conditions for low temperature preservation of small S (Fukuoka) and ultra-small SS (Thai) strains of B. rotundiformis. For this, single rotifers (an adult bearing one egg or a 4-h neonate) were incubated for 10 days in 1 ml seawater (22 ppt salinity). The highest survival was achieved at 10 and 12 °C for S-strain and 12 °C for SS-strain. The effect of salinity, change of culture medium and feeding regime were further tested on rotifers (300 ind. ml^–1) cultured in vials containing 10 ml seawater and microalgae at 12 °C. Survival of S-strain was highest (55.5±0.8%) at 35 ppt, while SS-strain survived best (43.1±2.6%) at 17 ppt. Survival was suppressed by changing the culture medium every 4 days. Feeding rotifers every 2 days yielded better survival (66.2±6.6%: S-strains, cultured at 35 ppt and 81.8±5.2%, SS-strains cultured at 17 ppt) than feeding them only at the beginning of the experiment or at 4-day intervals. An acclimation at 20 °C for 24 h before transferring them from their usual culture temperature (28 °C) to 12 °C resulted in higher survival of SS-strain. For S-strain, however, no significant improvement resulted from acclimation. SS-strain was more susceptible to lower temperature and higher salinity than S-strain.     

一种高效提取普通小球藻叶绿体DNA的新方法

本文采用尿素-月桂酰肌氨酸钠（urea-sarkosyl）法, 用于分离带有坚硬细胞壁小球藻的高纯度叶绿体DNA （cpDNA）。将对数生长期的小球藻收集后置于冰上研磨, percoll密度梯度离心收集叶绿体层, 显微观察表明叶绿体经梯度离心后形态完整。采用尿素-月桂酰肌氨酸钠法、蛋白酶K消化及酚/氯仿/异戊醇抽提, 获得了高纯度的cpDNA。检测结果显示, cpDNA分子长度为22 kb, A260：A280值为1.87±0.01, 产率达（2.52±0.01） μg？g-1 （DW）; cpDNA编码的16S rDNA扩增呈阳性, 而由细胞核编码的18S rDNA扩增呈阴性。表明cpDNA纯度高, 没有受到核基因组DNA的污染, 符合小球藻cpDNA高通量测序的要求。同时, 该方法也适合提取具有相似细胞壁成分的其他微藻的基因组DNA和cpDNA。     

热带普通小球藻培养模式的筛选及其培养基的优化

【背景】从海南热带海区中分离得到一株微藻,其生长速度快、适应力强,经鉴定该微藻为普通小球藻。【目的】提高热带普通小球藻的生长速率。【方法】以"宁波大学3#微藻培养液配方"为基础培养液,分别添加有机碳(C6H12O6和CH3COONa)对热带普通小球藻进行自养、兼养及异养培养,获得促进热带普通小球藻快速生长的培养方式。在"宁波大学3#微藻培养液配方"的基础上对热带普通小球藻的兼养培养基配方进行优化,并用优化兼养培养基与"宁波大学3#微藻培养基"对比培养热带普通小球藻。【结果】添加6 g/L CH3COONa的兼养模式促进热带普通小球藻生长效果最好;优化的兼养培养基配方为:6 g/L CH3COONa,20 mg/L(NH4)2SO4-N,5 mg/L Na H2PO4-P,3 mg/L Fe SO4-Fe,1 mg/L Vitamin B1和0.000 5 mg/L Vitamin B12。对比培养实验结果显示,培养第6天,兼养培养液收获的生物量(细胞密度)达4.20×107 cells/m L,是"宁波大学3#配方微藻培养液"的2.30倍。【结论】兼养培养模式为热带普通小球藻的最佳培养模式,优化的兼养培养基极显著地提高了热带普通小球藻的生物量(P0.01)。