Low-temperature preservation (at 4 °C) of marine rotifer Brachionus

Mass production of rotifers is essential as live food during the larval rearing season, but a major problem of rotifer culture is unpredictable culture collapse. If mass‐produced rotifers could be kept alive at low temperature for an extended period of time, they could be supplied as live food to cultured marine fish larvae without interruption. Four experiments were performed to test this possibility in six strains of Brachionus plicatilis O. F. Müller and eight strains of Brachionus rotundiformis Tschugunoff. The results showed that: (1) B. rotundiformis strains were less tolerant to 4 °C than B. plicatilis strains. Among the B. rotundiformis strains, the strains known as SS type were the most susceptible and showed the lowest survival. (2) Exchange of culture media during the incubation at 4 °C in B. plicatilis and B. rotundiformis resulted in higher survival than not changing the culture media, but there were no differences in the regression slope with or without changing the culture media. (3) Acclimation at 15 °C for 96 h for B. plicatilis and B. rotundiformis before transfer to 4 °C resulted in higher survival rates than acclimation at 10 °C. (4) The combination of frequent exchange of culture media and acclimation significantly improved the survival of B. plicatilis and B. rotundiformis compared with controls that were maintained at 4 °C without exchange of the culture media. Large‐scale trials using B. plicatilis (Kamiura strain) cultured in 30‐L tanks were conducted in a hatchery at a density of 2000–20 000 individuals mL^?1. Rotifers were transferred directly from 25 °C to 4 °C. About 50% of the rotifers at 20 000 individuals mL^?1 survived after 14 days at 4 °C. These preserved rotifers could be cultured at 20 °C, recovering within 4 days.     

轮虫培养过程中生长及环境变化特征分析

通过1000ml烧杯、5L全自动生物反应器、常规的大池（5m^3）以及加处臭氧和生物过滤装置的大池（约5m^3）这四种培养系统,对在轮虫培养过程中轮虫的生长特征,以及pH、溶氧、氨氮及亚硝态氮等水质参数变化特征进行了较系统的探讨,研究结果可为轮虫密度培养工艺及培养系统的优化奠定基础。     

不同脂肪源对褶皱臂尾轮虫脂类和脂肪酸组成的影

以褶皱臂尾轮虫（Brachionus plicatilis)为实验动物并设计不同脂肪源饵料，分别为：面包酵母Saccharomyces cerevisice（对照组），微绿球藻Nannochlorpisis oculata(A)，5%大豆磷脂 5%鱼油 90%面包酵母（C）。结果表明：（1）接受不同脂肪源的轮虫的脂肪酸组成显著不同，尤其是高度不饱和脂肪酸（HUFA，20C）含量存在显著差异，说明饵料中HUFA含量对轮虫体内相应脂肪酸的含量有显著影响。投喂饵料C使轮虫的脂类HUFA水平得到了强化，提高了轮虫的营养价值。（2）轮虫脂类的HUFA水平不仅由饵料中脂类的相应脂肪酸组成决定，而且轮虫脂类HUFA的提高和强化效果与饵料中HUFA的化学形态密切相关。甘油三酯型饵料HUFA的强化轮虫效果高于磷脂型的HUFA。（3）将富含HUFA的鱼油直接添加在干性饵料如面包酵母中，而不是通过对鲁油乳化后直接强化轮虫，同样能取得良好的强化效果，且操作简便、不易污染水质，适用于轮虫的规模生产。     

不同饵料对褶皱臂尾轮虫种群生长繁殖的影响↑（*）

用３种饵料、４个组合培养褶皱臂尾轮虫,研究饵料对轮虫种群生长、繁殖的影响。结果表明：用光合细菌和鲜酵母混合为饵组,轮虫的最高培养密度达到了１８２０ｍＬ－１,高于其它３组;轮虫的日平均增殖率为０．４３５１,比光合细菌组和鲜酵母组分别增加了６．４％和２５．０％。对轮虫生长、繁殖有明显的促进作用。     

Comparison of rotifer Brachionus plicatilis as a choice of live feed with dry feed in rearing Coregonus lavaretus fry

