虾夷扇贝(Patinopecten yessoensis)对铅和镉的生物富集与释放规律

利用双箱模型模拟了虾夷扇贝在混合暴露条件下富集、释放铅和镉的动力学特征,通过测定不同规格虾夷扇贝、不同组织富集、释放过程中铅和镉的含量并进行非线性拟合,获得不同生长阶段虾夷扇贝对铅和镉的生物富集系数BCF、吸收速率常数k1、释放速率常数k2、生物学半衰期B1/2以及不同组织中铅和镉的富集参数。结果显示,大、小两种规格虾夷扇贝对铅的BCF分别为1671、896,对镉的BCF分别为7433、1123;不同规格虾夷扇贝对铅、镉的BCF顺序为:大规格>小规格;相同规格虾夷扇贝BCF:镉>铅,表明虾夷扇贝对镉的富集能力强于铅;铅、镉的B1/2为:大规格>小规格,说明大规格的虾夷扇贝对铅、镉的代谢排出能力更强;铅在虾夷扇贝各组织中的富集顺序依次为:鳃>内脏团>闭壳肌,镉的富集顺序依次为:内脏团>鳃>闭壳肌。     

海湾扇贝对海水中镉的富集规律研究

本文利用原子吸收分光光度法研究镉暴露实验中海湾扇贝不同器官组织富集、排放镉的过程及影响因素。水体中镉通过被动扩散进入海湾扇贝鳃，根据吸附等温线并结合直线拟合结果得海湾扇贝鳃对镉的单层饱和结合量为2.12 μmol·g^-1 干重。鳃对镉的富集量和富集速率与水相中镉浓度成正相关关系，最高浓度组（2 μmol·L^-）的镉富集量和富集速率分别为(1.5±0.52) μmol·g^-1 干重和(0.375±0.13) μmol·（g·d）^-1。随着养殖时间的延长，海湾扇贝鳃、内脏和肌肉镉富集量逐渐增加，14 d（336 h）后，内脏和鳃中镉富集达到平衡，但肌肉中镉富集是否达到平衡，尚需进一步研究。盐度对海湾扇贝鳃、内脏和肌肉镉富集速率无显著影响（P>0.05）。富集在海湾扇贝体内的镉不断被排出，其中鳃的排放率最大，达到了38.3％，其次是内脏、肌肉。     

锌对海湾扇贝中镉累积和亚细胞分布的影响

采用室内模拟混合暴露方式,研究了在镉(Cd)质量浓度一定(0.05 mg/L)的条件下,添加不同质量浓度(0 mg/L、0.1 mg/L、0.5 mg/L、1 mg/L)的锌(Zn)对海湾扇贝整体、组织及亚细胞水平Cd累积和分布的影响。结果表明,Zn能显著抑制扇贝全贝对Cd的富集,并且这种抑制作用随暴露时间的延长和Zn浓度的升高而增强。在扇贝不同组织中Zn对Cd的富集均具有抑制作用,其中以鳃最为明显。在亚细胞水平,扇贝各组织累积的Cd主要分布在类金属硫蛋白(MTLP)和细胞碎片(CD)组分。在内脏各亚细胞组分中,Zn对Cd的抑制作用显著,且Zn的加入使CD中的Cd百分比从32%下降到21%~27%,而MTLP中的Cd百分比从57%增加到59%~67%。鳃组织中Zn对Cd百分比的影响更加明显,CD中Cd百分比从36%下降到14%~17%,MTLP中Cd百分比从59%增加到76%~79%;而性腺中MTLP和细胞器(ORG)组分中Cd百分比受Zn浓度影响较为明显,随着Zn浓度的升高,MTLP中Cd百分比下降,而ORG中Cd百分比升高;肌肉组织中Cd含量及百分比分布在亚细胞水平没有明显规律。     

虾夷扇贝(Patinopecten yessoensis)对铅和镉的生物富集与释放规律

利用双箱模型模拟了虾夷扇贝在混合暴露条件下富集、释放铅和镉的动力学特征,通过测定不同规格虾夷扇贝、不同组织富集、释放过程中铅和镉的含量并进行非线性拟合,获得不同生长阶段虾夷扇贝对铅和镉的生物富集系数BCF、吸收速率常数k1、释放速率常数k2、生物学半衰期B1/2以及不同组织中铅和镉的富集参数。结果显示,大、小两种规格虾夷扇贝对铅的BCF分别为1671、896,对镉的BCF分别为7433、1123;不同规格虾夷扇贝对铅、镉的BCF顺序为:大规格小规格;相同规格虾夷扇贝BCF:镉铅,表明虾夷扇贝对镉的富集能力强于铅;铅、镉的B1/2为:大规格小规格,说明大规格的虾夷扇贝对铅、镉的代谢排出能力更强;铅在虾夷扇贝各组织中的富集顺序依次为:鳃内脏团闭壳肌,镉的富集顺序依次为:内脏团鳃闭壳肌。     