This experiment, designed for the first time in the Middle East region to sustain Coregonus lavaretus production, examined the efficacy of a live organism ( Brachionus plicatilis ), an artificial diet (48% crude protein) and a mixed feed for the first 3 month of rearing fry. Nine rearing cages were floated on the surface of a natural pond supplied with hyporheic-zone river water, each containing 150 numbers of white fish fry, where they were treated with each of the three diets in triplicates. The fry were fed eight times daily starting at the onset of exogenous feeding. Results showed that fry utilized live organisms more efficiently than the artificial and mixed diets. Rotifer-fed group consistently showed higher growth rate during the entire experiment. Length increment (29.6 mm), weight gain (572.3 mg) after 12 weeks of feeding were higher ( P  < 0.05) in this group. Also, their mean weekly specific growth rate (4.97% day⁻¹) was the highest and feed conversion rate (2.97) was the lowest among all treatments. Survival rates of the fry declined from 75% to 61.4%, from 74.3 to 45.8% and from 72.7 to 54.5% for live feed, mixed diet and artificial diet, respectively.     

室外轮虫培育池中非生物因子的初步研究

通过对室外轮虫培育池的几个水化学指标的跟踪测定,发现在培养初期,轮虫池的溶氧、pH值都很高。随着轮虫量的增加,溶氧和pH值下降到相对较低水平,氨态氮、活性磷等营养盐量在轮虫大量发生后迅速上升。后期溶氧、pH值上升,氨态氮下降。在培养期间,由于轮虫量变化大,一些主要理化因子的量及变化幅度也随之加大。溶氧的变化范围:2 66～12 7mg L,平均值为6 97mg L;pH的变化范围:8 57～9 60,平均值为8 93;营养盐中氨态氮变化范围:0 26～6 58mg L,平均值为3 77mg L;活性磷变化范围:0 035～1 41mg L,平均值为0 256mg L;CODMn值变化范围:20 8～65 2mg L,平均值为35 17mg L。     

褶皱臂尾轮虫培养若干问题探讨

本文就轮虫生产性培养过程中接种密度、投饵量、水质、轮虫生长和营养强化等方面的问题进行探讨,认为:接种密度在用单胞藻培养时应为10～30个/ml,用酵母培养时20～50个/ml;酵母投喂量0 3～0 35g/百万,投喂量不宜过大;酵母投喂的轮虫使用前2d最好用单细胞藻类强化。     

铜锌离子对褶皱臂尾轮虫的急性毒性试验

研究了Ｃｕ＋＋、Ｚｎ＋＋对褶皱臂尾轮虫（Ｂｒａｃｈｉｏｎｕｓｐｌｉｃａｔｉｌｉｓ）的急性毒性影响。实验温度２５±１℃,轮虫对Ｃｕ＋＋的污染相当敏感,Ｃｕ＋＋２４ｈ半致死浓度为２４ｈＬＣ５０＝１４．４７μｇ／Ｌ～２１．９３μｇ／Ｌ;Ｚｎ＋＋２４ｈ半致死浓度为２４ｈＬＣ５０＝３．４０４ｍｇ／Ｌ～４．５４９ｍｇ／Ｌ。     

褶皱臂尾轮虫高密度培育技术的研究

本文在通过实验确认了褶皱臂尾轮虫的最佳培育水温(28～30℃)和比重(1.015)的条件下,开展了轮虫培育水体的紫外线和臭氧消毒处理、不同换水方式、不同的饵料组合和培育方法等试验,以期达到利用小水体实现轮虫生产性的高密度培养,降低劳动成本和生产时间,保证经济水产动物开口活饵料的供应.结果表明:培育轮虫的水体经紫外线和臭氧消毒处理;混合投喂小球藻、面包酵母和光合细菌;经5～7d的培育后,进行全换水等方法有利于轮虫的繁育和持续生长;轮虫初始接种密度为209个/mL,经9d培育,可达到4079个/mL,的高密度.     