栉孔扇贝不同组织中镉的微区分布特征及其变化规律

为阐明扇贝特异性富集镉(Cd)的机理,研究了栉孔扇贝不同组织中Cd的微区分布特征,并结合Cd的生物动力学实验研究了其变化规律。结果显示空白对照组栉孔扇贝内脏、鳃和性腺组织的Cd主要分布在类金属硫蛋白(MTLP)和细胞器中,闭壳肌组织中Cd主要分布在MTLP(占84.6%)。在Cd的富集实验中,内脏和鳃组织中MTLP和富含金属颗粒(MRG)中Cd的含量和所占百分比升高最显著,而细胞器中Cd的百分比明显下降;性腺组织中MTLP、细胞器和MRG组分中Cd的含量均明显升高,其中MRG中Cd的百分比升高,MTLP和细胞器中Cd的百分比逐渐下降;闭壳肌组织中MTLP和MRG中Cd的含量均显著上升,其中MRG组分中Cd的百分比显著升高。在释放Cd的实验中,内脏和鳃组织的MTLP中Cd的含量显著下降,而细胞器、热敏感蛋白(HSP)和MRG中Cd的含量和所占百分比逐渐升高,性腺组织各亚细胞组分中Cd含量均明显下降,但各亚细胞组分中Cd的百分比变化不明显;闭壳肌组织MTLP和MRG中Cd的含量下降,且MRG组分中Cd所占的百分比不断下降。本研究首次表明栉孔扇贝不同组织中Cd在亚细胞组分中的分布特征不同,并且在富集和释放Cd的过程中,内脏和鳃组织中的Cd在各亚细胞组分中不断发生调节和重新分配。     

镉对海湾扇贝的急性毒性研究

利用水生生物毒性试验方法,分5个浓度进行镉对日照海域海湾扇贝的急性毒性实验,以期对日照海域海湾扇贝养殖提供理论依据。利用概率单位和浓度对数作线性回归,得出镉对海湾扇贝(Argopectenirradiams)在24、48、96h的半致死量LC50,其值分别为5.85、4.52和3.45mg/L。并计算出镉对海湾扇贝的安全质量浓度为0.0345mg/L。实验证明,Cd对海湾扇贝是剧毒性的毒物,海湾扇贝发育越往后期,它对Cd的耐受性就越大。     

栉孔扇贝对铜、铅、镉的累积效应

试验结果表明:当常规理化指标一致时,随着Cu、Pb、Cd质量浓度的升高,栉孔扇贝各组织的蓄积量明显升高;Cu、Cd在扇贝组织中蓄积量是内脏团>鳃>肌肉,Pb在扇贝组织中的蓄积量是鳃>内脏团>肌肉;当Cu、Pb、Cd质量浓度(0.1 mg/L)相同时,其鳃、内脏团、肌肉中重金属蓄积量的上升速率是Cu>Cd>Pb。     

栉孔扇贝对重金属的富集效应研究

2009年6-12月在烟台四十里湾某栉孔扇贝养殖区进行现场监测,研究结果表明,栉孔扇贝对重金属的富集有明显的选择性,对Cd的富集系数高达25 495,对铜富集系数为1 453,对铅的富集系数为258。对镉的富集与其生长周期呈显著正相关,而Cu、Pb随其生长时间的增加在体内的增加趋势并不明显。栉孔扇贝各组织中重金属Cd的含量具有明显差异,闭壳肌中Cd含量仅为内脏团中的1/5。研究发现,栉孔扇贝的主要饵料浮游植物对重金属Cd的富集效率远大于Pb、Cu,滤食浮游植物是栉孔扇贝富集重金属的主要途径。文中还对栉孔扇贝的人体消费标准进行了初步研究,给出了人体消费参考量。     

2株海洋细菌对镉的吸附作用

用高质量浓度镉培养液单独和联合培养2株海洋细菌J2和J6,3、7、10、14、17d后,采用原子吸收法分别测定培养液上清液和菌细胞中Cd2+的质量浓度,以确定2株菌对镉的吸附性能;通过测定菌体细胞内半胱氨酸脱巯基酶的活性,初步研究了2株菌对镉的转化作用机理。试验结果表明,2株菌均可将细胞外的Cd2+吸收到细胞内,在培养至第7d时,上清液中Cd2+的含量达到最低值,随着培养时间的增加逐渐趋于稳定,J2和J6菌体细胞中Cd2+的含量分别在培养到第10d和14d时达最大值,联合培养对镉的吸附作用优于单独培养;J2和J6在镉处理后细胞内的半胱氨酸脱巯基酶活性均显著增高,提示Cd2+的吸附与细胞内半胱氨酸脱巯基酶作用产生的S2-有关。     

镉对海湾扇贝的急性毒性研究

利用水生生物毒性试验方法,分5个浓度进行Cd2 对海湾扇贝的急性毒性实验,利用概率单位和浓度对数作线性回归,得出Cd2 对海湾扇贝在24、48、96小时的半致死量LC50,其值分别为5．85、4．52、3．45mg/L。并计算出Cd2 对海湾扇贝的安全质量浓度为0．0345 mg/L。     

Alleviation effect of dietary cerium and its complex with chitosan oligosaccharide on cadmium accumulation in juvenile turbot,Scophthalmus maximus L., under cadmium stress

An 8 weeks feeding trial was conducted to investigate the effect of dietary cerium (Ce) and its complex with chitosan oligosaccharide (COS‐Ce) on growth performance and cadmium (Cd) accumulation of turbot, Scophthalmus maximus L. under Cd stress. The basal diet (Diet 0) was formulated without Cd and cerium as the control. Seven other experimental diets (Diets 1–7) were formulated with supplementation of 50 mg Cd²⁺/kg feed, 50 mg Cd²⁺/kg and 50 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 100 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 200 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 50 mg COS‐Ce/kg feed, 50 mg Cd²⁺/kg and 100 mg COS‐Ce/kg feed, and 50 mg Cd²⁺/kg +200 mg COS‐Ce/kg feed. Results of the present study showed that, compared with the control group, the condition factor in fish fed the diet with 50 mg Cd²⁺/kg feed (Diet 1) was significantly lower, whereas the Cd concentration in liver and kidney of fish fed the diet with 50 mg/kg Cd²⁺ (Diet 1) was significantly higher (P < 0.05). The high Cd accumulation of fish fed diets with sole 50 mg/kg Cd (Diet 1) could be significantly decreased by 51.72% after supplementation of 200 mg COS‐Ce/kg in the diet (Diet 7). These results suggested that elevated COS‐Ce could effectively protect against dietary Cd accumulation in turbot.     

Oxidative damages by cadmium and the protective effects of low‐molecular‐weight chitosan in the freshwater crab (Sinopotamon yangtsekiense Bott 1967)

Cadmium (Cd) is an environmental pollutant and has posed a potential threat for the growth and survival of freshwater crabs. Low‐molecular‐weight chitosan (LMWC) may promote growth in crab culture. The present study was designed to investigate the Cd‐induced oxidative damage and the protective role of LMWC against oxidation caused by Cd²⁺ in freshwater crab (Sinopotamon yangtsekiense Bott 1967). The results showed that Cd²⁺ significantly inhibited the activities of total antioxidant capacity, superoxide dismutase, catalase, glutathione peroxidase and peroxidase, while it increased malondialdehyde levels in the hepatopancreas and the gill. Moreover, Cd²⁺ at the concentration tested obviously increased the protein carbonyl contents and DNA–protein crosslinks coefficients in the hepatopancreas, gill, heart and muscle tissues of S. yangtsekiense in a dose‐dependent manner. In addition, Cd²⁺ induced a significant increase in the levels of nitric oxide and inducible nitric oxide synthase in the hepatopancreas, gill and muscle. The results also showed that LMWC plus Cd²⁺ significantly improved antioxidant markers. The observations suggested that the severe oxidative damage in multiple crab tissues was one of the important causes of the adverse influence of Cd²⁺ on S. yangtsekiense growth and indicated that LMWC could provide a protective effect against such an injury.     

Preliminary study on zeolite materials used to control of heavy metal pollution during the culture of mud clam Tegillarca granosa L.