褶皱臂尾轮虫不同时期休眠卵的超微结构

分别用光学显微镜、扫描电子显微镜和透射电子显微镜对褶皱臂尾轮虫(Brachionusplicatilis)新产的和隔年的休眠卵形态结构进行观察。结果表明,两个时期的休眠卵外壳结构有区别,隔年卵外壳较薄,壳纹不明显;新卵外壳厚,壳纹明显。进行轮虫休眠卵分类时应以后者为准。新产休眠卵无气室,而隔年休眠卵有气室。进一步观察表明,休眠卵气室中的气体由休眠期间的代谢活动而产生。扫描电镜下,新产休眠卵有2层卵膜,隔年休眠卵有3层卵膜;透射电镜下,二者均为3层卵膜,不同时期休眠卵的每层卵膜厚度及细微结构有所差别。这两个时期的休眠卵胚胎结构上均有2层,但内含物有所不同。     

Effect of temperature on resting egg formation of the tropical SS-type rotifer Brachionus rotundiformis Tschugunoff

ABSTRACT:   Tropical minute rotifer strains (SS-type) induce mixis at 30–35°C but sexual reproduction and resting egg formation do not proceed well due to rapid environmental change. The present study examined the effect of temperature regulation on rotifer Brachionus rotundiformis (Langkawi strain, SS-type) resting egg formation in small (500 mL in culture volume)- and large-scale (500 L in culture volume) experiments. Rotifers were cultured at 30°C in 15–17 p.p.t. seawater with an initial density of 1 individual (ind.)/mL. After 4 days, when cultures were in exponential growth stage with active mixis induction, the culture temperature of the experimental rotifers was changed to 25°C. Control rotifers were cultured at 30°C throughout the experiment. Fresh or frozen Nannochloropsis oculata and condensed freshwater Chlorella vulgaris were used as the rotifer diets in the small- and large-scale experiments, respectively. Significantly higher resting egg production was observed with the experimental rotifers (30→ 25°C) versus the control rotifers. In the large-scale trial, experimental rotifers produced 2.6 × 10⁶ resting eggs during a 9-day experiment, which was 1.6-fold more than the control rotifers. Moreover, the efficiency of resting egg formation was found to increase by a factor of 1.8. The present study indicates that decreasing culture temperature from 30 to 25°C after active mixis increased resting egg formation in B. rotundiformis (SS-type).     

几种单胞藻对褶皱臂尾轮虫的营养强化研究

利用气相色谱法测定了小球藻、牟氏角毛藻、球等鞭金藻和投喂不同藻类后12h的褶皱臂尾轮虫的脂肪酸含量。试验结果表明,不论是投喂单种藻类还是2种混合藻类,强化后的轮虫其体内的脂肪酸含量均发生了明显变化,其中单链脂肪酸及低度不饱和脂肪酸的含量在投喂前后没有变化,各种脂肪酸的含量界于未强化的轮虫和所投喂的单胞藻饵料含量之间。3种高度不饱和脂肪酸的含量,除了二十二碳六烯酸因在牟氏角毛藻中含量较低,在单独投喂牟氏角毛藻后的轮虫中未检测出外,其余均与其所投喂的单胞藻的脂肪酸一致;轮虫中被检出的3种高度不饱和脂肪酸的含量,在单种藻类试验组中均低于所投喂藻类的含量;在2种藻类混合试验组中界于2种单胞藻含量之间。混合藻类比单种藻类强化轮虫具有更加全面的营养效果。     

绿色巴夫藻对褶皱臂尾轮虫的饵料效果试验

运用单体培育法和群体培育法研究了绿色巴夫藻(Pavlova viridis)等4种藻类对褶皱臂尾轮虫(Brachionus plicatilis)的饵料价值并测定了它们对褶皱臂尾轮虫被甲长、被甲宽和侧棘距的影响。结果表明,绿色巴夫藻和亚心形扁藻(Platymonas subcordiformis)的饵料效果分别明显地优于大溪地等鞭金藻(Tahitian Isochrysis aff.galbana)和小球藻(Chlorela sp.)(P<0.01),而绿色巴夫藻与亚心形扁藻之间及大溪地等鞭金藻与小球藻之间无显著差异(P>0.01)。不同藻类对褶皱臂轮虫的被甲长、被甲宽和侧棘距有极显著的影响(P<0.01)。     