To control heavy metal pollution during the culture of the mud clam, Tegillarca granosa L., the isothermal static adsorption capacities of three adsorption materials [natural zeolites, zeolites synthesized from kaolin and zeolites synthesized from coal fly ash (ZFA)] towards Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ in seawater were investigated. The adsorption capacity of the best material was investigated during the culture of mud clam in an artificially polluted environment. Results showed that the ZFA adsorption capacity was the highest and conformed to the Freundlich model. The theoretical maximum adsorption capacities of the adsorbent towards Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ in seawater were 3.057, 1.123, 0.325, 13.101, 6.116 mg g^?1 and 6.527 μg g^?1 respectively. For seawater artificially polluted by six heavy metals, heavy metal adsorption by ZFA followed the order Zn²⁺ > Cd²⁺ > Hg²⁺ > Cu²⁺ > Pb²⁺ > Cr⁶⁺. For the mud clam culturing experiment that simulated a continuously polluted water source, the Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ contents of mud clam tissues decreased by 40.9%, 25.8%, 9.6%, 28.2%, ?27.8% and 25.7%, respectively, after 21 days of culturing compared with the contents before the experiment.     

Mechanism of Cd<Superscript>2+</Superscript> on DNA cleavage and Ca<Superscript>2+</Superscript> on DNA repair in liver of silver crucian carp

The subject of acute injury, apoptosis and canceration of animals induced by heavy metal ions has been one of the hotspots studied worldwide. However, the exact molecular mechanism of Cd-induced carcinogenicity remains largely unclear, and how to relieve the toxicity in vivo has rarely been reported. For this paper, we have investigated the mechanism of Cd²⁺ on DNA cleavage and Ca²⁺ on DNA repair in the liver of silver crucian carp (Carassius auratus gibelio) by agarose gel electrophoresis methods and by estimating biochemical indexes. Our results show that Cd²⁺ induces the classical laddering degradation of DNA in vivo and that DNA cleavage is repaired after injection with Ca²⁺ under various Cd²⁺ concentrations. DNA cleavage caused by Cd²⁺ is due to the activation of deoxyribonuclease (DNase) and the accumulation of reactive oxygen species (ROS). Furthermore, Cd²⁺ destroys the antioxidant system, which diminishes the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), causing an increase of the lipid peroxidation (LPO) level, respectively. However, after the liver is injected with Ca²⁺ under various Cd²⁺ concentrations, the DNase activity, the ROS generating rate and the LPO level are obviously reduced, the activities of SOD, CAT, and POD are greatly increased. At the same time, ROS production and removal recoves its balance. The results show that Ca²⁺ can relieve the toxicity of Cd²⁺ in silver crucian carp.     

壳聚糖对Cd2+和Pb2+的吸附作用

为开发新型吸附剂,降低重金属对水体的污染,研究了壳聚糖对Cd²⁺和Pb²⁺的吸附条件,探讨了pH、温度、反应时间、壳聚糖添加量和金属离子初始浓度等因素对壳聚糖吸附性能的影响。结果表明,pH 7~8和pH 5~6条件下壳聚糖对Cd²⁺和Pb²⁺的吸附能力最强;低温有利于壳聚糖的吸附;在8 h时壳聚糖对Cd²⁺的吸附容量达到最大,而对Pb²⁺的吸附在实验时间内是随着吸附时间的延长而增大;随着壳聚糖添加量的增加,其对Cd²⁺和Pb²⁺的吸附能力也增强;初始金属离子浓度的变化对Cd²⁺的影响不大,而在高的金属浓度下对Pb²⁺的吸附率显著降低。壳聚糖对Cd²⁺、Pb²⁺的吸附动力学和热力学分别符合Lagergren方程二级吸附模型和Langmuir吸附方程。研究表明,壳聚糖对不同金属离子的吸附能力不同,在单一金属溶液中,壳聚糖对Cd²⁺的吸附能力要强于对Pb²⁺的吸附能力。系统地研究了壳聚糖对Cd²⁺和Pb²⁺的吸附条件及性能,为壳聚糖作为重金属吸附剂的应用提供理论依据。     

A high amylase‐producing bacterial strain exhibiting the phosphorus‐dissolving ability,isolated from freshwater aquaculture pond

Amylase‐producing bacteria could improve water quality contaminated by waste from feed residue and fish metabolism, thereby increasing the efficiency of aquaculture systems. The objective of this research was to screen and optimize fermentation conditions of a high amylase‐producing strain. Four amylase‐producing bacterial strains (named S458‐1, G05, H38 and B09) were isolated from a grass carp pond, and the strain S458‐1 showed the highest amylase‐producing ability, with 19.58 ± 0.38 mm hydrolysis circle diameter. The strain S458‐1 was identified as Bacillus cereus based on morphological identification, biochemical identification and 16S rDNA sequence analysis. The optimal culture medium formula included (in g/L) Ca²⁺ 0.8, Mg²⁺ 0.2, Mn²⁺ 0.4, Fe²⁺ 0.6, Al³⁺ 0.2, 1% soluble starch and 1% peptone. The optimal fermentation conditions were determined as initial pH 9, culture temperature 37°C, fermentation time of 60 hr and 2% inoculum. Under the optimal formula and condition, its enzyme activity increased from 32 U/ml to 173.01 U/ml, a 5.41‐fold increase. Surprisingly, our research found that the strain S458‐1 also had phosphorus degradation capabilities. Its phosphorus‐dissolving ability was both time‐ and concentration‐dependent. Thus, this study will make a contribution to the bacterial amylase based on the fermentation process and provide a theoretical basis for further research of aquatic probiotics.     