Use of GABA to enhance rotifer reproduction in enrichment culture

Gamma‐aminobutyric acid (GABA) has been shown to enhance the reproduction of the rotifer Brachionus plicatilis Muller in stressful culture conditions. During the enrichment of rotifers for feeding to marine fish larvae, they are usually stressed as a result of exposure to different marine oils and high population densities. This typically results in decreased rotifer survival, reproduction and swimming activity. In the present study, we used GABA to increase rotifer reproduction and the swimming activity of rotifers in enrichment cultures. GABA treatment 24 h before high density enrichment enhanced reproduction during enrichment culture, but not when carried out simultaneously with enrichment. Swimming activity was not significantly affected by GABA treatment 24 h before or simultaneously with nutrient enrichment.     

海洋酵母培养褶皱臂尾轮虫的脂肪酸组成研究

以两株海洋酵母（Saccharomyces sp.和Rhodotorula sp.）培养褶皱臂尾轮虫（Brachionus plicatilis）,测定其脂肪酸组成。结果表明：轮虫具有一定的合成高度不饱和脂肪酸（HUFA）的能力,但其体内HUFA含量不足1％,仍需用富含HUFA的饵粒强化,才能满足海水仔稚鱼对HUFA的需要。     

Selectivity of the rotifer Brachionus plicatilis fed mixtures of algal species with various cell volumes and cell densities

The ability for food selectivity of rotifer Brachionus plicatiliswas studied in the laboratory by feeding mixtures of microalgae with various cell volumes. Chlorella sp. (≈22 µm³) was the reference algal species, and Asteromonas gracilis, (Chlorophyta) (≈2150 µm³), Tetraselmis suesica (≈268 µm³), Dunaliella salina (≈52 µm³) and Chaetoceros sp. (≈150 µm³) the experimental species. Each was mixed with Chlorella and fed in three experiments. In the first experiment, filtration and ingestion rates of rotifers each fed with algae revealed that the highest values were measured with the mixture of Chlorella + Asteromonas, and the lowest for Chlorella + Chaetoceros. In the second and the third experiments, by using several combinations of algal densities with the mixture of Chlorella + Asteromonas, a selectivity ability of the rotifers for Asteromonas was found. A hypothesis is presented that accounts for the preference of rotifers for Asteromonas, which is suggested as a new candidate species for use in live food production of fish hatcheries.     

酵母及藻类对褶皱臂尾轮虫培养效果的比较研究

采用种群累积培养法研究了两种酵母、两种藻类对褶皱臂尾轮虫的最适投喂密度。结果表明 ,这四种饵料对褶皱臂尾轮虫的最适投喂密度 (× 10 6cell·ml-1)分别是 :干酵母 ,15 ;鲜酵母 ,5 ;微绿球藻 ,4 5 ;三角褐指藻 ,2 0。同时 ,在最适密度下比较了这四种饵料对轮虫的培养效果。结果表明 ,四种饵料对轮虫的培养效果以微绿球藻为最优 ,其它依次为三角褐指藻 ,鲜酵母 ,干酵母。实验结果显示 ,褶皱臂尾轮虫批量培养及至工厂化培养的首选饵料是微绿球藻和三角褐指藻     

Growth, filtration and ingestion rate of the rotifer Brachionus plicatilis fed with large (Asteromonas gracilis) and small (Chlorella sp.) celled algal species

The rotifer Brachionus plicatilis was fed in experimental conditions with a small celled (2–5 μm) Chlorella sp. and a large celled (16–22 μm) Asteromonas gracilis algae. The specific growth rate (SGR) of rotifers fed Asteromonas (maximum 0.79) was statistically higher than that for rotifers fed Chlorella (maximium 0.61). The filtration and ingestion rates using different rotifer and algal densities exhibited certain maxima depending on the species, the cell density and the condition of the rotifers. The filtration rate was higher with Asteromonas and, although ingestion rate was lower than with Chlorella, the ingestion in terms of cell volume was 10‐fold higher. It seems that B. plicatilis ingests the larger cell diameter algal species more efficiently than the smaller species that is usually used for its mass culture.