蛋白水解肽-Fe2+配合物对克氏原螯虾体内Cd2+的脱除效果

为探讨克氏原螯虾体内重金属Cd²⁺残留的脱除方法,采用基础饲料中添加制备的蛋白水解肽-Fe²⁺配合物(TPH-Fe²⁺)进行饲喂,检测螯虾不同组织器官中Cd²⁺含量变化情况。结果显示,染毒后螯虾不同器官中Cd²⁺富集量依次为内脏团>肠>鳃>腹部肌肉>螯足肌肉,且在0~12 d自然净化过程中,无显著性下降趋势。添加400、800和1 200 mg/kg TPH-Fe²⁺饲喂螯虾,内脏团、鳃、肠及腹部肌肉中Cd²⁺含量均有不同程度下降;饲喂12 d后,螯虾不同器官中Cd²⁺脱除率为肠>内脏团>鳃>腹部肌肉,脱除率分别为40.60%、36.13%、33.36%和10.15%;TPH-Fe²⁺对螯虾螯足肌肉中Cd²⁺含量无显著性影响。研究表明,蛋白水解肽-Fe²⁺配合物能有效脱除螯虾体内Cd²⁺残留,可作为一种螯虾养殖饲料添加剂在基础饲料中加以应用。     

Colonization of the gut in first feeding turbot by bacterial strains added to the water or bioencapsulated in rotifers

Two bacterial strains, 4:44 and PB52, isolated from turbot(Scophthalmus maximus L.) were used during a first feedingexperiment with turbot larvae. Bacteria were either added directly tothe water on the day of hatching of the larvae (day 0), orbioencapsulated in rotifers (Brachionus plicatilis) distributedon day 2 after hatching. The two bacterial strains were found to bepresent in the water of the rearing tanks throughout the experiment. Theaddition of bacteria influenced the species-composition of themicroflora associated with intensively produced rotifers added to thetanks, and resulted in colonization of the gut of the larvae by theadded bacterial strains. The strain 4:44 showed a peak on day 9 afterhatching, and reached a mean(sem) of 2.5(1.4) × 10⁴bacteria per larva, when added in a mixture with PB52, and 0.4(0.1)× 10⁴ bacteria per larva, when added alone. The strainPB52, on day 12 after hatching, reached 5.2(1.5) × 10⁴bacteria per larva when added in a mixture with strain 4:44, and12.5(0.7) × 10⁴ bacteria per larva, when added alone.The added bacteria colonized the gut turbot larvae, whereas thebacterial land, the survival and growth of the larvae were in most casesnot influenced in a negative way by the addition of bacteria.     

Probiotic characteristics and aflatoxin B1 binding ability of Debaryomyces hansenii and Kazaschtania exigua from rainbow trout environment

The aim of this study was to evaluate probiotic properties and the aflatoxin B₁ adsorption ability of yeasts isolated from rainbow trout intestine and fish feed to assess their use in the formulation of feed additives. Growth at pH 2, bacterial pathogens inhibition, bacterial pathogens co‐aggregation, autoaggregation, homologous and heterologous inhibition against lactic acid bacteria were evaluated. Moreover, aflatoxin B₁ adsorption was tested. All strains were able to maintain viable (10⁷ cells/ml) at pH 2. All strains isolated from intestine were identified as Kazaschtania exigua, while strains isolated from feed were all identified as Debaryomyces hansenii. Kazaschtania exigua RC035 and RC037 showed the strongest antimicrobial activity while K. exigua RC037 and RC038 were the most efficient co‐aggregating bacterial pathogens. All strains exhibited strong autoaggregation. None of the tested yeast strains showed homologous inhibition towards other yeasts and heterologous inhibition towards lactic acid bacteria strains. Debaryomyces hansenii RC031 demonstrated aflatoxin B₁ adsorption capacity (21%). The results of the present study indicate that select strains of Kazaschtania exigua and D. hansenii showed potential to improve the health of rainbow trout by inhibiting pathogens and binding AFB₁ and their use as probiotics may improve the production of rainbow trout in aquaculture systems.